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This article was downloaded by: [Litsinger, J. A.]On: 1 May 2009Access details: Access Details: [subscription number 910450850]Publisher Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK
International Journal of Pest ManagementPublication details, including instructions for authors and subscription information:http://www.informaworld.com/smpp/title~content=t713797655
Comparison of insect pest complexes in different Philippine dryland riceenvironments: population densities, yield loss, and managementJ. A. Litsinger; E. M. Libetario a; A. T. Barrion a; R. P. Apostol ba Philippine Rice Research Institute (PhilRice), Maligaya, Science City of Muoz, Nueva Ecija, Philippines b
International Rice Research Institute, Metro Manila, Philippines
Online Publication Date: 01 April 2009
To cite this Article Litsinger, J. A., Libetario, E. M., Barrion, A. T. and Apostol, R. P.(2009)'Comparison of insect pest complexes indifferent Philippine dryland rice environments: population densities, yield loss, and management',International Journal of PestManagement,55:2,129 149
To link to this Article: DOI: 10.1080/09670870802604054URL: http://dx.doi.org/10.1080/09670870802604054
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Comparison of insect pest complexes in different Philippine dryland rice environments:population densities, yield loss, and management
J.A. Litsingera*, E.M. Libetariob, A.T. Barrionb and R.P. Apostolc
a1365 Jacobs Place, Dixon, CA 95620, USA; bPhilippine Rice Research Institute (PhilRice), Maligaya, Science City of Munoz,Nueva Ecija, 3119, Philippines;
cInternational Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines
(Received 12 February 2008; final version received 5 November 2008)
In the Philippines most of the dryland rice pests are distinct from those of wetland culture. Partitioned-growth-stage yield loss studies revealed the highest losses in dryland rice were due to sown-seed and seedling pests (ants,field crickets, mole crickets, and termites) as well as root feeders (white grubs and root aphids) and early seedlingpests (seedling maggot and flea beetle) more than the common foliar wetland pests. Losses (571%) were highestin the sites with the smallest rice area in which pests were concentrated and the poorest soils (which constrain yield
compensation) along a continuum of dryland rice habitats. Crop management practices such as overseeding andfertility management can mitigate potential losses to a large degree. Therefore integrated crop management playsa central role in integrated pest management in dryland rice cultivation where the use of insecticides should beminimized for economic and environmental reasons.
Keywords: rice insect pests; yield loss; slash and burn; upland rice; integrated crop management; pestmanagement; crop compensation
1. Introduction
Dryland rice is a cultural type distinct from the
more common wetland culture where direct rainfall
is the only source of water and japonica-based
varieties, rather than indica ones, are normallycultivated in non-bunded fields. Dryland rice,
representing ca. 13% of rice area worldwide (Gupta
and OToole 1986), is neither puddled nor ponded
and the soils are aerobic (Morris 1986). The
Philippines ranks fifth among SE Asian countries
in dryland rice area (Gupta and OToole 1986); it
supports 15% of the Filipino population (Garrity
et al. 1993).
Arraudeau and Harahap (1986) conducted a
worldwide survey among dryland rice scientists and
produced a long list of constraints beginning with
poor soil, frequent water stress, fungal diseases,
nematodes, weeds, and lack of adaptive and manage-
ment responsive varieties. They also listed a wide
array of insect and vertebrate pests that contribute to
low yields, but these were considered of lesser
importance. Grist and Lever (1969) and Fujisaka
et al. (1991) also mentioned birds, rodents, wild pigs,
monkeys, squirrels and even elephants and rhino-
ceroses as dryland rice pests, particularly near forests
which are habitats for most of these animals. The
degree to which the aforementioned pest constraints
are manifested is mainly linked to the type of dryland
habitat; the latter can vary dramatically in terms of
slope, soil type, rainfall pattern, and surrounding
crops and flora.
Litsinger et al. (1987b) reviewed the world
literature on dryland rice insect fauna and noted
life-history strategies based on polyphagy, dormancy,and/or dispersal abilities, as dryland rice is dom-
inantly a single rice crop system. Key insect pests of
the wetlands, i.e. brown planthopper Nilaparvata
lugens (Sta l), green leafhopper Nephotettix virescens
(Distant), and yellow stemborer Scirpophaga incertu-
las (Walker), are specific to Oryza spp. and cannot
sustain themselves in a dryland rice environment. Due
to the short rice season, they must re-migrate each
season from nearby wetland sites. Several soil insects
common in the drylands have life-cycles of up to a
year or more in duration. More dryland rice pests
enter periods of dormancy than wetland pests.
Armyworms, butterflies, and locusts have greater
dispersal powers than most wetland insect pests, with
the exception of rice planthoppers and leaffolders
(Denno et al. 1991).
In the Asian literature, there have been few trials
in which yield losses were measured, but all research-
ers used the insecticide check method. Other yield loss
studies have been conducted in Latin America and
Africa where dryland rice is the most important rice
culture (Litsinger et al. 1987b). In Thailand, Kata-
nyukul and Chandartat (1981) recorded losses of only
5% (range 113%) from 1976 to 1979.
*Corresponding author. Email: [email protected]
International Journal of Pest Management
Vol. 55, No. 2, AprilJune 2009, 129149
ISSN 0967-0874 print/ISSN 1366-5863 online
2009 Taylor & Francis
DOI: 10.1080/09670870802604054
http://www.informaworld.com
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Earlier studies in the Philippines documented the
insect pest fauna and measured losses by the
insecticide check method in Batangas and Camarines
Sur provinces (IRRI 1975, 1976a). Those studies were
undertaken in habitats with favourable soils and
more permanent agriculture based on thoroughtillage. Losses incurred by traditional tall Dagge
and Kinanda varieties were very high, averaging
31 + 17% (2.4 vs. 1.8 t/ha) over nine fields. Studies
were also carried out in dryland fields on the border
of the irrigated experimental farm of the Interna-
tional Rice Research Institute (IRRI), the conclusion
being that most insects found in the drylands were
also present in the wetland area (Pathak and Dyck
1975).
There is a continuum of dryland rice habitats that
represents stages in settlement, economic develop-
ment, and population growth in a locality (Litsinger
1993). It begins with pioneering farmers settling intorecently logged rainforests; they then cultivate dry-
land rice by slash and burn or swidden agriculture
(Morris 1986). As the area becomes more densely
populated, animal power is used to pull tillage
implements. Still further population increase brings
nearby markets and crop diversity increases where
cash crops are rotated with rice.
In this report we argue that each of these
successive stages in land use leads to different pest
complexes and population intensities. We also expand
on earlier trials in the Philippines. Multi-year crop
loss assessments were undertaken in four farmcommunities, each representing a different environ-
ment along the continuum. These differed from
previous studies as losses now were partitioned by
rice growth stage. Also more attention was given to
recording pest complexes, as researchers lived at the
site as opposed to making periodic visits, and so
sampling could be done more frequently. We also
report on the results of trials which were also
undertaken to develop practical crop production
practices centred upon cultural controls as well as
minimal usage of insecticides following an integrated
crop management approach.
2. Materials and methods
2.1. Site descriptions
Two research sites (Claveria and Tupi) were estab-
lished in Mindanao Island under the influence of the
Inter-tropical Convergence Zone climate, and a
further two were established in Luzon Island (Sinilo-
an and Tanauan) with a monsoon climate. Together,
all sites represented an environmental and crop
cultural continuum from subsistence, low input, slash
and burn systems on sloping, acidic, and eroded soils
sown with traditional varieties, to high input,diversified agriculture on flat volcanic soil sown
with modern rice and cash crops.
2.1.1. Siniloan
This slash-and-burn site was established in Magsay-
say village located mid-way between Siniloan and
Real municipalities in the Sierra Madre mountains of
the Laguna and Quezon provincial border in highlyeroded, acidic soils (Gonzaga et al. 1986). Traditional
rice is sown in holes made with a dibble stick in July
among smouldering tree stumps. Rice fields are small
(ca. 0.1 ha) due to the high labour demands, as
perennial grasses quickly invade requiring tedious
hand-weeding. Farmers do not use either inorganic or
organic fertiliser.
2.1.2. Claveria
Claveria in Misamis Oriental province, near Cagayan
de Oro City, is located on an escarpment along the
lower slopes of Mt Balatukan volcano. This highlyeroded and acidic soil site is representative of a
recently deforested stage; the forest has been replaced
by perennial grasslands, leaving only scattered trees
in a relatively steep terrain. The farmers priority is to
first plant maize in fields prepared by animal-drawn
implements including the mouldboard plough. Rice is
sown in rows in May or June made with a furrow
opener which also serves for inter-row cultivation of
weeds in the early growth stages. There is more
uncultivated than cultivated land in the site. Farmers
have their own tall, traditional japonica type varieties,
which they cultivate with few purchased inputs.Further site description can be found in Litsinger
et al. (2002).
2.1.3. Tupi
Tupi is a town in South Cotabato province, lying on
favourable, young, and only slightly acidic volcanic
soils. This third stage is more populated and on flat
terrain with few uncultivated areas (IRRI 1990).
Farmers typically apply 30 kg/ha of N and P;
uncharacteristically for dryland rice sites, farmers
grow a mix of modern semi-dwarf varieties along with
high value traditional types.
