CHAPTER-2 REVIEW OF LITERATURE

Lot of information is available on the insect pests of forest tree species, their

status, nature of damage and period of attack, etc. Beeson (1941) and Browne (1968)

have given detail account of important forest pests. In Dehradun and Uttarakhand, Prasad

et al. (1980); Guda and Burke (1988); have listed a few insect pests in nurseries,

plantation and natural forests. Some work on pest problem in forest nurseries and their

management has been carried out by Thakur (1988). The assessment of losses due to the

insect pests and seasonal abundance of key insect pests has been studied by Guda and

Burke (1988). Champion (1934) assessed the loss to teak plantation due to teak

defoliator. Bhandari and Kumar (1993) have given an account of insect pest and their

management in agro forestry tree species.

In India, foliage destroying insects (defoliators) associated with multipurpose

trees mainly belong to four insect orders viz. (1) Lepidoptera, namely A. imparata

Walker, Ascotis acaciaria, Cusiala raptaria Walk., Hyposidra talaca Walk., Dasychira

mendosa Hubner, Lymantria mathura Moore, Lymantria semicincta Walk., Anua

triphaenoides Walk. Alleva fabriciella, Clostera cupreata, Eutectona machaeilis,

Arthoschista hilaralis, Ectropis deodarae, etc; (2) Coleopterous group, namely -

Cistelonorpha andrewesi Fairmaire, Myllocerus sabulosus Marshall, Adoretus

caliginosus Burmeister, etc. (3) Orthopterous group - represented by Acrida gigantea

Herbst and Oxya velox Fabricius and (4) Hemiptera (sap sucking insects), namely -

Drosicha stebbingii Green, Pedroniopsis beesoni Green and Laccifer lacca Kerr, etc.The

effect of insect defoliation on growth and mortality of trees has been studied by various

workers (Champion, 1934; Mathur and Singh,1954- 61; Stanley, 1965; Browne;

1968; Nicholas, 1968; Kulman, 1971; Stephens, 1971; Campbell and Valentine, 1972;

Chaudhary and Ahmad, 1972; Kegg, 1973; Campbell and Sloan, 1977; Nair et al.,

1985 and Singh and Thapa, 1988).

Defoliation has a direct effect on leaves and thus affect the growth of plant. The

leaf area is reduced depending on the number of larvae feeding. Under light to moderate

defoliation the tree survives following the production of new flush of leaves but repeated

defoliation results in serious adverse effect. The fresh leaves appear after defoliation

show reduction in size of leaf. Sometimes, repeated defoliation diminishes the whole

canopy. The defoliation has a significant effect on the terminal growth. Sometimes

defoliation can cause rapid and significant crown die back (Staley, 1965 and Nicholas,

1968).

2.1 Insect Survey and Collection:

Insect surveys are important for detecting or assessing insect population and

damage levels or document aspects of insects’ biology and behavior. Southwood (1978)

reviewed important aspects of planning and conducting insect survey and described

appropriate procedures and techniques for sampling populations. Remedial measures

prescribed to account for this disparity include using different methods of calculating

dispersion indices and selecting indices not correlated with changes in population density

(Mollet et al., 1984). An alternative method of estimating population density of an

organism is to develop a relationship between the mean density of a sampled organism

and the proportion of infested sample units, or presence-absence of sampling (Trumble et

al., 1987). This method is useful particularly for decision making, where the pest

population characteristics include high density and clumped distribution. Distribution

pattern of an insect population will be characteristically similar from year to year because

it is governed by insect’s behavior and capacity to reproduce (Royer and Edelson, 1991).

The studies of insect-plant interactions include gathering information on the

phenological, temporal and spatial relationships between insect and host plant. These

characteristics are often distinctive properties of a species (Taylor, 1984) and are

fundamentals for developing sampling protocols used in ecological and pest management

studies (Southwood, 1978), and may provide insight into other biological characteristics

of the organism (Kennedy et al., 1950; Trumble and Oatman, 1984).

2.2 Insect Plant Interaction (Host plant selection):

Insect Plant Interaction and Host plant selection by various insect pests has been

studied by several workers (Myers, 1978; Mollet et al., 1984; Trumble et al., 1987).

Outbreaks may be caused by dramatic changes in the physical environment

(Elton, 1924), genetic changes (Chitty, 1971), changes in insect-plant or

predator/parasite-pest interactions (Lotka, 1925) absence of regulating influence of their

natural enemies (Hollings, 1965; Isaev and Khlebopros, 1977).

Larvae of monophagous and oligophagous herbivore prefer the young leaf tissue

of woody perennials, while larvae of polyphagous species prefer and grow better on

mature leaves as has been observed by Cates (1980). It was observed that understory

plantation played an important role in enhancing the richness and insect diversity which

is correlated positively not only with the plant species diversity but also with architectural

plus spatial complexity (Southwood et al., 1979).

The conversion of logged over natural forests into fast growing forest plantations

can play a role in biodiversity conservation of important faunal groups, when compared

with the total clearance for agriculture or cash crop plantation (Holloway and Strok,

1991).

Natural forests are capable of regulating the fluctuating upward trend of the pest

populations while the situation under massive monocultures is invariably unstable and

pose many serious pest problems. At times, even some of the insect species, considered

to be of no economic value, assume serious pest status. There is yet another group of

insect pests which develops fancy and shift to more palatable hosts, e.g., Celosterna

scabrator in Eucalyptus, Clostera cupreata, C. fulgurita and Apriona cineneria in poplars

(Singh, 1990).

Pimental (1996) demonstrated the wisdom of Marchal’s statement by showing

experimentally that several insect species attained outbreak status in single species

planting of crucifers but did not do so in mixed species plantings, Natural forests are

capable of regulating the fluctuating upward trend of the pest populations while the

situation under massive monoclutures is invariably unstable and pose many serious pest

problems. At times, even some of the insect species, considered to be of no economic

value, assume serious pest status. There is yet another group of insect pests which

develops fancy and shift to more palatable hosts, e.g. Celosterna scabrator in Eucalyptus,

Clostera cuperata, C. fulgurita and Apriona cineria in poplars (Singh, 1990). The arctiid

Spilosoma obliqua, hitherto known only as a sporadic pest, has now assumed the status of

serious pest on different vegetable crops. 28 different cauliflower hybrids, none was

found immune or resistant. Hybrids having green plants with broad and comparatively

thicker leaves were the preferred food of S. obliqua while those having narrow, bluish

green upright leaves were relatively less damaged by the pest (Lal et al., 1994).

2.3 Biology of Insects:

The insect species belonging to family Geometridae is widely distributed

throughout the tropical and subtropical regions (Khan, 1995).

Little is known of the biology of this highly polyphagous pest, H. talaca found in

tropical low lands and highlands. The adult moth of H. talaca is brown in colour, with

pointed wings. Each female lays several hundred eggs in a single batch usually on the

underside of a leaf, but it may lay on the branches also. The loopers are black in colour

with 5-6 white dotted stripes across. In early stage, it possesses purplish-brown ground

colour with orange dots. Mature larva is brownish to pale-green in colour with a group of

three pink or orange dots on the side and fainter dorsal spots on each segment. The larva

feeds by eating steadily from the edge inwards or marking large isolated holes on the leaf.

