Scouting and Management Challenges for Soil Insect Pests

of Peanut

Ayanava MajumdarExtension Entomologist, ACES

Gulf Coast Research and Extension Center8300 State Hwy 104, Fairhope, AL 36532

Email: azm0024@auburn.eduCell phone: 251-331-8416

Fax: 251-990-8912

What attract insects to peanut pods?Insect types:Foliar insectsSoil-air interfaceExclusively soil dwelling

CO2

HEATEXUDATES

Burrower bugs• Host range: peanut, cotton,

strawberry, spinach, wild plants• Identification: note wing structure,

scutellum, & spines on legs

• Damaging stages: adult, nymph

• Mouthparts are inserted into maturing kernel

• Cause light yellow/brown feeding spots OR “pitting”

• Loss in kernel weight and no. of sound kernel

• Increasing problem in conservation tillage systems

Hemiptera: Cydnidae

Scouting techniques (burrower bugs)• ET = 2 bugs per three feet row

• Monitoring period: July – Aug.

• Direct examination of pods (after the full seed, R6, stage)

• Underutilized techniques: spade sampling/soil corer ?, light trap ?, pitfall trap √

Pitfall trap with metal guide & cover

Spade sampling

Southern corn rootworm• Host range: 200 host plants, major pest of

corn, sweet potato, peanut

• Identification: wing pattern on adult beetles, larvae have 3 pr of legs

• Damaging stage: larvae

Stand loss (early season damage)

Larvae make a hole on one side of the pod and feed on kernel

High OM, heavy soil >> high risk

Coleoptera: Chrysomelidae

Scouting techniques (southern corn rootworm)

• ET: fresh damage evident OR larvae present in 1/3rd sites

• Electronic risk index by NCSU >> high risk (score 70+) in wet years, low risk (score <50) in well-drained soil

• Larval infestation – scout close to pegging stage

• Sweep net sampling for adults is reliable (10 sweeps/10 paces X 5 loc./A)…midmorning

• Check pods for circular holes at one side (asymmetric)

Lesser cornstalk borer• Occurrence: one of the major insect

pests of peanut, sporadic

• Host range: wide, hot-spots in peanut

• Identification: larvae are blue-green with purple bands. Moths are grayish.

• Larvae makes sand tubes on pods and stem (protection?)

• Damaging stage: larvae feed just below soil surface

• High risk to peanut in hot dry years, sandy soil

• Worst of all…Aspergillus & aflatoxins

Lepidoptera: Pyralidae

Scouting techniques (lesser cornstalk borer)

• ET – control when fresh damage is present OR when insect is recovered from 1/3rd sample sites

• Pod sampling – reliable indicator of infestation

• Scouting maps available from AWIS website – based on the estimation of borer days on a scale of 0 to 5

Wireworms• Host range: several plants (extended life

cycle allows use of resources)

• Identification: larvae with cylindrical body, wriggle furiously when touched, adults are click beetles

• Damaging stage: larvae feed at various depths, major problem following sod

• Saturated soil causes migration & spread

• Make a large entry hole on one end

Coleoptera: Elateridae

Scouting techniques (wireworms)• Study field history – crop rotation, previous infestations

• Germinating seed bait stations in soil – a reliable “relative sampling” technique

• Seed baits could be deployed before planting peanut

• Accuracy of seed baits improves with number of baits and experience of the field personnel

• ET = 1 wireworm per bait station OR 30% pod damage

Whitefringed beetles• Occurrence: native of S. Am.,

Naupactus species complex

• Host range: 350 host plants – peanut, cotton, cowpea, alfalfa, okra

• Identification: weevil w/out snout, adult has white stripes on sides, larva plump with strong mandibles

• Damaging stages: larvae/grubs

• Larvae make irregular holes in tap root, fatal to plants

• Scouting: sweep net for beetles, leaf notching (visual scouting)

• No insecticide registered

Coleoptera: Curculionidae

Cutworms• Host range: over 60 crops and turf, major

pest of peanut

• Identification: greasy plump caterpillars, larvae curl when touched

• Overwintering stage: larva• Damage:

• cut seedlings at night, may climb plants• larvae bore into the middle of peanut

pod (large hole)

Lepidoptera: Noctuidae

Black CW

Granulate CW

Other sporadic insect pestsWhite grubs(Phyllophaga spp.)

May/June Beetles1-4 year life cycleProblem after sod

Bahiagrass borer(Derobrachus brevicollis)

Large head of larvaProblem after bahiagrass

Scouting recommendations

• Draw soil samples in Winter or Spring.• Reduce tendency to overestimate – increase sampling

locations/numbers! • Use a variety of sampling methods – pheromone traps and

germinating seed bait stations are cost effective!• Economic thresholds:

Burrower bug = 2 bugs per 3 foot row

LCB, SCRW = fresh damage or insect at 30% sites

Wireworms = 1 per bait station or 30 % pod damage

Management of soil insects (peanut)

Cutworms

Indoxacarb

Cyfluthrin

Gamma-cyhalo.

Lamdba-cyhalo.

Methomyl

Zeta-cypermeth.

LCSB

Chlorpyrifos (banded over row and pegging zone)

SCRW

Chlorpyrifos (banded over row and pegging zone)

Wireworms

Chlorpyrifos (preplant broadcast spray on soil + incorporate OR banded)

Future research directions:• Extend registration of new insecticides• Focus on bio-based soil insecticides as IPM partner• Survey of all major production areas (2009)• Establish economic threshold for emerging pests

Burrower bugs

Chlorpyrifos (banded over row)

New Peanut Entomology Resources• ACES Factsheets:

– “Soil insect pests of peanut”…coming soon

– “Scouting techniques for soil insect pests of peanut”…review complete

• Timely Information sheets: (http://www.aces.edu/timelyinfo/entomology/entomology.php)

– “Germinating seed bait technique” (posted)

– “Peanut insecticide recommendations for 2009” (posted)

• New peanut entomology SharePoint: https://sites.aces.edu/group/crops/peanut/default.aspx (PowerPoint shows with narration)

• Conferences (like IPM-WC1, extension technology conf.)• YouTube Peanut Channel linked to ACES• CropsBlog: weekly updates in summer, PLEASE SUBSCRIBE!

Take home message for today…

SOIL INSECT PESTS OF PEANUT

Questions?