2.1.4. Tanauan
The principal crops in Cale village, Tanauan town in
Batangas province are maize and dryland rice as well
as a wide array of vegetables for the nearby Manila
market. The nearby Taal volcano erupts regularly to
spread new ash over the landscape. This fourth stage
represents a highly favourable soil in a populated area
where farmers engage in the growing of high-input,
diversified croppings where fields are intensively tilled
(IRRI 1976b). The topography is gently sloping,and farmers prevent the slight erosion with living
fencerows. Farmers are economically well off from
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the sale of vegetables, and can afford an average of
110 kg N/ha on rice where lodging can occur during
ripening stage during typhoons. Due to its preferred
taste and grain type, farmers prefer to grow a
traditional variety rather than to purchase rice in
the market.
2.2. Rice crop management
UPLRi5 dryland rice variety bred by the University
of the Philippines was used in all sites except Siniloan.
This semi-dwarf is a cross between indica and japonica
types, and is high tillering and of medium maturity
(130140 d). The traditional rice Benernal in Siniloan
was grown at a seeding rate of 50 kg/ha whereas in
other sites the rate was 100 kg/ha. Siniloan farmers
placed three to four seeds per dibble hole 2025 cm
apart. Each hole was covered with soil and stepped
on. All trials were superimposed on farmers fieldsunder their own agronomic management. In addition
to yield loss treatments, the trials included some
improved agronomic practices in the experimental
design. In all but the slash and burn site, land was
tilled with animal-drawn ploughs. Furrows were
made with a wooden implement (lithao), and seed
was broadcast and raked into the furrows with a
spike-toothed, box-harrow and covered by a final
levelling. In Tanauan 90 kg N/ha was applied in two
equal splits as a side dressing during hilling up and at
panicle initiation. Prior to seeding in Claveria and
Tupi, P was placed in the open rows at 25 kg/ha andcovered. A side dressing of 25 kg N/ha occurred at
14 d after crop emergence (DE) before the first inter-
row cultivation followed up by a second top dressing
of 25 kg N/ha before panicle initiation. Farmers
hand-weeded as needed. In Tanauan and Tupi
farmers undertook dry season ploughing for weed
control, in the latter site a number of times. No
cooperating farmer applied any pesticide to dryland
rice crops. Grain yield was taken from five samples of
5 m2 cuts taken in a stratified grid within the 100-m2
plots. The grain was dried to 14% moisture.
2.3. Treatment descriptions
2.3.1. Partitioned-growth-stage yield loss trials
The insecticide check, partitioned yield loss method
was conducted following Litsinger et al. (1980). There
were eight treatments in Claveria (seven seasons) and
Tupi (four seasons) to quantify losses in six growth
stages. The first treatment was termed the complete
control where the objective of a regimen of insecticide
applications was to suppress all groups of insect pests.
Sown seeds were protected with a systemic insecticide
(6 g a.i. carbosulfan STD/kg seed) from ants, field
crickets, and mole crickets as well as seedling maggotand flea beetles that attack young seedlings. Carbo-
sulfan was added to cassava flour then mixed into a
paste. Seeds were then added to be coated with the
mixture, and finally they were dusted with cassava
flour for easier handling after drying overnight. Next,
a soil insecticide (1 kg a.i. Lindane (gBHC) granules/
ha) was placed in the seed furrows directed against
root-feeding white grubs and termites, and a secondapplication was side-dressed at hilling up. Litsinger
et al. (1983) showed that this insecticide had high
efficacy against white grubs. Reproductive stage soil
protection was 0.75 kg a.i. carbofuran granules/ha
placed in shallow furrows 40 and 70 DE for root-
feeding aphids and mealybugs. The reproductive stage
was also protected by an additional treatment of
weekly foliar sprays (0.4 kg a.i. monocrotophos/ha)
for stemborers, plant- and leafhoppers, and leaffolders.
Ripening stage protection against rice seed bugs was
10 g a.i. deltamethrin EC/ha sprayed twice weekly
from panicle emergence to hard dough. The second
treatment was an untreated check. Foliar insecticideswere applied in 19 l, lever-operated, knapsack
sprayers fitted with cone nozzles. Spray volume
increased from 300 to 500 l/ha as the crop grew.
Each of a succession of treatments eliminated one
of the complete control treatments in order to
partition the loss among growth stages. Rice growth
stages were described by Yoshida (1981). The third
treatment eliminated the seed treatment, the fourth
eliminated the soil applications of gBHC granular
insecticide, the fifth eliminated the reproductive stage
carbofuran granules, the sixth eliminated the repro-
ductive stage sprays, and the seventh treatmenteliminated ripening stage sprays.
In Tanauan, yield loss was calculated in the tall
traditional Dagge rice over five seasons in separate
experiments and from the improved UPLRi5 rice in
experiments over three seasons. The partitioned yield
loss treatments consisted of a complete control which
protected five growth stages. The first stage was the
sown-seed where 4 g a.i. bendiocarb/kg seed made as
a water slurry without the cassava flour. A soil
treatment consisted of diazinon granules at 1 kg ai/ha
applied in the seed furrows. A third was vegetative
foliar protection with 1 kg a.i. monocrotophos/ha
sprays at 10-day intervals (25, 35, 45 DE) and the
follow on to protect the reproductive stage (55, 65, 75
DE), and then by 1 kg a.i. gBHC EC/ha at milk, soft,
and hard dough stages.
The complete control treatment in Siniloan (two
seasons) included increasing the dosage of the seed
treatment to 0.4 kg a.i. carbosulfan/ha. This was
followed by weekly sprays of foliar insecticides:
0.75 kg a.i. monocrotophos/ha during the vegetative
and ripening stages and the mixture of 0.75 kg a.i.
chlorpyrifos BPMC/ha from panicle initiation to
heading. Only the total yield loss was determined in
Siniloan where the complete control was compared tothe untreated check, as no growth stage partitioning
was carried out to keep the trials small.
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Total yield loss was calculated as the difference
between the complete control treatment and the
untreated check. To calculate percentage, total loss
was divided by the full protection yield and multiplied
by 100. Yield losses from each of the partitioned-
growth-stage treatments where insecticide wasomitted were calculated in the same way and then
added. As the two totals were seldom mathematically
equal, losses for each pest group or crop stage were
apportioned based on the total loss from the complete
control.
2.3.2. Crop management treatments
Plots of integrated crop management practices were
randomised among the yield loss plots in the on-farm
trials. Their purpose was to generate recommenda-
tions for farmers, and their inclusion each season
allowed an iterative process of technology develop-ment for each site. These treatments included varia-
tions in seeding rate, inorganic and organic fertiliser,
and insecticide protection either as soil and/or seed
treatments.
Six potential recommended practices were com-
pared in Siniloan: (1) was a high input practice to
determine the yield potential that involved organic
fertiliser plus lime mixed into the soil in each dibble
hole to raise soil pH thus making applied P more
available in the highly acidic soils. Insect control was
an insecticide seed treatment (0.25 kg a.i. carbosulfan
ST/kg seed). The seeds were slightly moistened toallow the seed treatment (ST) formulation to stick to
the seed coat. Foliar insecticide protection was
0.75 kg a.i. monocrotophos EC/ha weekly during
the vegetative stage to flowering, and 0.75 kg a.i.
Brodan EC (BPMC chlorpyrifos)/ha during milk,
soft dough, and hard dough. (2) The same as
(1) except it lacked the seed protection. (3) This
included only the insecticide seed treatment plus ash
placed in the seed holes plus 23 kg N/ha from urea
applied on the soil surface 14 DE. (4) This consisted
only of the ash and 23 kg N/ha. (5) This received the
seed treatment plus the ash. (6) This consisted only
the seed treatment. (7) The untreated check (i.e.
control).
In Tupi and Claveria similar treatments were
compared which involved two seeding rates (50 and
90 kg/ha) and a soil insecticide treatment 0.25 kg
a.i. Lindane G/ha and an insecticide seed treatment
(0.3 kg a.i. carbosulfan ST/ha). Two fertiliser
treatments also were compared: the first lacked
inorganic fertiliser; the second was 50-25-0 with the
N application split at 14-25 DE during inter-row
cultivation and before panicle initiation, and P was
applied basally during land preparation. The inclu-
sion of these treatments varied from season toseason to enable us to find the best performing
treatment.
In Tanauan a crop management trial was con-
ducted in 1976 with 12 treatments replicated in six
farmers fields. Four of the treatments involved
incremental increases in the seeding rate from 50 to
125 kg/ha. Four other treatments were conducted
at 50 kg seed/ha that tested two seed and twosoil treatments. The seed treatments tested two
chemicals carbofuran ST and dieldrin WP both
at 0.5 kg ai/ha dosages. The two soil treatments were
carbofuran G at 0.5 and 2 kg ai/ha dosages. Two
other treatments tested the seed treatments at a higher
seeding rate of 100 kg/ha while the last two treat-
ments tested the soil insecticide dosages, again at the
100 kg seed/ha. Data taken were plant stand (ten 3-m
row samples) and yield (two 10 m2 cuts).
A follow-up trial was conducted in four farmers
fields over 3 years (19781980) with UPLRi5 sown at
100 kg/ha where a seed (0.30 kg a.i. carbosulfan ST/
ha) and a soil (0.75 kg a.i. diazinon G/ha) treatmentwere compared to an untreated check. Crop manage-
ment treatments were analyzed economically to
determine marginal returns and benefit:cost ratio
(B:C) following the method of Smith et al. (1988)
using 1986 prices for agricultural inputs and including
a 12% interest per annum for inputs and labour
priced at $0.10h, the wage in rural Philippines at the
time. Unmilled rice was valued at $0.128/kg. A B:C
ratio of 42 is considered a favourable return on
investment.