The life cycle is completed in about 5 weeks during the monsoon season (July to

September) with a pupal period of 8-12 days. During November pupal period increases to

15 days; during winter pupae hibernate for about 8 weeks. The pupation occurs in the top

soil (Beeson, 1941; Browne, 1968).

Hampson (1895) described morphological features of moths of H. talaca.

Balwant Singh (1951&1956) studied its morphology in the immature stages of

Indian Geometridae (Lepidoptera).

Kumar (2000) stated that larvae are typical loopers, brown with dorsal transverse

row of white spots. Full grown larvae drop to the ground by silken threads and pupate

about 2-4 cm deep in soil. Eggs of H. talaca are iridescent and laid in clusters. H. talaca

develops within 2.5- 3.5 months.

Studies on biology of Spilosoma obliqua Walker on sunflower were studied by

Singh and Singh (1995). The duration of egg, larvae, pupae and adults of lymantriids,

Porthesia taiwana (Euproctis taiwana) and Orgyia postica on different food plant like

mung beans (Vigna radiata), soybeans and small red beans decreases with increase in

temperature. The food plant affected the rate of larval development and the number of

instars. Male and female larvae of P. taiwana reared on mung beans, had 6 and 7 instars

repectively, while they were having only 5 and 6 instars, respectively when reared on

soybean and small red beans. Whereas, male and female larvae of O. postica reared on

leaves of mung bean and small red bean had 5 and 6 instars respectively, while those on

soybean had 4 and 5 instars. The maximum food consumption was observed by the larvae

of E. taiwana on mung bean and by larvae of O. postica on soybean at a temperature of

25o C (Su, 1987). Developmental period of eggs, male and female larvae and male and

female pupae of Euproctis taiwana was 8.00, 18.50, 23.30, 9.90 and 10.20 days

repectively when reared on soybean leaves at 25o C while that of Orgyia postica it was

7.00, 19.43, 24.70, 8.28 and 5.63 days, respectively. The adult life span of males and

females of E. taiwana was 6.00 and 5.83 days and that of O. postica were 5.33 and 4.58

days respectively (Su, 1985).

2.4 Developmental Stages of Insects:

In some insect species, females have more moults than male larvae. Such cases

imply a discrepancy in developmental rates between the sexes and no attempt has been

made to study the regulation of developmental rates between the sexes, although sex

related differences in the secretory activity of some endocrine glands have been reported

in several species (Naisse, 1966; Wigglesworth, 1972; Feyereisen, 1985). Whisenton et

al. (1989) observed sexual dimorphism in developmental rates was also found during the

last larval instar of Rhodnius prolixus (Vafopoulou and Steel, 1989). Rate of

metamorphosis in Orgyia postica during postembryonic development appeared to be

sexually dimorphic. Females (larvae) underwent 4 moults while males (larvae) moulted

thrice only during their larval development. Consequently male larvae pupated earlier

than female larvae. But female pupal development was faster than that of males.

Therefore, in spite of different pupation time male and female pupae completed their

development in co-ordination to each other as has been observed by Gu et al. (1992).

The neonate caterpillar of Pseudoplusia includes possessed lower body weight

than their later instars. Such gain in weight during the successive instars at each moult is

to compensate the weight loss at each ecdysis and further to support and internal

preparedness for the next moulting and pupation (Kogan and Cope, 1974).

Waldbauer (1968) observed a decline in approximate digestibility in Bombyx with

age. A number of studies also suggested the same trend in different insect species (Bailey

and Singh, 1977; Yadava et al., 1979). However, Evans (1939a) did not find trend in the

larvae of Phalera bucephala. Vats et al. (1977) reported a gradual increase in tissue

growth efficiency up to early stage of fifth instar of Pieris brassicae, but decline in its

later stage. Bailey and Singh (1977) also reported the same trend in Mame configurata.

Ecological growth efficiency exhibited the same trend as was observed in tissue growth

efficiency. There was a consistent increase in ecological growth efficiency as reported by

(Vats et al., 1977), while (Waldbauer, 1968) reported a gradual decline of ecological

growth efficiency. However, (Bailey and Singh, 1977) did not observe definite pattern of

ecological growth efficiency in Mamestra configurata. Likewise, number of studies has

been made on the food utilization, assimilation and ecological efficiency of the larval

stages of other insects (Evans, 1939a and 1939b., Vats et al., 1977; Bailey and Singh,

1977; Yadava et al., 1979; Yadava et al., 1983; Kaushal et al., 1988).

2.5 Effect of Temperature and Humidity on Insect:

Weather and climate are commonly accepted by entomologist as dominant factors

influencing the behavior, abundance and distribution of insects (Messenger, 1959). Many

bio- climatic studies with insects have been undertaken largely on temperature as a

limiting factor in insect distribution and abundance. Effect of temperature on

physiological process within and insect indicate that thermal level leading to the fastest

development or the highest survival may not necessarily be the most suitable condition

for the species (Uvarov, 1931). There are several climatic factors which influence

survival and development process, mainly temperature and humidity conditions. Insects

are poikilothermic and such organisms are much more susceptible to the variations in

physical environment then homeothermic species (Sweetman, 1932). Insect tissues

contain a large percentage of water. To maintain the water balance and efficiency

carrying out the enzymatic function, optimum temperature and humidity is required.

Optimum temperature and humidity are also required for their reproductive activities,

multiplication, and survival, etc. Fluctuation in temperature and humidity influence vital

activities of insects and their life process like metabolism, behavior, reproduction,

embryonic development and mortality (Andrewartha and Birch, 1954).

Each insect species has a temperature range for its development, with a

normal/optimum ranging from 280C to 350C. If there is fluctuation from the optimum

temperature, the physiology of the insect is influenced. For example, if the temperature is

higher, then the feeding activity increases and if the temperature goes down then feeding

activity is retarded. Each insect species has a range of atmospheric relative humidity

(R.H.) within the limit of which various metabolic activities, pigmentation, development,

ovipositon, water relation, behavior etc. take place. The relative humidity also directly or

indirectly affects the life of insects, increasing or decreasing the development processes

and reproductive activities. The rate of oviposition of most insects increases at high

humidity, which influences egg development because there is a linear relationship

between development, time and saturation deficit. The increase in moisture level at high

temperature shows an adverse effect on hatching of the eggs and on the incubation

period. Besides this, variation in size and egg shape is also related to moisture content.

The food of insect and its nature is also correlated with fecundity. The changing

temperature also affects the secretion of enzymes and hormones, as a result the metabolic

rate of insects is directly affected. Insect pigmentation is also affected by temperature

change (Goodwin, 1952). The rate of movement varies greatly from one insect to another,

but it is higher at higher temperature (Hughes and Mill, 1974). Many observations have

been reported on the resistance and survival of insect species. Like temperature, each

insect species has a range of atmospheric humidity for its development within the limit of

which various metabolic activities, pigmentation, development oviposition, water

retention, behavior, etc. take place (Shelford, 1926).

