Biocontrol of Seed
Predators On-Farm Using
Nematodes
Ed Lewis
Departments of Entomology and
Nematology
University of California – Davis
Seed Weevil Adults
Photo: Jim Cane
Entomopathogenic nematodes are insect
parasites
http://www.biconet.com
www.bioplanet.it/en
R. Gaugler
Commodities and Targets
• Citrus (soil application)
– Diaprepes root weevil, Diaprepes abbreviatus
• Turfgrass (soil application)
–
–
–
–
Blue green weevils, Pachnaeus spp.
Scarab larvae: e.g., Japanese beetle, Popillia japonica
Black cutworm, Agrotis ipsilon
Mole crickets, Scapteriscus spp.
• Borers (applied to plant surface)
– Iris borer, Macronoctua onusta
– Peach tree borer, Synanthedon pictipes
Commodities and Targets
• Greenhouse and Nursery production (variable)
– Black vine weevil, Otiorhynchus sulcatus
– Scarab larvae
– Fungus gnats: e.g., Sciaridae
• Mushroom Production (applied to substrate)
– Fungus gnats: e.g., Sciaridae
• Home Owners (soil application)
– Turf pests
– Fleas
Infective Stage Juvenile
Steinernema carpocapsae
Symbiotic Bacteria Released
Bacterial Chamber
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
New Infective Juveniles
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 Juveniles are what is
inside the products
Products
Sponge
2 Months (Refrigerated)
Dry Granules/Clay
2-5 Months (Room Temp.)
Vermiculite
Liquids/ gels
3-5 Months (Refrigerated)
Challenges
•
•
•
•
Short shelf life
Application methods
Tolerance to environmental conditions
Matching nematode species to target
How Long Do They Last?
Formulation Type
• Active nematodes
25º
Refrigerated
<1 week
1-6 months
1 week
2-3 weeks
– Sponge, Vermiculite
• Reduced Mobility nematodes
– Gels, Liquid Concentrates
• Anhydrobiotic nematodes
1-5 months 4-12 months
– Granules, wettable powders
• Formulated Cadavers
until nematodes begin to
emerge
Challenges
•
•
•
•
Short shelf life
Application methods
Tolerance to environmental conditions
Matching nematode species to target
Application Equipment
•
•
•
•
Self-propelled sprayer systems
Spray irrigation systems
Hand-held boom sprayer
Watering cans
• Trickle tube irrigation systems
• Injection systems
Sprayers
Keep water/nematode mix
agitated
Remove all filters from
sprayer
Keep pressure less than
2070 kPa
Maintain temperature < 30º
Do not save left-over
product
Irrigation
Monitor to be sure that IJs
reach the end of the
irrigation line
Minimize time of IJs inside
pipes, hoses, etc.
Flush lines at the end of the
application
Same limitations on filters
and pressure
Challenges
•
•
•
•
Short shelf life
Application methods
Tolerance to environmental conditions
Matching nematode species to target
Soil Type and EPNs
• Nematodes’ efficacy influenced by soil
type
• Soils in CA are extremely diverse
– Nematodes will work in some places but not
others
• Since nematodes are expensive it is
important to avoid trying to use them
where the soil will reduce their efficacy
S. riobrave – Efficacy Bioassay
1000
10 cm
800
600
Number of S. riobravae ( SE)
400
200
0
400
25 cm
300
200
100
0
400
50 cm
300
200
100
0
1
2
3
4
5
6
7
8
9
1 11 12 13 14 1 16 17 18 1 20 21 22 23 2 25 26 27 28 29 30 31 32 33
0
5
9
4
Soils
Also Must Consider
• Temperature
• Moisture of Soil (or any substrate)
• Exposure to Sun
Challenges
•
•
•
•
Short shelf life
Application methods
Tolerance to environmental conditions
Matching nematode species to target
Host Finding Important to
Understand
• Searching behavior determines host
range
• Matching searching behavior with host
behavior increases chances for
success
Where We Are
• Nematodes do infect and kill seed weevils
What We Need
• Annual timing of application
– When is a susceptible stage present?
• Choosing best nematode species
– 6-7 commercially available
• Soil testing of application sites
• Finding native nematodes