How to Control Soil Insects with Beneficial Nematodes
Transcript of How to Control Soil Insects with Beneficial Nematodes
How to Control Soil Insects with Beneficial Nematodes
Ed Lewis Department of Entomology and
Nematology University of California, Davis
Using Microbials in IPM • Do not have to change everything
about crop management
• Many microbial insecticides fit into current production plans with minimal effort and change
• They require specialized information about their use
Insect pathogens can be effective
• Naturally occur – Even in intensively managed
systems • Have an impact on insect
populations at natural levels
Necessary information: Products
• Shelf life • Storage conditions • Resting stage? • Viability in field • Host range • Time to kill • What does an infected insect look like?
Recognized Species of Entomopathogenic Nematodes H. bacteriophora H. brevicaudis H. hawaiiensis H. indica S. kraussei S. arenarium S. bicornutum S. carpocapsae S. caudatum S. ceratophorum S. cubanum S. feltiae S. glaseri S. intermedium S. affine
H. marelatus H. megidis H. zealandica H. argentinensis S. karii S. kushidai S. longicaudum S. monticolum S. neocurtillae S. oregonense S. puertoricense S. rarum S. riobrave S. ritteri S. scapterisci
Infective Juveniles
• Resistant to Environmental Extremes • Only Function is to Find A New Host • No Feeding • No Development • No Reproduction • Only Life Stage Outside the Host
Infective Stage Juvenile Steinernema carpocapsae
Bacterial Chamber
Symbiotic Bacteria Released
Mating for Steinernema spp.
Two to three generations occur in a single host. About 6 days after the original infection, this is the appearance
New Infective Juveniles in 10 Days
Entomopathogenic Nematodes Can Control:
• Weevils: Diaprepes root weevil, Diaprepes abbreviatus Blue green weevils, Pachnaeus spp. Otiorhynchus spp. Bill bugs
• Fungus gnats: e.g., Sciaridae
Entomopathogenic Nematodes Can Control:
• Scarab larvae: e.g., Japanese beetle, Popillia japonica, Chafers, etc.
• Lepidoptera: Black cutworm, Agrotis ipsilon Codling moth, Cydia pomonella Leafminers, Liromyza spp. Banana moth, Opogona sacchari Navel Orangeworm, Amyelois transitella
• Other: fleas, mole crickets
Some Things to Remember About Entomopathogenic
Nematode Products
Products Can Be Deceiving
• Infective Stage is NOT a Resting Stage
Live Infective Stage Nematodes
Infective Stage Survival
H. bacteriophora
S. carpocapsae
S. glaseri
Formulation Shelf-life (storage method)
Sponge 2 Months (Refrigerated)
Vermiculite 3-5 Months (Refrigerated)
Dispersable Granule 2-5 Months (Room Temperature)
How Long Do They Last?
How Do We Figure Out Where and When to Use them?
• Climate • Soil Types
Special considerations for applying microbials
• Not chemical pesticides – Storage – Application
• Special habitat requirements • Realistic expectations
– Kill slower than chemicals – Will not (usually) completely eliminate
pests
Case Study • Entomopathogenic
nematodes to manage Diaprepes abbreviatus (citrus root weevil) in Florida and California
Citrus Root Weevil Adult
Diaprepes Damage
Southport Grove, Osceola County, FL
What makes Diaprepes difficult to control?
• 270 known host plant species • asynchronous, complex, variable life
history • high fecundity, protected egg masses • many pesticides are ineffective against
soil-dwelling larvae • many natural enemies have limited,
patchy distributions
Diaprepes abbreviatus Life Cycle
Adults
Eggs
Neonates
Larvae Pupae
Perc
ent m
orta
lity
Sand Sandy Clay Loam 0
20
40
60
80
100 + S. riobrave
Untreated Field Experiment
Nematodes Most Effective in Coarse Sandy Soils
(Duncan et al., unpublished)
What to do in California?
• Soil type has major impact on efficacy • Soils in California much more diverse than
in Florida
Objective
• Develop methods to determine whether or not entomopathogenic nematodes will be effective biological control agents of citrus root weevils in CA citrus
Column Assay Units
Num
ber o
f S. r
iobr
avae
(±S
E)
Soils
0
200
400
600
800
1000 10 cm
0
100
200
300
400 25 cm
0
100
200
300
400 50 cm
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15
16 17 18 19
20 21 22 23 24
25 26 27 28 29 30 31 32 33
S. riobrave – Efficacy Bioassay
8
9
11 10 12 13
7
4 24
25
26
6 5 3
1 2
23
22
21 14
15 16
17 18
19 20
28
27
31 30
32
34
35
33
36
29
S1
S2
S3
S4
S5
Silt
C
lay
pH
EC
MR
A
B
C
D O
M
Cluster analysis: grouped similar soils based on physical and chemical characteristics
Med
ian
Num
ber o
f Nem
atod
es (±
25t
h per
cent
ile )
Efficacy of EPNs in different clusters
600
0
100
200
300
400
500 (a)
0
20
40
60
80
100
120 25cm
0
10
20
30
40
50
60
A B C D
Cluster
(b)
(c)
10cm
50cm
a a
b c
a b
c
d
a
b b
c
Using This Information
Can soilless media be constructed to enhance persistence and efficacy of microbial insecticides?
Foraging of S. riobrave in Soilless Media Components
0
2
4
6
8
10
Sand Peat Moss Cedar/PineBark
RecycledPlant
Material
Redw oodSaw dust
(w /o bark)
Redw oodSaw dust(w /bark)
Perlite Vermiculite
Dis
tanc
e tr
avel
led
(cm
)
02550
a
ab
abcabc
abcabc
bcde
deff
bcdeabcd
abc
ab
eff
bcde
ff
defcdef
ff
Foraging of S. riobrave in Soilless Media Components
0
2
4
6
8
10
Sand Peat Moss Cedar/PineBark
RecycledPlant
Material
Redw oodSaw dust
(w /o bark)
Redw oodSaw dust(w /bark)
Perlite Vermiculite
Dis
tanc
e tr
avel
led
(cm
)
02550
a
ab
abcabc
abcabc
bcde
deff
bcdeabcd
abc
ab
eff
bcde
ff
defcdef
ff
How to Make EPNs Work?
• Product quality • Product suitability
• Application rates • Application timing
• Environmental conditions • Substrate conditions