Majority of the investigations carried out under controlled conditions on the

effects of temperature on the rate of development, longevity and fecundity of various pest

species has indicated that the life history was shorter at high temperature and gradually

prolonged with the fall in temperature (Butani, 1955; Pradhan and Bhatia, 1956;

Banerjee, 1957; Arora and Pajni, 1959; Tuli and Mookherjee, 1963). The effect of

humidity on the development of insects has indicated that in some cases including

Bagrada cruciferarum, Dermestes vulpinus and Chilotraea infuscatellus, relative

humidity was not found to affect the rate of development though the per cent survival

was affected considerably (Pradhan and Bhatia, 1956; Atwal, 1959 and Paul et al., 1962).

However, in case of Rhizopertha dominica, Triphleps sinui and Cadra cautella, relative

humidity had significant effect, both on the rate of development as well as per cent

survival of larvae (Kalkat and Sohi, 1960; Chatterji et al., 1961; Narayanan et al., 1962;

Tuli and Mookherjee, 1963).

A population is a group of interbreeding members of a species in time and space.

According to Mathur (1942), temperature and atmospheric conditions exert a great role

upon the appearance of the different stages of the insect. Although weather has obvious

effect on insect abundance and may influence fluctuations (Klomp, 1962), several studies

have provided evidence to show that insect shows seasonal changes in abundance (Owen,

1969; Emmel and Leck, 1970; Owen and Chanter, 1972; Wolda, 1977 and 1978). With

increasing atmospheric humidity in rainy season, population of the pest considerably

reduces quality and quantity of food which are the important factors responsible for

seasonal variation in insect population (Fenny, 1970). Rockwood (1974) has suggested

that during the season when most leaves mature, the insects may depend entirely on the

few new leaves available, especially during the off-season, which has a major effect on

the variation of insect population.

Temperature and moisture conditions also have a significant role in affecting

hatching percentage and the viability of the eggs and at higher levels it is the cause of egg

mortality. Larval development changes with change in temperature and humidity levels,

showing a decrease in development rate at low temperature and humidity with

development being rapid at optimum condition beyond which it is retarded and shows

mortality or less survival, Temperature and humidity together affect reproduction and

development differently than does either factor alone. Laboratory studies on the effect of

isolated, carefully controlled factors of climate of insects have been well studied by

Shelford (1926), Uvarov (1931), Allee et al. (1949).

The effect of climatic variability such as maximum and minimum temperature,

maximum and minimum relative humidity and rainfall on the life cycle were measured;

the basic objective was to evaluate the effect of these variables on the population

fluctuation Classic examples are processes intrinsic to the system, such as delayed

density responses, resistance of plant against insect, predator-prey interaction, etc.

(Chitty, 1971; Haukioja, 1980). The variables that determine the abundance and

distribution of a population in time and space constitute a population system (Berryman,

1981). Insect population is regulated both by biotic and abiotic factors. Among the

abiotic factors temperature, relative humidity and rainfall play the most important role.

Prasad et al. (2002) explained that relative humidity and atmospheric temperature play a

major role in population. The study on the initial biomass, consumption, egestion,

assimilation and tissue growth in the different larval instars of Antheraea proylei was

made by Yadava et al. (1983). The assimilation was estimated to be highest in the fourth

instar and lowest in the first instar. The rate of egesion for insect increased consistently

from first to fifth instar larvae and a highly significant correlation was shown to exist

between food consumption and the amount of faecal matter egested (Yadava et al., 1983).

Temperature is the dominant factor which controls insect development and

survival. Effect of temperature on the physiological process within an insect indicates

thermal levels leading to the fastest development or the highest survival may not

necessarily be the most suitable condition for the species (Uvarov, 1931).

The mortality in all the stages of the insect increases when the atmospheric

humidity rises during the rainy season (Beeson, 1941). Entomologists commonly accept

weather and climate as dominant factors influencing the behavior, abundance and

distribution of insects (Messenger, 1959).

2.6 Studies on Insect Population (Seasonal Abundance):

From the literature it was noted that a lot of work on population dynamics has

been carried out on many pests but the work on this pest has been not done. Ahmad et al.

(2003) also worked out on the infestation level and population trends of geometrids of

Paulownia fortunei.

It has been observed that as soon as plantations of any tree species is raised, one

or the other insects, which are quite innocuous otherwise in natural forests or state, builds

up to an outbreak level and cause severe damage. Gemelina arborea plantations in the

Shan States in Burma in 1930 had to be abandoned because of chrysomelid beetle,

Calopepla leayana. Toona ciliata in India could not succeed due to Meliaceae shoot

borer Hypsipyla robusta, while Bombax ceiba plantations as monoculture have failed

because of attack of Tonica niviferama (Singh, 1990).

Population level of an organism is determined within an ecosystem and held

within circumscribed limits by interactions, which involve both the population and the

physical conditions provided by the habitat (Bakker, 1964). Populations of most of the

insects fluctuate in an irregular manner between wide limits because of variability in the

supply of food and other resources. Thus, seasonal, cyclic and other variations of weather

exert a profound influence on the insect population (Clark et al., 1966).

Similar studies were conducted on an important geometrid defoliator Ectropis

deodarae, a serious pest of deodar, which appeared in outbreak in Lolab Valley, Kamraj

Forest Division (Jammu and Kashmir) in August 1982 (Singh et al., 1989). The standard

sampling techniques were used. In each compartment, 10 plots of 0.1 ha. were selected

randomly to cover different aspects and altitudes. In each plot, 25 per cent trees were

selected for monitoring the pest population. In order to study the pupal population, eight

pits of 30 cm3 were dug around the randomly selected plants. Four pits were dug out near

the base of plant in circular manner and four pits in the outer periphery of the circle. The

humus and soil dug out of pit was thoroughly examined. The result indicated that the

mean number of pupae per pit per compartment in different ranges of the division were

0.3 pupae per pit (Kupwara) and 0.7 per pit (North Lolab), while in South Lolab there

were 0.5 pupae per pit based on the field studies conducted. Begemann and Schoeman

(1998) monitored the population of Ascotis selenaria using light traps. The light trap

studies showed that high rainfall in late summer and autumn gave rise to high light trap

catches in October and November. The adult moth catches in August and September were

correlated with the October and November catches. The high moth activity was reflected

in light trap catches in the first week of October.

Insect surveys can detect or assess insect population and damage levels or

documents aspects of insect biology, and behaviour. Southwood (1978) reviewed

important aspects in planning and conducting insect survey and described appropriate

techniques for sampling population. Population level of organisms is determined within

the ecosystem and held circumscribed limits by interactions, which involve both the

population and the physical condition provided by the habitat (Bakker, 1964). Population

of most of the insects fluctuates in an irregular manner between wide limits because of

variability in the supply of food and other resources. Thus, seasonal, cyclic and other

variations of weather exert a profound influence on the insect population (Clark et. al.,

1966).