2.4. Experimental design
Field trials were conformed to a randomised complete
block design with farmers as replicates. New farmer
cooperators were selected each season, as the results
would become recommendations for the farm com-
munity as a whole. Farmer cooperators were selected
on a staggered basis evenly along each seasons
planting curve. Plot sizes were 100 m2 with the
exception of the slash and burn site, where they
were 10 m2, the largest obtainable size of uniform
field conditions free of tree stumps.
2.5. Arthropod and crop sampling
Identification of arthropods was undertaken by one
of us (ATB). Voucher specimens were deposited in
the IRRI Entomological Museum. On each sampling
date a team of at least two staff participated in data
collection. The stratified grid method was used to
sample plants or arthropods from each quadrant of
all plots. Data collection sites were randomly selected
within each quadrant. One person recorded the data
on a clipboard while others did the counting with
mechanical tally counters. Plant stand was recorded
weekly from the first through the fourth weeks bycounting the number of plants along the row
measured in 14-m sections. Insect damage was also
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assessed at the same time. Seedling maggot was
censused by damaged tillers (deadhearts) and mole
cricket by damaged plants. Root pests such as
termites, root aphids, and mealybugs were recorded
in 50 plant samples with each plant being uprooted
and the root system inspected. Stemborer deadheartsand whiteheads as well as leaffolder damaged leaves
were censused 50, 70, 90, and 110 DE from 10
samples of 5-m rows. In these cases the number of
tillers and leaves was counted in each 5-m row. Plant-
and leafhoppers were sampled in the crop in Tanauan
using a motorized D-VAC1 suction machine that was
swung side to side a distance of 1 m and walked a
measured 25 m to give a sample size of 25 m2.
Sampling was done weekly in four fields from early
vegetative stage to 2 weeks before harvest. Rice seed
bugs were sampled by taking 25 pendulum sweeps
with a 38-cm diameter insect net at milk, soft, and
hard dough stages. Damaged grains were determinedvia the acid fuchsin staining technique (Litsinger et al.
1981).
2.6. Light trap collections
Pairs of kerosene metal light traps were used, made
by Laguna fishermen with the lamps enclosed in a
glass housing (Litsinger et al. 1979). Farmers were
trained to manage the light traps by depositing each
nights catch in vials of 70% alcohol. Trained staff did
the identification and counting with the aid of a
stereomicroscope. Light traps were placed two pervillage in rice fields out of sight from one another and
unobstructed by trees within a radius of 100 m.
Enough kerosene was used to enable the lamps to
burn throughout the night. The height of the flame
was standardized across sites by wick length. Collec-
tions in the four dryland rice sites were compared to
three rainfed wetland and three irrigated sites where
similar research teams worked. Two irrigated sites
were separated into areas that represented the
standard synchronized double-rice cropping and a
more intensive cropping (2.5 crops in 5 years) planted
asynchronously (Loevinsohn et al. 1988). Counts
were summed over six months that represented the
mean period of a seasonal rice crop. This was done so
that rainfed single crop areas could be compared to
irrigated double crop sites on a per crop basis. In
irrigated sites data were summarized for each wet and
dry season crop based on the planting pattern each
year. Data presented are averages of all of the crops
during the specified years for each species.
2.7. Statistical analysis
All statistical analyses were performed by SAS with
P 0.05 as the criterion for significance. Resultswere subjected to one-way ANOVA. Treatment
means were separated using the paired t-test for two
variables or the Least Significant Difference (LSD)
test for more than two variables. Means are shown
with standard errors of the mean (SEM) using a
pooled estimate of error variance.
3. Results3.1. Insect pests
3.1.1. Siniloan
The most injurious group of insects in the slash and
burn site were sown-seed and seedling pests which
reduced plant stand 91% in 1984 and 27% in 1985.
The first group included ants, dominated by the
ubiquitous Solenopsis geminata (F.), that removed
seeds, while field crickets fed on the germinating
seeds. Foliar pests attacking young seedlings were
seedling maggot Atherigona oryzae Malloch and a flea
beetle Chaetocnema basalis (Baly). The rice seedling
maggot caused 42% deadhearts in 1984 but rose to440% deadhearts in 1985 (Table 1). The 2-mm flea
beetle adults caused shot hole leaf damage to 46% of
young seedlings leading to death of many in 35 days.
Its normal hosts are grasses (Barrion and Litsinger
1986a).
As rice was planted in such small areas of burned-
off forest there were fewer species in this pest complex
compared to other sites. This was due to both the
small size of fields and lack of alternative hosts.
Absent were sown-seed and root pests, such as root
aphids, mole crickets, white grubs, mealybugs, and
termites. Foliar pests such as plant- and leafhoppers,stemborers, and defoliators were also missing.
The crop suffered periods of moisture stress
manifested by leaf rolling. These conditions encour-
aged a leaf-feeding thrips Stenchaetothrips biformis
(Bagnall) to multiply causing stippling by removing
photosynthetic area, but their numbers were soon
suppressed by heavy rains (Barrion and Litsinger
1986b). Two leaffolder species were encountered with
Marasmia exigua (Butler) being more prevalent than
Cnaphalocrocis medinalis (Guene e) as the former has
a wider host range (Barrion et al. 1991). Light trap
collections recorded leaffolders year-round and they
peaked during rice harvest in the lowlands 1520 km
away, showing their high migratory capability.
Damage was non-economic, however. Rice seed
bugs Leptocorisa oratorius (F.) and L. acuta (Thun-
berg) were recorded at relatively high densities (4.1/
m2). The latter is less associated with rice areas and
has a wider plant host range. This was the highest
density recorded among 11 research sites representing
dryland, rainfed, and irrigated wetland ecosystems
(Litsinger 2008).
Kerosene light trap collections showed low to
moderate densities of brown planthopper and green
leafhoppers along with one of their major predatorsCyrtorhinus lividipennis Reuter (Table 2). Yellow
stemborers were also caught in low levels. Despite
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Table1.Effectofincreasinginputlevelsofnutrients,soilamendments,andinsecticideonyieldofBenernaldrylandricegro
wninslashandburnculture,Siniloan,Lagunaprovince,
Philippines,1985.a
Treatment
T
reatmentinputs(dosageperhectare)
Plantstandd
(no.plants/30hills)
14DE
Leafbeetle
(%
damaged
leaves)14DEe
Seedlingmaggot
(%
deadhearts)
28DEe
Yield(t/ha)
f
Nutrients(kg/ha)
Soilamendments
Insecticidetreatment
1.High
input,
fullp
rotection
46N,28P,14K
500kglime
3tchicken
manure/ha
0.4kga.i.carbosulfan
ST/ha
weekly
foliarspraysc
206+
24ab
8.3+
4.9a
17.4+
4.5a
0.48+
0.25a
2.High
input,
foliarprotectiononly
46N,28P,14K
500kglime
3tchicken
manure/ha
Weeklyfoliars
praysc
142+
15c
7.8+
5.1a
42.4+
23.2c
0.47+
0.26a
3.Low
input,seed
treatmentonly
23N
Ash
b
0.25kga.i.carbosulfanST/ha
221+
26a
12.4+
8.6a
28.8+
11.3ab
0.42+
0.24a
4.Low
input,
noprotection
23N
Ash
b
162+
11c
38.9+
13.2b
30.6+
16.3b
0.45+
0.21a
5.Low
input,
seed
treatmentonly
Ash
b
0.25kga.i.carbosulfanST/ha
204+
27ab
13.5+
9.9a
18.9+
9.0a
0.20+
0.08b
6.Low
input,
seed
treatmentonly
0.25kga.i.carbosulfanST/ha
162+
16c
11.2+
7.2a
15.7+
5.4a
0.21+
0.07b
7.Untreated
149+
19c
45.7+
20.3b
37.0+
15.2b
0.06+
0.05c
P
500001
500001
500001
500001
F
5.32
4.84
5.92
4.98
df
10
10
10
10
aAverageoffourreplications.Inacolumn,means(+SEM)followedbyadifferentletterares
ignificantlydifferent(P
0.05)byLSDanalysis.DE
daysaftercropemergence.
b
cup
perdibbleholederivedfromforesttrees.
c0.75kg
aimonocrotophosEC/haweeklyduringt
hevegetativestagetopanicleinitationandduringripening,0.75kgaiBPMC
chlorpyrifos(BrodanEC)/hafrompanicleinitiationtoflowering.
ECem
ulsifiableconcentrate(liquid)formulation.ST
seedtreatment.
d30dibb
leholessampledperreplication.
e50hills
sampledperreplication.
f25-m
2
samplesperreplication
134 J.A. Litsinger et al.
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Table2.
Abundanceofinsectsandvariablesofricecroppingintensitybyricecultureasdeterminedfromkerosenelighttrapssetupin12locationsinthePhilippines,19791992.
Riceculturea
Town
Province
No.
crops/yr
Area
inrice
(%)b
Seasonaltotalperlighttrapperlocationc
Brown
planthopper
N.
lugens
Whitebacked
planthopper
S.
furcifera
Green
leafhoppers
Nep
hotettixspp.
Zigzag
leafhopper
R.
dorsalis
White
leafhopper
C.spectra
C.
lividipennis
miredpredator
Scirpophaga
sp
p.
