How to Control Soil 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 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. marelatus H. brevicaudis H. megidis H. hawaiiensis H. zealandica H. indica H. argentinensis S. kraussei S. karii S. arenarium S. kushidai S. bicornutum S. longicaudum S. carpocapsae S. monticolum S. caudatum S. neocurtillae S. ceratophorum S. oregonense S. cubanum S. puertoricense S. feltiae S. rarum S. glaseri S. riobrave S. intermedium S. ritteri S. affine 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 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 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. • : Black cutworm, Agrotis ipsilon Codling , Cydia pomonella Leafminers, Liromyza spp. Banana moth, 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 How Long Do They Last?

Formulation Shelf-life (storage method) Sponge 2 Months (Refrigerated)

Vermiculite 3-5 Months (Refrigerated)

Dispersable Granule 2-5 Months (Room Temperature)

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

Eggs

Adults

Neonates

Pupae Larvae Percent mortality 100 20 40 60 80 0

Nematodes MostEffective in CoarseSandySoils Sand

Field Experiment Sandy Clay Loam + Untreated S. riobrave

(Duncan etal., 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 Number of S. riobravae (±SE) 1000 100 200 300 400 100 200 300 400 200 400 600 800 0 0 0 1 10 cm 50 cm 25 cm 2 3 4 5 6 7 8 9 S. riobrave–Efficacy Bioassay 0 1 11 11 12 13 14 5 1 Soils 16 17 18 9 1 20 21 22 23 4 2 25 26 27 28 29 30 31 32 33 8 7 28 30 31 Cluster 36 A 32 analysis: 24 26 4 grouped 15 16 similar soils 6 5 35 B based on 3 17 18 physical and 2 25 chemical 1 23 21 characteristics 34 C 14 27 29 33 9 19 20 22 D 11 10 12 13 S1 S2 S3 S4 S5 MR pH EC Silt OM Clay Efficacy of EPNs in different clusters

Median Number of Nematodes (± 25th percentile ) 100 120 100 200 300 400 500 600 10 20 30 40 50 60 20 40 60 80 0 0 0 (a) (b) (c) b A c b b b a B Cluster a a a C d c c D 50cm 25cm 10cm Using This Information

Can soilless media be constructed to enhance persistence and efficacy of microbial insecticides? 10 Foraging of S. riobrave in Soilless Media Components 0 8 a 25 ab 50 ab abc 6 abc abc abc abc abcd bcde bcde bcde 4 cdef def def f Distance travelled (cm) travelled Distance f f ef 2 f f f

0 Sand Peat Mos s Cedar/Pine Rec y c led Redw ood Redw ood Per lite Vermiculite Bark Plant Saw dust Saw dust Mater ial (w /o bark) (w /bark) How to Make EPNs Work?

• Product quality • Product suitability

• Application rates • Application timing

• Environmental conditions • Substrate conditions