An alternative method of estimating population density of an organism is to

develop a relationship between the mean density of the sampled organisms and the

proportion of infested sample units (Trumble et al., 1987). This method is useful

particularly for decision making, where the pest population characteristics include high

density and clumped distribution. To explain this, it will be assumed that distribution

pattern of an insect population will be characteristically similar from year to year because

it is governed by insect’s behavior and capacity to reproduce (Royer and Edelson, 1991).

It was observed that understorey plantation played an important role in enhancing

the richness and insect diversity which is correlated positively not only with the plant

species diversity but also with architectural plus spatial complexity (Southwood et al.,

1979). Abiotic factors (temperature, RH, rainfall and sunshine) had a quantitative

influence of 30.76 per cent on the population dynamics of the pest (Kharuab et al., 1993).

The conversion of logged over natural forests into fast growing forest plantations can

play a role in biodiversity conservation of important faunal groups when compared with

the total clearance for agriculture or cash crop plantation (Holloway and Strok, 1991).

Natural forests are capable of regulating the fluctuation upward trend of the pest

populations, while the situation under massive monocultures is invariably unstable and

pose many serious pest problems. At time, even some of the insect species, considered to

be of no economic value, assume serious pest status. There is yet another group of insect

pests which develops fancy and shift to more palatable hosts, e.g., Celosterna scabrator

in Eucalyptus, Clostera cupreata, C. fulgurita and Apriona cineneria in Poplars (Singh,

1990).

2.7 Food Preference:

Studies on food preference of H. talaca have not been carried out till date, but has been

recorded on many host plant which are listed below:

Table 1: Host plants of H. talaca:

S.No. Botanical Name Common

Name Family Reference

1. Acacia catechu Khair Mimosaceae Beeson,1941; Mathur & Singh, 1954-1961

2. Aleurites sp Chinese Ink Euphorbiaceae Beeson,1941; Mathur & Singh, 1954-1961

3. Bombax ceiba Semal Bombaceae Beeson,1941; Mathur & Singh, 1954-1961

4. Cassia fistula Amaltash Ceasonalpinaceae Beeson,1941; Mathur & Singh, 1954-1961

5. Cupressus torulosa

Surai Cupreseceae Beeson,1941; Mathur & Singh, 1954-1961

6. Dalbergia sissoo Shisham Papilionaceae Beeson,1941; Mathur & Singh, 1954-1961

7. Ficus glomerata Gular Moraceae Beeson,1941; Mathur & Singh, 1954-1961

8. Hevea

brasiliensis Rubber plant Euphobiaceae

Beeson,1941; Mathur & Singh, 1954-1961

9. Holarrhena

antidysentirica Dudhi Apocynaceae

Beeson,1941; Mathur & Singh, 1954-1961

10. Lantana sp

Lantana Verbenaceae Beeson,1941; Mathur & Singh, 1954-1961

11. Mallotus

philippinensis Rohini Euphorbiaceae Ahmad et al., 2003

12. Morus alba Shahtut Moraceae Beeson,1941; Mathur & Singh, 1954-1961

13. Murraya koenigii

Karripatta Rutaceae Ahmad et al., 2003

14. Paulownia sp Kumar ;2000

15 Perilla

frutescens Banjeera Labiatae

Uniyal and Singh, 2010*

16. Quercus

leucotrichophora Baanj Fagaceae Singh & Singh, 2004

17. Schleichera

oleosa Kusum Sapindaceae

Beeson,1941; Mathur & Singh, 1954-1961

18. Shorea robusta Sal Dipterocarpaceae Beeson, 1941

19. Syzygium cuminii

Jamun Myrtaceae Beeson,1941; Mathur & Singh, 1954-1961

20. Tectona grandis Sagon Verbenaceae Beeson,1941; Mathur & Singh, 1954-1961

21. Terminalia tomentosa

Sain Combreataceae Beeson,1941; Mathur & Singh, 1954-1961

22. Toona ciliata Tun Meliaceae Beeson,1941; Mathur & Singh, 1954-1961

23. Xylia xylocarpa Irul Mimoceae Beeson,1941; Mathur & Singh, 1954-1961

*New host, recorded during the present study

Beside these recorded hosts, H. talaca has also been recorded on some horticultural

crops. viz, mango, cocao, chinchona, coffee, tea and other fruit plants (Pena et al., 2002).

It is now more than 30 years since “no one attractant alone performs the service of

guiding an insect to its proper host-plant, food or mate, and that the desired end is

achieved only by a complex array of stimuli, such as chemical, light, temperature and

humidity, acting in harmony.” Even so it so doubtful whether the full complexity of the

stimuli involved has yet been envisaged. Thus, just as as pheromones are sometimes

mixture of olfactory stimuli, whose relative proportions can vary in space, time, and from

population to population, the same is also true of the visual and olfactory stimuli used by

insects in host-plant finding (Finch, 1977, 1980; Miller and Strickler, 1984; Miller and

Harris, 1985).

Components of preference have been tested by a variety of techniques. Preference

for different plant species have been estimated from rates of alighting (Stanton, 1982),

fecundities in no-choice trials (Robert et al., 1982; Lofdahl, 1985). Rates of emigration

from particular hosts (Wint, 1983; Futuyma et al., 1984), and relative oviposition on

plants presented simultaneously (Tabashnik et al., 1981) or sequentially (Singer, 1971).

2.8 Nature and Extent of Damage:

Several workers have observed the maximum food consumption in the last few

instars of larvae as consumption is increased with increase in age and weight of different

larval stages of insect species (Chlodny, 1967; New, 1971; Schroeder, 1972 and 1973,

Migula, 1975; Bailey and Singh, 1977; Mackey, 1978; Vats and Kaushal, 1980).

Contrary to this, many investigators found decline in consumption index (CI) with the

increasing body weight (Axellson et al., 1975; Bailey and Singh, 1977; Vats et al., 1977;

Mackey, 1978; Vats and Kaushal, 1980; Scriber and Slansky; 1981).

The young larvae are more selective feeders and choose more digestible foliage

form the inter-vein portions of the leaf than the older larvae which feed more

indiscriminately (Bailey, 1976). The first instar larvae feed only on tender parts of the

leaves of the host plant which can be digested easily. The mature larvae start consuming

the resistant fibrous part of host plant, thereby resulting in the decline of Approximate

digestibility (AD) when compared with Prodenia eridaniee and P. sexta (Waldbauer,

1968) and P. ricini (Chockalingam, 1979), the silkworm showed an appreciably greater

AD. This high value of AD indicated its good digestibility or nutritional quality of its

food reflecting the compatibility of the insect and its host (Waldbauer, 1968; Scriber and

Slansky, 1981).

The functional roles of male and female larvae differ in the adult stage, which was

reflected in their food consumption and utilization. Female adults tend to be heavier than

males, indicating greater nutrient accumulation associated with their role as egg producer.

This generally results from increased food consumption by female larvae. Longer

duration of female larval period further enhance the food consumption (Beckwith, 1976;

Mackey, 1978).