Stem
borers
d
Other
stemborerse
Dryland
Siniloan
Laguna/Quezon
1.0
3
185+
78d
451+
144c
425+
158b
41+
7c
Claveria
MisamisOriental
1.0
9
262+
75d
130+
37b
75+
29c
190+73
c
37+
19b
45+
11c
178+
98c
Tupi
SouthCotab
ato
1.0
14
2,908+
864c
498+
115b
1,449+
398c
1,802+16
1b
80+
22b
1,780+
272b
170+
43c
315+
87bc
Tanauan
Batangas
1.0
20
130+
78d
1
,700+
367b
860+
452c
720+29
4c
50+
23c
Rainfedw
etland
Solano
Cagayan
1.0
60
491+
217d
1
,527+
527b
3,218+
2,320b
312+
103ab
595+
269b
437+
133c
131+
36c
Manaoag
Pangasinam
1.0
85
289+
94d
321+
81b
2,179+
538c
305+79
c
475+
66c
0c
Oton/Tigbauan
Lloilo
1.0
85
1,824+
528cd1
,012+
215b
2,440+
770c
1,016+61
2bc
458+
185a
455+
314b
997+
108b
38+
30c
Irrigated
(synchronous)
Victoria/
StaMaria
Laguna
1.9
90
214+
79d
1
,366+
896b
629+
426c
195+95
c
410+
168b
413+
88c
35+
35c
Cabanatuan/
Zaragoza
NuevaEcija
2.0
80
154+
14d
361+
77c
305+
17c
0c
Koronadal
SouthCotab
ato
2.0
70
1,677+
345cd
549+
152b
2,279+
617c
855+16
9c
93+
17b
706+
252b
662+
83bc
405+
46b
Irrigated
(asynchronous)
Jaen
NuevaEcija
2.0
80
15,224+
238a
9,207+
2,561a
137+
59c
0c
Koronadal
SouthCotab
ato
2.4
70
11,168+
1,849b4
,043+
1,117a
3,158+
501b
2,961+38
9a
145+
21ab
7,169+
720a
2,519+
430a
751+
123a
P
50.0001
50.0001
50.0001
50.0001
50.0001
50.0001
50.0001
50.0001
F
37.01
6.76
5.54
24.02
3.12
17.46
19.91
17.92
df
49
40
49
40
32
36
4
9
45
RiceCult
ureAverage
Dryland
871b
776b
709b
904b
59
1,103b
77
b
247
Rainfedw
etland
868b
953b
2,612ab
661b
385
525b
636
ab
56
Irrigated
(synchronous)
682b
957b
650b
551b
93
558b
460
ab
147
Irrigated
(asynchronous)
13,196a
4,043a
6,183a
2,961a
145
7,169a
1,32
8a
376
P
50.0001
0.04
0.02
0.02
0.12ns
0.007
0.04
0.07ns
F
40.95
6.15
6.30
12.09
7.33
37.03
3.04
0.76
df
11
8
11
7
5
6
1
1
9
aSynchronyreferstofarmersplantingdatesandsy
nchronyoccurswhenfarmersplantwithinaperiodofonemonth,theaveragegenerationalperiodofmostinsectpests(Loevinso
hnetal.1988).
bCircum
ferenceof1km
2
centeredaroundeachlighttrap.
cDailycountsfromkerosenelighttraps.Nodatain
dicatesthattheinsectinquestionwasnotmeasured.
Inacolumn,means(+SEM).followedbyadiffere
ntletteraresignificantlydifferent(P4
0.05)byLSDanalysis.
dS.innot
ata.S.incertulas.
eChilosu
ppressalis,Sesamiainferens,Maliarphasp.
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these catches that were equivalent to a number of
wetland sites where moderate damage levels occur on
almost each crop, such densities did not translate into
significant infestations in the slash and burn area, as
deadhearts or whiteheads were rarely encountered.
3.1.2. Claveria
Stand loss averaged 14% in the vegetative stage, more
from sown-seed and root pests (Table 3), mainly ants
again dominated by S. geminata. Germinating seed
pests were mole cricket Gryllotalpa orientalis Burme-
ister and field crickets, while root pests were white
grubs, termites, root aphids, and mealybugs. The
subterranean termite Macrotermes gilvus (Hagen)
prefers wheat to rice as a 100-m2 trial plot (var.
Trigo) sown within a rice field was totally denuded in
the seedling stage. Densities in rice reached 7 termites/
50 plants with minimal damage to rice.The seedling maggot averaged a modest 6%
deadhearts. After tillering their numbers declined, as
the larvae can only attack developing tillers. Defolia-
tion from general defoliators including C. basalis flea
beetle was subeconomic. The most common defolia-
tors were leaffolders that averaged only 1% damaged
leaves, the most common being M. patnalis Bradley
followed by M. exigua and C. medinalis. Also noted
was the armyworm Mythimna separata (Walker)
which did negligible damage.
Three species of root aphids built up in numbers
with crop growth reaching 1.8/plant. Tetraneuranigriabdominalis (Sasaki) was most common followed
by Geoica lucifuga (Zehntner) and Rhopalosiphum
rufiabdominalis (Sasaki) in fields where numbers were
high, plants turned yellow and became stunted. The
common root mealybugs were Trionymus sp. and
Pseudococcus sp. where only token numbers occurred
(1/50 plants).
Stemborer damage as deadhearts or whiteheads
was 51% where species composition determined by
tiller dissection showed striped stemborer Chilo
suppressalis (Walker) to be the most dominant (72%
of collections) followed by yellow stemborer (11%),
white stemborer S. innotata (Walker) (10%) and
finally pink stemborer Sesamia inferens (Walker)
(6%). Larvae were reared to distinguish between the
Scirpophaga species. Rice seed bugs were a mixture of
L. oratorius and L. acuta averaging 1/m2.
White grubs also fed on roots having the greatest
detrimental effect on seedlings averaging 8/10-m row
after harvest. The two most common species Leuco-
pholis irrorata (Chevrolat) and Holotrichia mind-
anaoana Brenske had synchronized 2-year life-cycles
which on odd-numbered years resulted in the last
instar larvae being in the field at the time of crop
planting (Litsinger et al. 2002). Females ovipositduring land preparation predominantly in even
numbered years when only the less damaging young Table3.
Insectpestdensitiesonfarmersdryland
ricefieldssowntoUPLRi5inClaveria,MisamisOrientalandTupi,SouthCotabato,
Mindanao,Philippines19841990.a
Site
Crops
(no.)
Years
Plantstandreduction(%)21DEb
Seedingmaggot
(%
deadhearts)
21DEb
No.per50plants40DEd
Stemborer(%)b
Leaffolder
(%
damaged
flagleaves)b
Riceb
ug
(no./m
2)e
Whitegrubs
(no./10-mrow)
atharvest
f
Sown
seedpests
Root
pests
Combinedc
Ter
mites
Root
aphids
Rootmealy
bugs
Deadhe
arts
5070DE
Whiteheads
Claveria
7
198490
11.0+
2.3
9.3+
1.6
14.3+
1.9
5.8+
1.1
7.3+
2.9
88+
30
1.0+
0.6
0.6+
0.3
0.5+
0.2
1.2+
0.3
1.0+
2.1
8.4+
2.8
Tupi
4
198687
198990
8.4+
3.9
8.5+
3.8
13.6+
2.8
8.3+
2.0
9.9+
5.4
172+
33
0
0.5+
0.3
0.7+
0.3
6.5+
2.8
1.0+
0.9
7.2+
5.6
aEachyear48fields(replications)weremonitored
frominsecticideuntreated100m
2
plots.DE
daysaftercropemergence.Dataarem
eans+
SEM.
b0-mrowsample.
cSampledfromtheuntreatedcheck.
dPlantsdugupto10cmdepthandrootsinsepected
.
eDataar
emeansfromsampling25m
2
duringmilk,soft,andharddoughstages.
fPlantsd
ugupandsoilinspectedto20cmdepth.
136 J.A. Litsinger et al.
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larvae affect the crop. Three other species were also
found feeding on rice but in much lower densities:
H. flachi Brenske, Adoretus luridus Blanchard, and
Anomala humeralis Burmeister.
Claveria had the lowest light trap collections of
any of the sites (Table 2), as it was the most isolatedfrom wetland areas. Plant-/leafhoppers were rarely
encountered on the crop. As with Siniloan, stemborer
species balance favoured genera other than
Scirpophaga.
3.1.3. Tupi
An average stand reduction of 14% resulted from
both sown-seed and root pests in this favourable
dryland site (Table 3). The main seed pest was S.
geminata, along with mole and field crickets. Seedling
maggot damage averaged 8% deadhearts but other-
wise the seedling stage was not significantly infestedby insect pests, as flea beetle damage was barely
noticed. Root pests were white grubs and termites.
White grubs continued to gnaw away on roots
throughout the crop season; the same five species as
found in Claveria were recorded. They averaged 7 per
10-m row at harvest. Termites averaged only 1 per
five plants. Other root feeding pests were root aphids
which averaged 43 per plant and thus were one of
the most important pest guilds. Root mealybugs,
however, were not recorded.
Stemborers were mainly Scirpophaga dominated
by white stemborer although there was a species shiftin the province prior to the study due to El Nino
climate change (Litsinger et al. 2006a). Damage
levels, however, were extremely low with deadhearts
and whiteheads 51%. Leaffolders averaged 7%
damaged leaves dominated by M. patnalis (55% of
field collections) and C. medinalis (45%). Rice seed
bugs were low in number (1/m2).
Light trap densities of the major rice pests were
greatest in Tupi among the dryland rice sites and even
greater than many other wetland rice sites (Table 2).
The exception was whitebacked planthopper Soga-
tella furcifera (Horvath) which was more abundant in
Tanauan due to its close proximity to Laguna
wetland areas. Densities of brown planthopper,
zigzag leafhopper Recilia dorsalis (Motschulsky),
and Cyrtorhinus mirid were highest in Tupi except
for one or two of the asynchronously planted
irrigated rice sites. Green leafhopper numbers were
high in the dryland sites but lower than the irrigated
wetland sites. Stemborer densities were also highest
among the dryland sites but much less than at the
wetland sites. The ratio of Scirpophaga to non-
Scirpophaga stemborers favoured the latter, equal to
the other dryland sites. The most abundant was
Maliarpha sp. with 63% of the catch followedby S. innotata (26%), C. suppressalis (9%), and
S. inferens (2%).
3.1.4. Tanauan
Insect pest species richness and their densities in
Tanauan were only higher than in Siniloan. Sown-
seed and root pests (white grubs and termites) each
reduced stand 911 and 1110%, respectively, whenmeasured individually and for each varietal type
(Table 4). When both contributions are combined,
stand reduction ranged from 14 to 16% for Dagge
and UPLRi5, respectively. S. geminata was probably
responsible for most of the loss of seed followed by
mole and field crickets. Only one species of white
grub L. irrorata was encountered and is a major pest
of sugarcane in nearby fields. Farmers cite termites
dominated by M. gilvus along with Coptotermes spp.
as major dryland rice pests. Termites are permanent
residents of the uplands as their nests extend below
the plough pan and feed mainly on maize stalks and
rice straw. Farmers, however, overestimate theimportance of termites but do not sufficiently value
the other pests. Seedling maggot was also present but
at very low numbers during the vegetative stage.
Several defoliating Lepidoptera were recorded,
based on periodic field collections during the 1976
1980 seasons mainly in the reproductive stage. From
the total collection of 635 larvae and pupae, the most
abundant was greenhorned caterpillar Melanitis leda
ismene Cramer (46% of the total) followed by
armyworms M. separata (17%) and Spodoptera
mauritia acronyctoides Guenee (16%) plus rice
skipper Pelopidas mathias (F.) (13%) and brownsemi-looper Mocis frugalis (F.) (9%). However, the
amount of defoliation from these species never
reached economic levels.
The light trap catches showed that among the four
dryland sites Tanauan had supported high levels of
plant- and leafhoppers, second only to Tupi (Table 2).
The highest light trap densities were of whitebacked
planthopper followed by green and zigzag leafhop-
pers which were mirrored in field sampling (Figure 1).
Densities peaked in the late reproductive stage and
declined toward crop senescence with the abundance
of Cyrtorhinus predator trailing that of its prey.
Abundance of yellow stemborer from light trap
catches was equivalent to that at other dryland sites
except Tupi. Cyrtorhinus numbers were also moderate
despite its major prey (planthoppers) being abundant
on the crop.
Plant- and leafhoppers were more abundant on
Dagge than on UPLRi5 (Table 4). Numbers were
higher on the traditional variety than on the modern
variety, and at times small patches of hopperburn
were noticed in some fields. Of the green leafhoppers,
most individuals (83%) were N. virescens, as the
remainder being N. nigropictus (Sta l) indicating that
the site was still within the dispersal range of riceinsect pests moving from wetland areas. Cyrtorhinus
predators were also prevalent, their numbers building
International Journal of Pest Management 137
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up over the season and peaking after the planthop-
pers (Figure 1). Spider densities were at 12/m2
throughout the crop season. The most common
spiders were Argiope catenulata (Doleschall) (Aranei-
dae), Clubiona japonicola Boesenberg et Strand
(Clubionidae), Pardosa pseudoannulata (Boesenberget Strand) (Lycosidae), Tetragnatha javana (Thorell),
T. mandibulata Walckenaer, and T. nitens (Audouin)
(Tetragnathidae).
Three species of rice stemborer were recovered by
periodic stem dissections (n 703 larvae) with
S. incertulas the most abundant (74%) followed by
S. inferens (19%) and dark headed stemborer
C. polychrysus (Meyrick) (7%). The combined da-
mage as deadhearts was minimal 52%, with white-
heads only slightly 43% (Table 4). Damage was
higher on Dagge probably because as it was the taller
variety it elongated more, making it more susceptible
(Bandong and Litsinger 2005). These levels were alsosubeconomic. S. innotata does not occur on Luzon.
The high nitrogen usage encouraged three leaf-
folders, M. patnalis being the most commonly
encountered while M. exigua colonized first followed
by C. medinalis. Damage was greatest at the flag leaf
stage, averaging 17 and 10% damaged leaves on
traditional and modern varieties, respectively. Few
living larvae were found upon opening up folded
leaves indicating high rates of predation. Rice seed
bug numbers were moderate averaging 1/m2 over the
ripening stage which damaged 57% of rice grains.
3.1.5. Comparison of rice agro-ecosystems
Kerosene light traps operated over standardized crop
seasons in 12 sites measured the activity of a narrow
spectrum of rice insect pests, mainly plant-/leafhop-
pers, stemborers, and Cyrtorhinus mirid that preys on
hoppers. The overall analysis shows that brown
planthoppers were just as prevalent in dryland as in
other synchronously planted wetland sites (Table 2).
The same was true of whitebacked planthopper for
which there are no resistant rice varieties. Brown
planthopper was found at low levels in three of the
four dryland sites despite susceptible varieties being
grown. At Tupi the incidence was as high as in
irrigated areas and only less in the two asynchro-
nously planted irrigated areas where genetic resis-
tance had broken down. The low levels in Manaoag
(IR36), Victoria (IR42) and Cabatanuan/Zaragoza
(IR42, IR52) indicate that the rice varieties planted at
the time were resistant to brown planthopper. At
Iloilo farmers grew a mixture of traditional types and
IR36 which was resistant. Tupi farmers selected
modern semi-dwarfs that, however, were not
resistant.
Green leafhoppers were most abundant in Tupiwith the lowest incidence in Claveria but in none of
the dryland sites were varieties resistant to greenTable4.
Insectpestdensitiesonfarmersdryland
ricefieldssowntotraditionalandmodernricevarietiesinTanauan,Batangas19761980.a
Plantstand(%
reduction)21DEb
No.per25m
2
40DEd
Stemborers
b
Ricebug
de
Variety
Crops
(no.)
Sown
seedpests
Root
pests
Combinedc
Nep
hotettix
spp.
N.
lugens
S.
furcifera
R.
dorsalis
C.spectra
Cyrtorhinus
predator
Deadhearts(%
)
Whiteheads
Leaffolder
(%
damaged
flagleaves)b
No./m
2
Damaged
grains(%)
Whitegrubs
(no./10-mrow)
atharvest
f
50DE
70DE
Dagge
5
9.1+
1.411.4+
2.214.1+
4.7
78+
47
143+
90
1,318+
763
158+
141
8.1+
2.531.4+
10.10.4+
1.41.6+
0.5
2.6+
0.8
17.3+
5.1
1.3+
1.6
4.1
+
0.6
1.2+
0.9
UPLRi5
3
10.7+
3.0
9.8+
2.416.4+
5.3
34+
8
34+
12
310+
218
27+
17
7.3+
1.723.2+
2.2
0.3+
0.10.5+
0.2
1.5+
0.6
9.6+
4.0
1.3+
0.9
3.7
+
0.5
1.7+
1.5
aEachyear48field(replications)weremonitoredfrominsecticideuntreated100m
2
plotsfor
eachvariety.
DEdaysaftercropemergence.Dataaremeans+
SEM.
b10-mro
wsample.
cSampledfromtheuntreatedcheck.
dSampledbyD-VAC1
suctionmachine.
eDataar
emeansfromsamplingduringmilk,soft,a
ndharddoughstages.Damagedgrainswe
redeterminedbytheacidfuchsinstainingtechniqueofthefeedingsheaths(Litsingeretal.1981).
fPlantsd
ugupandsoilinspectedto20cmdepth.
138 J.A. Litsinger et al.
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leafhopper grown. In the case of dryland sites, crop
apparency was low due to a long dry fallow and in
irrigated sites genetic resistance prevailed. Modern
rices are resistant to green leafhoppers, as can be seen
in Laguna and Cabanatuan/Zaragoza among the
irrigated sites. However, resistance had broken down
in the asynchronous areas. Generally the lowest
incidence was in both dryland and irrigated synchro-
nous sites with high numbers in rainfed wetland and
asynchronous irrigated areas. The short season dry-
land rice environment suppressed green leafhopper
build up whereas in synchronous irrigated sitesresistant varieties were responsible. There are no
resistant varieties for zigzag leafhopper and white
leafhopper Cofana spectra (Distant). The highest
zigzag leafhopper incidence was the asynchronous
sites, but was also recorded in Tupi, and there were
no differences between dryland, rainfed wetland, and
irrigated (synchronous) cultures. Also, there was no
significant difference between rice cultures for white
leafhopper. The mirid predator densities mirrored
more the brown planthopper than any other prey
species.