The maximum food was ingested during the last or last two to three instars of

lepidopteran larvae. It has been reported that Bombyx mori (Hiratsuka, 1920) and

Protoparcce sexta (Wolcott, 1937) consumed about 97 per cent of their total food intake

during the last two instars and about 99 per cent during the last three instars. It may be

attributed to the fact that the last instar larvae accumulated the matter to tide over the

non-feeding pupal period. Besides, the defecation, assimilation and conversion of food to

body substance and the metabolism increased significantly during the last instar larvae.

This may be due to the increased activity of the larvae during the period (Hiratsuka,

1920; Waldbauer, 1968).

Host plant suitability of phytophagous insects mainly involves nutritional and

non-nutritional factors of host. Insects are known to alter their feeding behavior in

response to the changes in dietary requirements (Mattson, 1980; Scriber and Slansky,

1981; Murugan et al., 1992). It is widely recognized that mere establishment of insect

species on its host plant will not provide a clear picture with respect to the suitability of

the plant. However, an understanding of the efficiency of food utilization and the

reproductive success of a plant feeding insect provides a more conclusive picture in any

investigation relating to pest-plant interaction (Ananthakrishnan et al., 1985; Slansky,

1992).

Carne (1996) observed growth and relative gross efficiency of food utilization

eight times during the 18 days development of Paropsis atomaria larvae on the shoots of

Eucalyptus blakelyi. Growth and food consumption proceeded geometrically with time,

except during the earliest and last stages. Conversion efficiency declined temporarily

after each developmental stage till the final-instar larva approached maturity.

2.9 Control:

To control the defoliator, biological-cum-silvicultural methods followed by

chemical treatment are reported to be effective. Silvicultural practices like suitability of

soil, adequate irrigation facility, thinning at early stage so as to maintain the resistance in

the trees, formation of open stands from cutting instead of dense sowing was found to be

of very much importance. Deep irrigation at early stage induces early flush of leaves.

Before the time the leaf becomes mature, rough and tough when larvae are hatched in the

field, unable to cause damage due to their feeding habit as the larvae prefer to feed on

tender and soft foliage. Hence, synchronizing the time of foliage or flush of leaves with

the emergence or hatching of the larvae has been reported to create most suitable

conditions for their multiplication. Due to non availability of the preferred food,

population is affected. Besides this, the pure plantation (monoculture) has been found

very much susceptible to the insect attack as compared to the mixed crop by earlier

workers. In biological control, the introduction of the promising parasites in deficient,

areas is effective to minimize the damage, keeping the ecological balance. Among

important hymenopterous parasitoid, larvae parasitized due to Apanteles sp. Avya

choaspes Nixon, Camptohilipsis furtifica Wilkinson, Cedria paradoxa Wilkn, Meteorus

dichomeridis Wilk, Phanerotoma hendecasisella Cam. (Broconidae) are gregarious and

ectoparasites. In chalcid parasites, Brachymeria sp., and B. nephantides Gahan are pupal

parasite and they are internal (Endoparasite). The encyrtid parasites are Paralitomastix

varicornis Nees parasitise the larva and are endoparasites. Among dipterous parasites,

Cadurcia vanderwulpi Baranoff (Tachinidae) is larval cum pupal parasite and act as

endoparasite. The fly passes its early stages inside the host (defoliator larva) and reached

upto the last stage within the host pupa and forms the puparium outside. As regards the

predators, Creobator urbana Fabr and Dieiphobe infuscate Sauss. (Mantidae) belonging

to the Phasmida are effective bio-agents (Beeson and Chatterjee, 1935; Chatterjee, 1941;

Mathur and Beeson, 1941; Mathur, 1942; Chatterjee and Misra, 1974). A considerable

degree of natural control is brought about by parasites and predators. The chemical

methods reported effective against the pest is by application of carbaryl (Sevin) 50 WP or

fenitrothion 50 EC (0.1%) or dimethoate (0.03%) water emulsion spray solution as foliar

spray in nursery stage during June-August (Khan, 1995).

2.9.1 Commercial bio-pesticide:

The neem tree, Azadirachta indica A. Juss, is so far the most promising examples

of plants currently used for pest control. This holy tree in India, from where it originates,

now has a global distribution throughout the tropics. It is used for many purposes such as

shade tree, poles for construction, medicine, tooth sticks and as a source of insecticide.

Since the early seventies much research has been carried out on the pesticidal properties

of the neem tree and the results have been published in the form of proceedings of three

International neem conferences (Schmutter et al., 1981; Schmutter and Ascher 1984;

1987). Although the active ingredients in the neem such as the azadirachtin, are known, it

has been possible to synthesize these complex compounds. Over 300 species of insects

are controlled by neem all over the world of which 106 species are controlled in India.

The vapours of leaves of tulsi (Ocimum basilicum L.) neem (Azadirachta indica A. Juss)

and Eucalyptus (Eucalyptus rostrata Schlecht) have substantially inhibited egg

hatchability of Earias vittella (F) a notorious pest of cotton and okra in the tropics

(Butani & Jotwani, 1984), following exposure of adults to these volatiles (Pathak &

Krishna, 1986, 1987). Exposure of eggs of Earias vittella (F) to the vapour action of oils

of clove or Eucalyptus significantly lowered the hatchability which did not happen when

eggs were treated with vapours of cedarwood oil (Pathak and Krishna, 1993). Seed

extract of neem was found effective against teak leaf defoliator (Gupta & Joshi, 1995).

Neem leaf solution protected bamboo and Shisham leaves from their defoliators (Gutpa

and Joshi, 1995). Centuries ago farmers in India used neem leaves to protect their crops

from insect attack. Only recently, potential of behavioural and physiological aberrations

have been recognized and such effects are being considered as highly desirable and

deserved to introduced as the most prominent weapon in biologically intensive pest

management, which will be expected to reduce the risk of ecological backlash. During

the last two decades, neem has come under close scrutiny of scientists around the world

as the most promising source of natural insecticides against different agricultural, medical

and veterinary pests (Singh et al., 1996). Three international neem conferences have been

held (including two in Germany and one in Kenya) to discuss and deliberate upon various

biological properties of neem and their applicability (Schmutter, et al., 1981; Schmutter

and Ascher, 1984; 1987). Pradhan et al. (1963) reported that neem seed kernel possesses

extraordinary gustatory repellent properties, much higher than neem leaves, against desert

and migratory locust. Several biologically active compounds, which are chemically

diverse and structurally complex have been isolated from neem. Neem extracts from

neem oil, neem seed, neem seed kernel, neem leaf and many commercial neem

formulations like neem gold, Neemazal-F, Achook, Margosan-O, nimbin, etc. have been

evaluated against several insect pests in agriculture, forestry, medical etc. (Attri & Ravi

Prasad, 1980, Singh et al., 1996 and Agnihotri et al., 1996). Attri (1975) tested the neem

oil extractive and water extractive of neem seed kernel extract desert locust Schistocerca

greagaria and reported that neem oil extract was 40 times less effective than water

extract of seek kernel. Skatulla and Meisner (1975) reported 100 per cent mortality of

Lymantria dispar at 0.02, 0.02, and 0.5 per cent concentration of neem seed kernel exract.