The lowest incidence of Scirpophaga stemborers
was recorded in the dryland habitat, whereas the
highest catches were recorded in Koronadal fromwhite stemborer in the asynchronous area. The ratio
of non-Scirpophaga to Scirpophaga was positive only
Figure 1. Abundance of planthoppers, leafhoppers, spiders, and a mirid predator on a traditional dryland rice varietydetermined by weekly suction sampling with a DVAC machine in Tanauan, Batangas, Philippines, 1980. Data are averages of25 m2 samples in each of four fields where rice was sown in June and harvested in October. WBPH, whitebacked planthopperSogatella furcifera; BPH, brown planthopper Nilaparvata lugens; GLH, Nephotettix spp. green leafhoppers; ZLH, zigzagleafhopper Recilia dorsalis, and the mirid predator Cyrtorhinus lividipennis.
International Journal of Pest Management 139
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in the dryland sites. Differences among habitats for
non-Scirpophaga species were not significant. Skew-
ing the results were three sites wherein only Scirpo-
phaga stemborers were found. Koronadal had high
incidence of Maliarpha sp. stemborers in both
dryland and irrigated sites.
3.2. Yield loss
3.2.1. Siniloan
The slash and burn crop suffered greatly from both
biotic and abiotic stresses, foremost of which was the
eroded acidic soil which reduced root growth, thus
when periodic water stress occurred the plants were
not able to extract moisture from deep in the soil.
Biotic stresses were mainly diseases and vertebrate
and insect pests to the extent that in 1984 there was
no grain harvest. Most serious was leaf and neck blast
disease (Pyricularia oryzae Cav.) followed by rats andbirds and an array of insect pests. Also, those plots
that grew best from added soil amendments and good
insect control suffered greater yield loss than the
poorer-growing ones due to lodging from typhoons.
At harvest, plant height and biomass were insignif-
icantly different between treatments. Less blast
occurred in the second year which produced a grain
harvest that illustrates how complex quantification of
yield loss is when multiple stresses are involved. The
farmers practice was the untreated (treatment 7)
which yielded 60 kg/ha, barely returning the seed
sown (Table 1). If insecticide seed treatment isprovided, a yield of 210 kg/ha occurred resulting in
a loss of 0.15 t/ha or 71% (treatment 6 vs. 7) from
sown-seed and seedling pests. However, if the farmer
follows the recommended practice of adding 23 kg N/
ha there is no yield loss from insect pests (treatment 3
vs. 4) because of crop compensation. The best
treatment yielded 480 kg/ha, that is the technical
yield potential, which was also reached by applying
only 23 kg N/ha plus ash without insecticide. There
was no additional yield benefit from foliar sprays,
thus the measured yield loss from insects came from
control of the sown-seed and seedling pest guilds.
Clearly, the degree of loss is highly influenced by
agronomic practices.
3.2.2. Claveria
Claveria resulted in an average loss of 0.79 t/ha or
23% as the difference between the fully protected
crop (3.43 t/ha) and the untreated (2.64 t/ha) grown
under farmer management (Table 5). Using the
partitioned yield loss method, losses (t/ha) were
highest from white grubs and termites (0.31) followed
by root aphids (0.21), sown-seed/seedling pests (0.16),
rice seed bugs (0.09), and stemborers (0.03). The totalyield loss equalled 22.8%: that breaks down to 8.3%
for white grubs and termites, 6.6% for root aphids, Table5
.Yieldlossdeterminedbypartitionedgrowthstage,insectpestguildinse
cticidecheckmethodinfarmersfieldsinClaveria,MisamisOrientalandT
upi,S.Cotabato,
Philippines19851991.a
Site
Crops
Years
Yield(t/ha)
Yieldloss(t/ha)
Yieldloss(%
)
Complete
protection
Untreated
Total
Whitegrubs
termites
Seed/
seedling
p
ests
Rootaphid
Stemborer
leaffolder
Ricebug
Total
White
grubs/
termites
Seed/
seeding
pests
Root
aphid
Stemborer/
leaffolder
Ricebug
Claveria
7
198591
3.43+
0.21a
2.64+
0.16b
0.79+
0.24
0.31+
0.18a
0.16+
0.21ab
0.21+
0.17ab
0.03+
0.10b
0.09+
0.08ab
22.8
8.3
5.0
6.6
0.7
2.2
P
0.01
0.04
F
6.36
3.17
df
73
73
Tupi
4
1987198991
3.46+
0.19
2.96+
0.32
0.50+
0.16
0.10+
0.08
0.11+
0.08
0.19+
0.15
0.09+
0.07
0.01+
0.04
15.0
3.3
3.5
5.5
2.5
0.2
P
0.21ns
ns
F
1.61
0.57
df
39
39
aYieldlo
sswasdeterminedasthedifferencebetweenafullprotectiontreatmentthatprotectedfivegrowthstagesandassociatedpestgu
ildswithinsecticidesselectedfortheireffic
acyandphytotoxic/
phytotonicneutrality
Fivetreatmentssucessivelyomittedinsecticideprotectionsothatlossescouldbeattributedtothatgrowthstage/guild
Seetext
fordescriptionsofinsecticides,dosagesandtiming.Alltrialswereconductedinfarme
rsfieldswitheachfieldasareplication.
Means+
SEM
inarownotfollowedbyacommonletteraresignificantlydifferent(P
0.05)byLSDtest,ns
notsignificantlydifferent
140 J.A. Litsinger et al.
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5.0% for sown-seed pests, 2.2% for rice seed bugs,
and 0.7% for stemborers.
3.2.3. Tupi
Interestingly the yield potential in Tupi was similar tothat in Claveria despite these being better soils in
Tupi. The four crops in Tupi recorded a 0.50 t/ha or
15% loss as the difference between 3.46 and 2.96 t/ha
for full protection and the check (Table 5). Yield loss
was lower than in Claveria, even though pest
complexes and densities were similar. The ranking
of yield loss differed, in that the greatest loss was from
root aphids (0.19 t/ha or 5.5%), sown-seed/seedling
pests (0.11 t/ha or 3.5%), white grubs and termites
(0.10 t/ha or 3.5%), stemborers (0.09 t/ha or 2.5%),
and rice seed bugs (0.01 t/ha or 0.2%).
3.2.4. Tanauan
In Tanauan the modern variety out-yielded the
traditional variety under the same management in
both the comparison of full protection (4.01 vs.
2.90 t/ha) and untreated (3.61 vs. 2.85 t/ha) (Table 6).
With Dagge there was an insignificant difference
between the protected (2.90 t/ha) and the unprotected
check (2.85 t/ha); total loss was too low (5%) for us
to have confidence in assigning significance appor-
tioned across each pest guild. There was, however, a
significant yield loss in UPLRi5 of 0.40 t/ha or 18%
between protected and unprotected treatments. Thishigher loss was spread fairly evenly between guilds
with most due to white grubs/termites and sown-seed/
seedling pests (5.9% each), and least in the ripening
stage (2.3%). The 4.1% loss in the reproductive stage
was probably from whitebacked planthopper.
3.3. Crop management
3.3.1. Siniloan
The slash and burn crop was protected with a seed
treatment as an initial recommended practice which
was tested together with several agronomic and
insecticide interventions including organic and inor-
ganic fertiliser amendments and foliar sprays. With
carbosulfan seed treatment, yields increased signifi-
cantly from 60 to 210 kg/ha, giving a marginal return
of only $0.60/ha (Table 1). The highest yield with the
least amount of inputs was obtained from applying
23 kg N/ha and ash to reach 450 kg/ha and a
marginal return of $42 and B:C ratio was a highly
favourable 6.1. Adding the seed treatment did not
increase yield, neither did adding lime, chicken
manure, doubling the N rate from 23 to 46 kg/ha,
or foliar insecticide sprays. This agronomic recom-
mendation probably increased the crops compensa-tory ability against insect pest damage, but it may
change if and when the yield potential can be Table6
.Yieldlossdeterminedbypartitionedgrowthstage/pestguildinsecticidecheckmethodinfarmersfieldsinTana
uan,Batangas,Philippines,19761980
.a
Varietytype
Crops
Years
Yield(t/ha)
Yieldloss(t/ha)
Yieldloss(%)
Complete
protection
Untreated
Totalyield
loss
Whitegrubs/
termites
Sownseed/
seedlingpests
Reproductive
stage
Ripening
stage
Total
yieldloss
White
grubs/
termites
Seed/
seedling
pests
Reproductive
s
tage
Ripening
stage
Traditional/
Dagge
5
197680
2.90+
0.082
.85+
0.06
0.05+
0.07
0.02+
0.02
0.01+
0.02
0.01+
0.01
0.01+
0.02
1.7
0.8
0.3
0.3
0.3
P
0.734ns
F
0.117
df
63
Modern/
UPLR
i5
3
197880
4.01+
0.163
.61+
0.35
0.40+
0.38
0.13+
0.12
0.13+
0.12
0.09+
0.10
0.05+
0.06
18.2
5.9
5.9
4.1
2.3
P
0.165ns
F
2.02
df
35
aYieldlo
sswasdeterminedasthedifferencebetweenafullprotectiontreatmentthatprotected
fourgrowthstagesandassociatedpestguildswithinsecticidesselectedfortheirefficacy.
Fourtre
atmentssuccessivelyomittedinsecticidepro
tectionsothatlossescouldbeattributedtothatgrowthstage/guild.
Seetext
fordescriptionsofinsecticides,dosagesandtiming.Alltrialswereconductedinfarme
rsfieldswitheachfieldasareplication.
Means+
SEM
inarowfollowedbyadifferentletteraresignificantlydifferent(P5
0.05)by
LSDtest,ns
notsignificantlydifferent
International Journal of Pest Management 141
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significantly raised, i.e. with a blast resistant variety,
better soil management, or improved vertebrate pest
control.
3.3.2. Claveria
The crop management variables tested were inorganic
fertiliser, seeding rate, as well as insecticide soil and/
or seed/seedling treatments. The lowest yields resulted
without addition of either fertiliser or insecticide
producing equally low levels (2.4 t/ha) at both the 50
and 90 kg/ha seeding rates (Table 7). The minimal
input to raise the yield significantly above the
untreated level was the adding of inorganic fertiliser
(50-25-0) at the 90 kg seed/ha rate producing 2.6 t/ha
but a negative marginal return of $9/ha. The next
yield plateau was reached at a seeding rate of 50 kg/
ha, 50-25-0 fertiliser level, and an insecticide seed
treatment which improved to 2.8 t/ha, but only ameagre marginal return of $7/ha with a B:C ratio of
only 1.2. The addition of a soil insecticide treatment
to this last practice did not further improve yield. The
fully protected plots produced the highest yields
(3.4 t/ha) among all treatment combinations and
out-yielded the fertilised control at the same seeding
rate by 0.80 t/ha. This treatment was not a potential
practice; but it merely showed that there was more
scope for improvement. Thus the most profitable
practice for the farmer was to not apply any
agricultural inputs due to the meagre yield response
of added N and P.
3.3.3. Tupi
Almost the same mix of management practices was
tested in Tupi as in Claveria. Lowest yields again
were in the unfertilised and non-insecticide treated
plots at either 50 and 90 kg/ha seeding rates (2.42.5 t/ha) (Table 7). There was no benefit of
increasing just the seeding rate from 50 to 90 kg/
ha without fertiliser or seed treatment. The most
economical return was at 50 kg seed/ha with
inorganic fertiliser (50-25-0) and insecticide seed
treatment with highest marginal return of $90/ha
and 3.0 B:C ratio. Adding only fertiliser had a
greater benefit as yields increased 0.53 and 0.66 t/ha
in the 50 and 90 kg/ha seeding rates, respectively,
although not significantly. Economically there was a
marginal return of $44/ha and B:C ratio of 2.8
from use of inorganic fertiliser at 50 kg seed/ha
without seed treatment. If the farmer increased to90 kg seed/ha with fertiliser but without seed
treatment, the marginal return became $64/ha and
B:C ratio rose to a more favourable 3.1. Profit was
higher with an insecticide seed treatment however.
No further benefit was realized from applying the
more expensive soil insecticide treatments, indicat-
ing less pest pressure than in Claveria. In Tupi the
full protection treatment did not yield more than
the seed treatment or use of fertiliser. Therefore
there was no significant benefit from any insecticide
protection on a well fertilised crop at 90 kg seed/ha,
again indicating crop compensation.
Table 7. Yield response to crop management practices on dryland rice production, Claveria and Tupi, Mindanao,Philippines, 19841990.
Insecticidetreatment
Seedingrate
(kg/ha)N-P
(kg/ha)
Yield (t/ha)a
Claveria No. crops N Tupi No. crops n
Completeprotectionb
90 5025 3.41 + 0.23 a 7 28 3.61 + 0.22 a 4 16
Seed/seedling soil treatments
90 5025 2.89 + 0.15 b 4 16
Seed/seedling
treatment
90 5025 2.85 + 0.23 b 6 24 3.20 + 0.26 ab 4 16
Seed/seedlingtreatment
50 5025 2.84 + 0.28 b 3 28 3.48 + 0.24 ab 3 12
Soil treatment 90 5025 2.65 + 0.17 bc 2 8 3.41 + 0.29 ab 2 8Soil treatment 50 5025 2.69 + 0.39 bc 3 26 3.37 + 0.37 ab 3 12Untreated 90 5025 2.61 + 0.18 bc 7 28 3.17 + 0.28 ab 4 16Untreated 50 5025 2.33 + 0.25 c 3 28 2.96 + 0.32 ab 3 12Untreated 90 0 2.44 + 0.32 3 12 2.51 + 0.30 b 3 12Untreated 50 0 2.42 + 0.28 c 3 12 2.43 + 0.27 b 3 12P 0.007 0.03F 5.50 2.22df 294 135
aEach crop consisted of 46 farms replications (n) and treatments were analyzed on the basis of fields and not crops.
In a column, means + SEM followed by a different letter are significantly different (P 0.05) by LSD analysis.
Soil treatment was 0.25 kg al/Lindane G/ha, seed treatment was 0.30 kg ai carbosulfan ST/ha.
Fertilizer applied was 50250 with the N application split at 1425 days after crop emergence during inter-row cultivation and panicleinitiation while P was applied basally during land preparation.bFrom the yield loss trial which treatments were randomly mixed with the insect control treatments each season.
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3.3.4. Tanauan
Combinations of seeding rates and insecticide treat-
ment of seeds and soil were tested in one season with
Dagge variety. There was a yield benefit (0.50 t/ha) of
increasing the seeding rate from 50 to 100 kg/haalthough not significantly (Table 8), but it had a
highly favourable marginal return of $55/ha and a
B:C ratio of 8.3. Higher seeding rates up to 150 kg/ha
did not increase yield. At the 50 kg/ha seeding rate,
insecticide seed treatment resulted in modest but
insignificant yield gains (0.230.27 t/ha) that pro-
duced a marginal return of only $15/ha and B:C ratio
of 1.7. Slightly higher, but again insignificant, gains
(0.36 t/ha) were obtained with the 0.5 kg a.i. carbo-
furan/ha soil insecticide treatment at 50 kg seed/ha
producing a marginal return of $20/ha and B:C ratio
of 1.8. The highest yield gain (0.64 t/ha) was obtained
with the highest rate of soil insecticide treatment(2 kg a.i. carbofuran/ha) at the 100 kg/ha seeding
rate producing marginal return of only $7/ha and B:C
ratio of 1.1.
In 2 years trials (19801981) the same seed and
soil treatments produced no significant yield gain in
UPLRi5. In the 1979 trial which had more sown-seed
and root (white grub) pest pressure, also at 100 kg
seed/ha, that included both a seed treatment of
0.30 kg a.i. carbosulfan ST/ha (3.68 t/ha) and a soil
treatment of 0.75 kg a.i. diazinon G/ha (3.82 t/ha)
resulted in significant yield increase over the un-
treated of 3.28 t/ha (P 0.03, F 3.54, df 28).
Both insecticide treatments produced similar margin-
al returns of $31 and $41/ha, respectively, and B:C
ratios of 2.6 and 2.4. The average in untreated plotswith UPLRi5 over the 3 years was 3.6 t/ha; thus, in
1979 there was greater insect pest pressure. The
farmer practice of 100 kg seed/ha without insecticide
is probably the most economical practice as farmers
are hesitant to use insecticides.
4. Discussion
4.1. Yield potential
Except for the very low productivity of the slash and
burn site, yields in the unprotected treatment of the
other three sites ranged from 2.6 to 3.6 t/ha; these are
much higher than the world average of 1 t/ha. Thiseffect is likely attributable to the Philippine climate
and soils being as a whole more suitable for dryland
rice compared to those of many other countries. The
highest yielding site was Tanauan with the most
favourable soils, good crop management, and highest
use of inorganic fertiliser where the low tillering
variety Dagge averaged 2.9 t/ha, which is equal to
yields obtained from similar traditional varieties in
the irrigated wetlands. The high tillering UPLRi5
Table 8. Comparison of different practices on the yield of Dagge rice including increasing the seeding rate, insecticide seedand soil treatment and combinations thereof, Tanauan, Batangas, Philippines, 1976.a
Seed rate
Insecticide treatedPlant stand
b
no./m-row) 14 DEYield
c
(t/ha)Seed Soil
Seeding rate50 kg seed Untreated Untreated 35 d 2.00 b100 kg seed Untreated Untreated 45 bc 2.49 ab125 kg seed Untreated Untreated 60 a 2.43 ab150 kg seed Untreated Untreated 59 a 2.23 ab
Seed treatment50 kg seed Carbofuran ST Untreated 38 cd 2.27 ab50 kg seed Dieldrin WP Untreated 41 cd 2.23 ab
Soil treatment50 kg seed Untreated 0.5 kg ai carbofuran G/ha 38 cd 2.36 ab50 kg seed Untreated 2 kg ai carbofuran G/ha 41 cd 2.47 ab
Seed treatment increasing seeding rate100 kg seed Carbofuran ST Untreated 51 ab 2.27 ab100 kg seed Dieldrin WP Untreated 52 ab 2.19 ab
Seed treatment increasing seeding rate100 kg seed Untreated 0.5 kg ai carbofuran G/ha 52 ab 2.51 ab100 kg seed Untreateed 2 kg ai carbofuran G/ha 51 ab 2.64 aP 0.02 0.04F 5.38 4.98df 33 33
aFarmer practice was 00 kg seed/ha without insecticide usage and N was applied at 60 kg/ha in all treatments.
ST seed treatment formulation, WP wettable powder, G granule.
In a column, means + SEM followed by a different letter are significantly different (P 0.05) by LSD analysis. The randomized completeblock trial was replicated across six farmers fields.b20 samples of 1-m rows. DE days after crop emergence.cTwo 10 m2 yield cuts.
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averaged even more 3.6 t/ha under the same
management. Its characteristics of high tillering
combined with blast resistance make UPLRi5 an
attractive variety for dryland rice farmers. Tupi
soils are similar to those of Tanauan, but farmers
applied less nitrogen, 30 vs. 110 kg/ha, andaveraged 3.0 t/ha with UPLRi5 almost equal to
Dagge under higher N rates. The two sites with the
least favourable soils achieved the lowest yields.