The residual effect lasted in twelve days in the field when sprayed on oak leaves. The

potential of neem extracts in controlling the cabbage web worm, Crocidolomia binotalis

Zell (Hep: Pyralidae) was investigated in the laboratory and reported that 0.01 percent

methanolic neem extract showed toxic effect of the larvae (Fagoonee and Lauge, 1981).

Ladd et al. (1984) studies on effect of azadirachtin against the larvae Popillia japonica

indicated that the results showed the LD50 and LD90 of topically applied azadirachtin

were 0.1 and 0.4 µg per larva, respectively. Gujar & Mehrotra (1988) reported 0.5 and

2.0 per cent NSKE toxic to Aulacophora foveicollis Lucas which led to 50 per cent

mortality within 4-7 days whereas no mortality was found at 2 per cent concentration.

Neem seed kernel suspension @ 2 per cent or neem leaf extract @ 10 per cent were

effective for the control of castor semilooper, Achaea janata Linn. (Chari and

Muralidharan, 1985). Insecticidal effect of neem oil (Azadirachta indica A Juss) against

Corcyra cephalonica and Epilachna viginitioctopunctata were studied by Mathur and

Nigam (1996). The result showed that E. viginitioctopunctata was more susceptible than

Corcyra cephalonica as LC50 observed was 0.692 and 1.737 respectively. Koul (1985)

studied the effect of azadirachtin on larvae of Spodoptera litura and reported that first

larvae when fed on 0.5, 1, 2 and 4 ppm azadirachtin treated castor leaves caused 0.00,

16.00, 41.00 and 62 per cent mortality, respectively within seven days. Surviving larvae

when transferred to untreated leaf did not show much recovery. Older larvae were

comparatively less susceptible than first instar larvae. It was also reported that topical

application of azardirachtin (10 µg / larva) to the region caused higher mortality than

applied on lower abxominal region. Tanzubil (1996) studied effect of aqueous neem seed

extract and azadirachtin against Spodoptera exempta and recorded that 10 µg / larva

resulted in 100 per cent mortality within five days while lower doses inhibited and

disrupted moulting, resulting in the formation of larval pupal intermediate or abnormal

pupae. Bio efficacy of neemazal-F was studied against Helicoverpa armigera. LC50 and

LC90 values for 1st and second instar larvae were 0.0002 per cent and 0.004 per cent.

However, LC50 for first, second and third instar larvae were 0.005, 0.02, 0.03 per cent

when treated leaves fed for 48 hours only and 100 per cent mortality was observed at

0.004 per cent (Rao et al., 1990). Singh et al., (1996) studied toxicity of four neem based

commercial formulation viz. (such as Neemark 0.03 EC, Limonool 0.03 per cent EC,

Neemgold 0.03 per cent EC and Rakshak 0.05 EC) against first and second instar larvae

of tobacco caterpillar Spodoptera litura (Fab) in laboratory. When these products were

evaluated at 30 ppm azadiachtin level against 1st instar larvae, 16.7 and 37.5 per cent

mortality was recorded with the product neemark and limonool.

2.9.2 Eco-friendly control:

As we know that in the last three decades short sighted, unilateral exclusive and

extensive employment of synthesized chemicals for insect pest control has posed an

enormous and unfathomed contribution to the degradation of our environment.

Application of broad spectrum pesticides has shown many serious and self defeating

features. Therefore, health and environmental concerns have led to the withdrawal of a

number of such commercial pesticides. It is therefore necessary that in the current

millennium pest management studies should be based on bio-intensive biopesticides

being effective and cheaper, with no recurrent expense, entails no significant generic

counter attack in the pests in nature, does not add to the ever-growing problem of

environmental pollution, have low mammalian toxicity, are target specific, easily

accessible and are not attendant with the toxic hazards to the workers, consumers or to

our cherished and declining wild life.

Therefore, we have found a realistic option in our pest control programme i.e.

biopesticides. The science and theoretical basis of pest control using biopesticides has

made rapid strides in recent years. However, it could be far more successful and find far

greater use if adequate support were available and intensified effort could be made along

sound ecological lines. Various research papers have detailed out the state of the art

scenario of biopesticides through recent findings which could help in developing high

value market of biopesticides in future.

A persual of the literature reveals that the biological control has borne

successful results for various crop plants, tobacco, fruits, vegetables and weeds.

However, use of biopesticides in controlling insect pests is a new fact of research in

India and only limited work (Wada & Munakata, 1971; Yano, 1983; Saxena et al.,

1986 and Rao et al., 1990; Mishra and Singh, 1993) has so far been done.

Ahmad et al. (1991) have given an account on efficacy of some plant

extracts against ailanthus webworm. The commercially produced bacterium Bacilus

thuringiensis var. Kurstaki (BtK) has also been extensively evaluated in the

laboratory for the control of storage moths (McGaughey, 1976 and 1978). Gupta and

Joshi (1995) have evaluated the efficacy of 1per cent concentration of its toxin

against some major defoliators of forest tree species.

Recently, pest control by microbial pesticides is preferred because it is

environment friendly and rarely affects the ecological balance. According to Heimpel and

Angus (1963), most of the lepidopteran larvae suffer from gut paralysis after the

ingestion of Bacillus thuringiensis, cease feeding and die of septicemia within 2-4 days.

Plant extracts are of immense importance in insect pest control due to their

harmless and pollution free environmental implications. Earlier work (Mirnov, 1940;

Dixit and Parti, 1963; Ahmad et al., 1991) provide much needed guidelines to use and

exploit the toxicity potential of easily available plants which may to a larger extent help

to overcome various problems posed by synthetic insecticides.

The vapours of the leaves of tulsi (Ocimum basilicum L.), neem (Azadirachta

indica A. Juss) and eucalyptus (Eucalyptus rostrata) have substantially inhibited egg

hatchability of Earias vittella (F), a notorious pest of cotton and okra in the tropics

(Butani and Jotwani, 1984), following exposure of adults to these volatiles (Pathak and

Krishna, 1986 and 1987).

2.9.2.1 Neem:

There is lot of publications listing plants with insecticidal properties. For

example. Heal et al. (1950) reported approximately 2,500 plants in 247 families with

some sort of toxic property against insects. But to use them it is not enough that the plant

be considered as promising or even with proven insecticidal properties.

Neem extracts or derivatives used for insect control include dried leaves, seeds,

seed kernels, oil cake in aqueous or organic solvent, standardized neem rich extracts,

partially purified fractions and azadirachtin formulation, etc. McMillan et al. (1969) were

the first to report the growth disrupting effect of chloroform extract of Bakain leaves

(Melia azadirach) against Spodoptera frugiperda and Heliothis zea.

Attri (1975) tested the neem oil extractive and water extractive of neem seed

kernel extract on desert locust Schistocerea greagaria and reported that neem oil

extractive was 40 times less effective than water extract of seed kernel. Skatulla and

Meisner (1975) reported 100 per cent mortality of Lymantria dispar at 0.02 and 0.5 per

cent concentration of neem seed kernel extract. The residual effect lasted for 12 days in

the field when sprayed on oak leaves.

Neem extract viz. neem oil, neem seed kernel extract, neem leaf extract and many

commercial neem formulations like neem gold, Neemazal – F, Achook, Margosan – O,

Nimbin, etc., have been evaluated against several insect pests in the field of agriculture,

forestry etc. (Attri and Ravi Prasad, 1980, Singh et al., 1996; Agnihotri et al., 1996). The

neem seed kernel extract when applied at juvenile stages on insect, arrest their growth.

Depending on dose, the insects are either killed before reaching adult stages or produced

malformed or miniature adults.

Gujar and Mehrotra (1983) reported that the last instar larvae of Spodoptera

litura fed on castor leaf disc treated with 1 µg to 50 µg caused 12.5 – 55.5 per cent

abnormal pupae. Further they reported that 100 µg neem oil applied against pupa of

tobacco caterpillar Spodoptera litura produced abnormal adult. But neem oil at 200 µg

/pupa caused 100 per cent mortality. Neem seed kernel extracts at 10 µg /pupa caused

100 per cent mortality, while azadirachtin at 10 µg /pupa killed 33.33 per cent pupae and

produced 41.67 per cent malformed adults and 50 per cent normal adults. Sharma et al.,

(1983) studied the solvent extracts from different parts of neem tree and their effect on

larvae of Mythmna separata.

Ladd et al. (1984) studied the effect of azadirachtin against the larvae Popilia

japonica and the results showed that LD50 and LD90 of topically applied azadirachtin

were 0.1 and 0.4 µg per larvae, respectively. Neem seed kernel suspensions @ 2 per cent

or neem leaf extract @ 10 per cent were effective for the control of Castor semilooper,

Achaea janata Linn (Chari and Muralidharan, 1985). Koul (1985) studied the effect of

azadirachtin on the larvae of Spodoptera litura. It was reported that first instar larvae

when fed on 0.5, 1, 2, and 4 ppm azadirachtin treated castor leaves, caused 16.00, 41.00

and 62.00 per cent mortality, respectively within seven days. Surviving larvae when

transferred to untreated leaf did not show recovery. Older larvae were found

comparatively less susceptible than first instar larvae.

Gujar and Mehrotra (1988) reported 0.5 and 2.0 per cent NSKE toxic to

Aulacophora foveicollis Lucas leading to 50 per cent mortality within 4-7 days, whereas

no mortality was found at 2 per cent concentration of neem oil. Neem oil as a residual

film had an LC50 of 0.7 per cent concentration.

Within the last two decades, neem has come under close scrutiny of scientist

around the world as the most promising source of natural insecticides against different

agricultural, medical and veterinary pests (Saxena et al., 1986; Singh et al., 1996).

Several biologically active compounds, which are chemically diverse and structurally

complex compounds, have been isolated from neem.

Tanzubil (1996) studied effect of aqueous neem seed extract and azadirachtin

against Spodoptera exempta. It was reported that at 10 µg / larva resulted in 100 per cent

mortality within five days while lower doses inhibited and disrupted moulting, resulting

in the formation of abnormal pupae.

Methanolic extracts of dried and crushed neem and bakain seeds were evaluated

and compared with Nimbicidine. It was found that neem and bakain ( at > 2% conc.) and

Nimbicidine (0.5%) proved better than the latter and their effect was more pronounced at

higher concentrations particularly against the first instar larvae of Earias vittella (Gajmer

et al., 2002).

Munakata (1977) described the repellent action of seed or leaf extracts of neem

against the migratory locust, Locusta migratoria and the desert locust, Schistocerca

gregaria. The worker reported that meliantroil (C30 H50 O5) and azadirachtin (C35 H44

O16) inhibit the feeding of locusts. It has been to the greater extent established that with

sufficiently high doses (100 to 1000 ppm) primary antifeedant effects are significant.

The usefulness of neem and other plant products for the management of crop

disease of food and commercial crops have been demonstrated by many scientists

all over the country. Approximately 1600 plant species are recorded to possess

pest control properties (Grainge et al., 1985). Gerrits and Van latum (1988) listed

10 plant species considered most promising. Seed extract of Pongamia pimiaia was

found effective against the larvae of Ailanthus defoliators (Gupta & Joshi, 1995).

2.9.2.2 Bacillus thuringiensis:

Basillus thuringeinesis Kurstaki is a subspecies of naturally occuring bacterium,

Bacillus thuringiensis, commonly found in soil as it is used as a biological insecticide to

control crop damaging moths. It affects only leaf eating caterpillars of moths and

butterflies. This effect is specific to the caterpillars. It cannot be used to kill eggs, pupae,

or adults. B. thuringiensis Kurstaki does not kill the insect on contact, so must be ingested

to be effective. It works as an insecticide in the gut of caterpillars. The digestive systems

of humans and other mammals differ form caterpillars, and as a result, they are not

harmed by the proteins. Once inside the caterpillar’s stomach, where a basic (alkaline)

pH is present, the bacterium multiplies and releases toxic substances. Specific enzymes in

caterpillar’s stomachs are also required to activate the product. When the bacterium is

activated, the gut is paralyzed and the caterpillar stops feeding and dies within one to five

days. Larvae are most susceptible to it when they are in the early development stages.

The crystal inclusions derived from B. thuringiensis Kurstaki are generally specific

lepidopteran. Because they have to be ingested and then processed within the insect’s gut,

they are often slow acting (two to forty-eight hours in comparision to conventional

chemicals). The toxin results in starvation leading to death; insects not killed by direct

action of the toxin may die from bacterial infection over a longer period. Different toxins

have different spectra of activity. Different bacterial isolates, even in the same subspecies

may differ in their pathogenicity to a specific insect, primarily because of differences in

toxins produced by the strains (Dulmage, 1970; Dulmage et al., 1990).

Bacillus thuringiensis has been extensively used against agricultural pests

(Kurstak, 1982). Among the microbial pathogens, Bacillus thuringiensis has received

much attention due to its promising effect and wide host range (Beagle and Yamamoto,

1992). It was observed that feeding on sprayed leaves was superior than spraying the

larvae which could be accounted for higher level of ingestion of the bacteria by the insect

(Roychoudhary et al., 1994). Spraying of 2.0 per cent of B.t. var. Kurstaki (LDC) against

Pyrausta bambucivora also proved to be effective causing 100 per cent mortality after 72

hours in fifth Instar larvae (Gupta and Joshi, 1995). Two products of Bacillus

thuringiensis Berliner. var. Kurstaki endotoxin and var. dendrolimus endotoxin were

tested against Hyblaea puera a defoliator of Tectona grandis and 1.5 per cent

concentration was found most effective in controlling the pest (Kalia and Joshi, 1996b).