Claveria, with its highly eroded acidic soils and low
organic matter content, averaged 2.6 t/ha. Slash
and burn culture, exemplified by Siniloan, recorded
the lowest yields with the farmers only doubling
their investment in seed.
4.2. Partitioned-growth-stage yield loss
There was no partitioned yield loss data for the slash
and burn site due to the difficulty of carrying outmultiple-treatment trials on small and very patchy
fields. The mean yield loss figure across the other
three sites for UPLRi5 was 18.6%, with 5.8%
attributed to white grubs and termites, 4.8% to
sown-seed/seedling pests (ants, crickets, seedling
maggot, and flea beetles), 4.0% to root aphids and
mealybugs, 2.4% to reproductive stage pests (stem-
borers, leaffolders and plant- and leafhoppers), and
1.6% to rice seed bugs.
The partitioned-growth-stage method has its
limitations. We noted interactions in the yield loss
calculations between pest guilds attributed to thebroad spectrum nature of the insecticides used and
the overlapping growth stages of a number of them.
The greatest interaction was evident with Lindane
granules between damage caused by white grubs and
termites (root pests) that would also have affected
sown-seed pests such as ants and crickets. The degree
with which this occurred can be seen in Tables 3 and 4
where sampling plant stand in the untreated controls
(combined) was 3.36.0% lower loss than was
estimated by separate treatments that measured
sown-seed/seedling and root pest protection. Other
overlapping stages were between root aphids/mealy-
bugs and the foliar pest protection for the reproduc-
tive stage. In the former the granular insecticide
carbofuran directed at root aphids and mealybugs
would have had some systemic activity against
stemborers and leaffolders dwelling in and feeding
on the above-ground plant parts. The dosage selected
(0.75 kg ai/ha) for carbofuran was such that only
trace amounts would have been taken up by the stems
and leaves from the root zone placement. Any
statistical interaction would have underestimated
loss from reproductive pests.
Additional interactions would have developed
from use of carbofuran as it has other propertiesthan as an insecticide. In addition to being a
nematicide it also has been found to have plant
growth hormone like properties (Venugopal and
Litsinger (1984). Nematodes are a serious problem
in dryland rice (Villanueva et al. 1992), causing
high losses in their own right. In fact, carbofuran is
the chemical of choice for estimating losses in the
nematicide check method, but again the dosageused in our study (1 kg ai/ha) was half used by
nematologists (e.g. Plowright et al. 1990) and at the
lower end of the dosage range that gives a
phytotonic effect. Another mitigating effect was
that the timing of the first of two applications 40
and 70 DE which, being late in the growth period,
would have tempered both potential effects. Each of
these factors would lead to an overestimation of
yield loss. On the other hand, none of the
insecticide treatments achieved 100% control of
insect pests in the trials offsetting the aforemen-
tioned effects.
The low yield loss of 5% on Dagge rice contrastsmarkedly with the results of the earlier studies by
Pathak and Dyck (1975) where 430% yield loss was
recorded on similar traditional varieties in the same
location. Such high losses recorded earlier were
probably due to the high rate of in-furrow carbo-
furan G (2 kg ai/ha) which would have both induced
a phytotonic response (Venugopal and Litsinger
1984) and significantly suppressed nematodes (Villa-
nueva et al. 1992), resulting in overestimates of
insect losses. Carbofuran was not used in our study
in Tanauan.
4.3. Insect pest complex
The key ecological factors of dryland sites that
affected insect species composition were the result
of: (1) an aerobic soil due to lack of soil puddling and
ponding, (2) the extensiveness of alternative plant
hosts (perennial grasslands and presence of maize or
sugarcane), and (3) nearness to wetland rice bowls.
We conclude that the most significant species
associated with loss were adapted to the non-flooded
drylands (ants, field crickets, mole crickets, white
grubs, termites) or those that survive well on grassy
weeds, or on the more dominant maize or on
sugarcane (seedling maggot, flea beetle, root aphids,
mealybugs, thrips, rice seed bugs, non-Scirpophaga
stemborers). The most important among this list were
undoubtedly ants which was the only taxon of
economic importance acting across all four sites.
Root aphids also reached economic numbers in two
sites. Seedling maggot was economically important in
all sites except for Tanauan which is devoid of
grasslands. Siniloan has extensive grassy areas
comprising the abandoned slash and burn fields
from previous seasons that only slowly return to
forest.Termites appear not to prefer living rice plants, so
are not considered economically important pests as
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dead plants were not seen. Thrips and mealybugs
were present and would have become more abundant
if prolonged drought had occurred. Rice seed bugs,
like flea beetles, reached economic importance only in
Siniloan due to their concentration in small fields.
Rothschild (1970) also attributed high numbers ofrice seed bugs in slash and burn cultivation in
Sarawak to the same factor. Both pest groups have
good local dispersive powers and can seek out small
plantings.
Puddling is a means of transforming a soil into a
muddy consistency to allow long-rooted seedlings to
be readily transplanted (DeDatta 1981). This process
of tillage and eventual ponding would kill all except
the most adapted soil-dwelling insects such as aquatic
root weevils (Lissorhoptrus and Echinocnemus) which,
only occur in flooded habitats. Our results show that
dryland soil pests are mainly those that cannot
tolerate sustained flooding. There are only limitedrecords of soil-dwelling pests such as termites, mole
crickets, and ants occurring in the wetlands. They
exist primarily when there are large bunds that
provide an aerobic environment from where they
can make temporary incursions into the field during
periods of low water saturation but cannot sustain
themselves (Way et al. 1998). Flooding is in fact a
control method for these pests (Litsinger 1994).
Polyphagy is one of the most distinguishing fea-
tures of dryland rice insects (Litsinger et al. 1987a) and
is exhibited by most of the prevalent species. The only
monophagous insect pest encountered in significantnumbers in dryland rice was the white stemborer.
Whitebacked planthopper has a wide host plant range
compared to the monophagous but more infamous
brown planthopper which it outnumbered in the
drylands. The host plant range of N. virescens is
primarily Oryza spp., whereas N. nigropictus could
persist in the drylands on perennial grasses.
The dryland site with the highest measured pest
densities was in Claveria which has large tracts of
wild perennial grasslands which grow quickly with
the first rains of the wet season enabling pest densities
to build up rapidly. In Brazil for example, the
extensive pasture lands surrounding tracts of dryland
rice are responsible for build up of a number of pests
such as spittle bugs which disperse to rice with
devastating effect (Litsinger et al. 1987a). Both Tupi
and Tanauan are highly cultivated areas where
dryland rice occupies a smaller footprint than the
surrounding maize and sugarcane; thus, immigration
can be significant by more dispersive species, i.e.
seedling maggot, flea beetles, white grubs, mole
cricket, field crickets, root aphids, planthoppers,
mealybugs, and rice seed bugs. Ho and Kibuka
(1983) found that in dryland areas of Kenya where
rice was grown in association with maize andsorghum, the principal rice stemborers were those
species that fed on all three crops.
Aestivation is a mechanism enabling survival
during a long dry season and S. innotata has the
ability to enter this diapause state for up to a year
(Litsinger et al. 2006a). No other Asian stemborer has
this adaptive trait and the ability to diapause is
probably the reason that in Sarawak, Rothschild(1971) found it to be the most abundant stemborer in
slash and burn rice. But despite this adaptation, its
numbers were lower than other stemborer species in
the Philippines as determined from tiller dissections
(Jahn et al. 2007). Yellow stemborer enters quiescence
in cool climates such as N. India and Bangladesh but
not in the Philippines. Quiescence is not a true
diapause state as the insect can resume activity
rapidly from rain or land soaking (Islam 1993).
Quiescence is different than diapause in that it occurs
in direct response to an environmental change while
S. innotata enters physiological inactivity in anticipa-
tion of the change from short day lengths and cropage (Litsinger et al. 2006a). Dry season tillage in the
two Mindanao sites acts as a control measure against
white stemborer survival. Other species with known
dormancy abilities are Leptocorisa rice seed bugs,
white grubs, and rice butterflies (Litsinger et al.
1987a).
Light trap data revealed that traditional pests
emanating from wetland culture continually rained
down on dryland rice fields in all four sites essentially
year-round (Table 2). Tupi, Tanauan, and Siniloan
were situated relatively near (1020 km) to large
wetland rice bowls, whereas Claveria is more distant.Light trap data showed that dispersal of wetland rice
insect pests, even to Siniloan in the midst of a mature
tropical rainforest, occurred when rice was not even
present. The most dispersive species are brown and
whitebacked planthoppers, Cyrtorhinus, armyworms/
cutworms, locusts, and leaffolders followed by rice
butterflies, leafhoppers, and stemborers (Litsinger
et al. 1987a).
Inorganic nitrogen usage and drought stress
accounted for the abundance of some insect pests
among sites. Tanauan with highest nitrogen usage
would have favoured planthoppers and leaffolders
along with stemborers, as noted by studies done in
wetland rice culture (Litsinger 1994). The beneficial
effects of nitrogen on planthoppers have been higher
fecundity, greater survivorship, and increased feeding
rates while those for leaffolders were egg recruitment
(ovipositing moths are attracted to the most vigorous
growing fields) and survival (Kraker et al. 2000).
Rothschild (1970) also found leaffolders on dryland
rice to be more abundant in fields of high N