Laboratory bioassays were evaluated by Brousseau et al. (1998) in order to assess

the efficacy of a commercial formulation of B. thuringiensis var. Kurstaki (thuricide)

with destruxins (Metarhizium anisopliae mycotoxins) on the fifth instar of Choristoneura

fumiferana Clements. Mechanism of resistance to B. thuringiensis insecticidal crystal

protein Cry IC in the diamond back moth. Plutella xylostella L. (Lepidoptera: Plutellidae)

was studied by Liu et al.,2000. Bti was found to be relatively specific to Diptera and was

quickly shown to be toxic to a range of mosquito control agent and rising incidence of

resistance to chemical pesticides provided a platform for rapid Bti development in the

early 1980s. Products based on Bti have now been used in many countries, with extensive

mosquito and blackfly control programmes based on Bti occurring in West Africa, USA

and Europe. In particular, Bti has been used in area considered environmentally sensitive

(Federici 1995). Cry4 protein toxin genes are Dipteran – specific, as the Cyt genes. The

crystal is formed at the end of sporulation. All proteins are toxic to mosquitoes, however

there appears to be a synergistic interaction between the Cyt 1 Aa protein and the Cry4

and Cry11 proteins, resulting in high toxicity to mosquito larvae (Tanada and Kaya,

1993). Bti treated mosquito larvae generally cease feeding within 1 hours, show reduced

activity by two hours, extreme sluggishness by four hours and general paralysis by six

hours after ingestion (Chilcott et al., 1990). An understanding of the ecology of Bti in the

environment is essential in assessment of its environmental risk. Bti has been extensively

studied for effects on non-target organisms and environmental consequences of use with

no reported adverse effects (Burges et al., 1981). Field applications have often been

monitored for effects on non-target organisms but no significant non-target effects have

been reported (Colbo and Undeen 1980; Miura et al., 1980; Jackson et al. 1994;

McCracken and Matthews 1997). Merrit et al. (1989) found no detectable non-target

effects of Bti application against blackflies in Michigan. Bti is non toxic to bees (Krieg et

al., 1980) The W. H. O. (1992) reviewed a number of laboratory and filed studies that

examined the impact of Bt on frogs, news, salamanders and toads in which no adverse

effects were recorded problem. Bti failed to mutiply in mammals and ingested cell were

eliminated rapidly (Siegel and Shadduck, 1990). Extensive studies on birds and mammals

with high doses of unsolubilized Bti spores and crystals have shown no effect (Meadows,

1993).

Effectiveness of three toxins of Bacillus thuringiensis against fifth instar larvae of

shisham defoliator was tested and 100 per cent mortality was observed at 2.0 per cent

concentration after 72 hours (Kalia and Joshi, 1997). Efficacy of BIOASP and BIOLEP,

microbial insecticide was tested against teak skeletonizer, Eutectona machaeralis Walk, 2

per cent Bioasp proved to be highly effective in causing larval mortality (an average of

85.93%) followed by 2 per cent biolep which produced an average mortality of 77.54 per

cent (Kalia and Meshram, 1997).

2.10 Relative toxicity and Efficacy of Pesticides:

Relative toxicity of twenty two conventional insecticides was tested by Gupta et.

al., 1989 as direct spray against adult beetles of Calopepla leayana, a serious pest of

Gmelina arborea plantations and occurs all along the tract of its host plants.

Bioefficacy of neemazal – F was studied by Rao et al. (1996) against Helicoverpa

armigera which shows LC50 and LC90 values for first and second instar larvae were

0.0002 per cent and 0.004 per cent. However, LC50 for first, second and third instar larvae

were 0.005, 0.02 and 0.03 per cent. Growth regulatory effect is the most important

physiological effect of neem products on insect. The antifeedant and growth inhibition

effect. Food consumption and relative growth rate were decreased signigicantly with

increasing concentrations (Joseph, 2000).

Toxicity of emamectin benzoate, an avermectin semi-synthetic insecticide, was

evaluated by Birah et al., 2008 in the laboratory to determine its performance on three

different larval stages (5, 7 and 9 day old) of tobacco caterpillar, Spodoptera litura during

2007-08. Three type of assay techniques viz. leaf-dip, potter’s tower and thin-film were

used, taking three different formulations of emamectin benzoate and were compared with

conventional one i.e. cypermethrin, against the test-insect.

Souza Jr. et al. (2009) evaluated the toxicity of thirty Bt. strains which were

isolated from soil samples. Among which, strain I4A7 was most efficient against the fall

armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae).

Gupta & Joshi (1995) have evaluated the efficacy of Bacillus thuringiensis

Kurstaki (Btk), 1 per cent concentration of its toxin against some major leaf defoliators.

In laboratory, a 2 per cent suspension of BTB – 202 gave 94 per cent mortality of Tortrix

viridana, as against 89.9 per cent with a 1 per cent suspension of BTB – 202 gave 90.7

per cent mortality of L. dispar in 14 days (Okhotnikov, 1978). The lepidopteran-active

Bacillus thuringiensis Kurstaki (Btk) has been investigated for control of kiwifruit pests,

especially leafrollers (Wigley and Chilcott 1994). Bioassay to determine LC50 values of

spores and crystals of four varieties of B. thuringiensis (B. thuringiensis var. galleriae,

var. kurstaki and var. rolwathi) grown on nutrient agar plates were carried out against

neonate and 6 days old European corn borer. Ostinia nubilalis larvae (Mohd – Salleh and

Lewis, 1981). Efficacy of B. thuringiensis subsp Kurstaki (Thuricide HP), B.

thuringiensis subsp. Galleriae (Entobakterin), B. thuringiensis subsp. Dendrolimus

(dendrobacilln) was evaluated in an experiment carried out to control Stilpnotia salicis, a

serious pest of poplar stands in North West Hungary (Szalay-Marzso et al., 1981).

Lepidocide B. thuringiensis var. kurstaki was highly effective in causing mortality of

98.28 per cent against Tortrix viridana, 96.5 per cent against Euproctis chylysorrhoea, 90

per cent against Operophtera brumata and 81 per cent against Dendrolimus pini (Kuteev

et al., 1983). Misra and Singh (1993) studied efficacy of Thuricide in laboratory against

twelve important forest Lepidoptera. Studies on relative toxicity of B. thuringiensis

subsp. Kurstaki to gypsy moth, Lymantria dispar, fed with alder, Ainus rhomnifolia and

Douglas-fir, Pseudotsugata menziesti indicates that host plant may influence toxicity of

B. thuringiensis to gypsy moth (Moldenke et al., 1994). Three microbial pesticide

products based on B. thuringiensis (BTB, LDC and Dipel) were assayed against early

instar larve of poplar defoliators Clostera cupreata, Phalanatha phalantha and Botyoides

asialis (Kalia and Joshi, 1996b). The toxicity of B. thuringiensis subsp. Kurstaki (Dipel)

to different larval instars of mulberry sillworm. Bombyx mori L. was evaluated under

laboratory conditions (Kamala Jayanthi and Padmavathamma, 1997). Efficacy of three

varietal strains of B. thuringiensis Berliner against the Moringa defoliator Noorda

blitealis Tanss. (Lepidoptera: Pyralide) was evaluated by foliar spraying (Kalia and Joshi,

1997).