Pulse Crop Insect PestsPulse Crop Insect Pests. Kevin Wanner. Assistant Professor of Entomology. Cropland Extension Entomologist. NDSU Extension Service NDSU Extension Service. Jan

Pulse Crop Insect PestsKevin Wanner

Assistant Professor of EntomologyCropland Extension Entomologist

NDSUExtensionService


Jan KnodelAssistant Professor of EntomologyNorth Dakota State University

In cooperation with:

Integrated Pest Management – IPM

1.Grasshoppers2.Cutworms3.Lygus bugs4.Pea aphids5.Pea leaf weevil

Damage: Stand thinning Defoliation Yield and seed quality Vector viruses

Overview - Five Common Economic pests:

1. Grasshoppers

2007

2009

2010

Currently in a cycle of increasing populations: USDA-ARS Hazard Maps for Montana.

2007: 1 million acres with >15 grasshoppers per square yard.

2010: 17 million acres with >15 grasshoppers per square yard.

Weather can impact predictions !

migratory, Melanoplus sangunipesclear-winged, Camnula pellucidatwo-striped, Melanoplus bivittatus

red-legged, Melanoplus femurrubrum

Order Orthoptera. Four common species that damage crops:

two-striped 5th instar two-striped adult

clear-winged

red-legged

migratory

Grasshoppers – General Biology

Egg, nymph and adult stages (incomplete metamorphosis – gradual change).

About 60-70 different species found in Montana. Smaller number of commonspecies that move into and damage crops.

Eggs are laid in pods, 8-30 eggs per pod depending on species. Eggsare deposited in the soil in grassy areas (typically not in tilled soil).

Eggs are laid during the summer and are the over wintering stage. Onlya few species in Montana over winter as nymphs.

Nymphs develop through five instars before becoming adults. Onlythe adults have wings. Nymphs and adults can cause damage.

Depending on species there are host preferences, but at high populationsgrasshoppers can eat almost any type of plant.

July – AugustObserve adult migration

August – SeptLocate egg-laying sites

May – JuneScout early for nymphs on field

edges

Scouting Times



Grasshoppers - Damage & ThresholdsDamage: Dry peas are not preferred but seedlings can be damaged,particularly along the field margins. Lentils: grasshoppers can eat the first buds and flowers. Grasshopper heads can contaminate theyield.

Monitoring: Square foot method: visually count the number of grasshoppersIn a one square foot area. Randomly repeat 18x and divide by 2 to give # per square yard.

Treatment Thresholds: guidelines based on number of grasshoppers(nymphs and adults) per square yard.

Peas: Treatment is required if there are 8-15 per square yard within the fieldor > 20 per square yard around the field margin.

Lentils during flowering: 2 per square yard !

Grasshopper Resources:Everything (almost) that you want to know about grasshoppers:http://www.sidney.ars.usda.gov/grasshopper/

High Plains IPM Guide:http://wiki.bugwood.org/HPIPM:Main_Page

Including an electronicidentification key for grasshoppers.Lucid key available online.

http://www.sidney.ars.usda.gov/grasshopper/

http://wiki.bugwood.org/HPIPM:Main_Page

2. Cutworms Order Lepidoptera, Family Noctuidae.Three main species in Montana:

Army Cutworm, Euxoa auxiliaris

Pale Western Cutworm, Agrotis orthogonia

Dingy Cutworm, Feltia jaculifera

Cutworms - Biology

August – October, moths fly and mate.

Trivia: AC moths can migrate to high elevations in the RockyMountains.

Females lay eggs on or just below the soil. Eggs hatch(AC & DC) , larvae feed and overwinter. PWC eggs mayhatch, but typically hatch in the spring (eggs overwinter).

Larvae are nocturnal. AC & DC feed above ground, PWCfeed below or at soil surface (cutting). AC know to migrate,damage can occur on field margins.

Cutworms - Damage

Pheromone traps for adults in the late summer. More than 800 army cutworm mothstrapped in the fall may lead to damaging numbers of larvae in the spring. PWC, threshold is > 200. Need to scout larvae in the spring when crops are emerging.

Larval threshold, 2-3 per square yard.

Monitoring & Thresholds:

Cutworm Resources:www.cutworm.org

http://www.cutworm.org

adult

nymph

• Small (1/4 inch), cryptically colored insects.

• Distinctive yellow triangle or “V”.• Pale green to reddish-brown.• Immature states (Nymphs) look

like aphids.• Adult overwinter.• Feed on over 385 crops and

weeds.

3. Lygus Bug



Lygus Bug - Biology• Moves from alfalfa, CRP, roadside that are being

hayed or cut or other crops (canola, sunflower).

• Adults enter pea/lentils at bloom stage to feed and lay eggs.

• Piercing-sucking mouth parts.

• Older nymphs and adults suck out the contents of developing seeds and inject a toxic saliva into plant.

• Hot, dry weather increases populations.

• Significant quality losses in 1997 and 2002 to ND pulse crops.



Lygus Bug Damage on Peas/Lentils

Chalk spotPitted depressionDowngraded to lower gradeDeteriorate faster in storageReduced germinationDamage caused by adult and nymph life stages



Chalk Spot on PeasUndamaged Pea Damaged Pea



Chalk Spot on LentilsDamaged Lentils



Lygus Bug Monitoring& Thresholds

• When to Monitor fields:– Sweep fields during bloom-pod.– Warm, sunny 2-6 PM.– 5 locations in the field.– 25 - 180 degree sweeps with

the net in the canopy. (Not just the top of the canopy with net).

– Economic Threshold =7-10 Lygus bugs/25 sweeps.



Pea Aphid• Description:

– Small, about ⅛ inch long.– Pale green.

• Natural control:– Ladybird beetles.– Lacewings.– Syrphid flies.

• Wet weather:– Diseases.– Heavy rains.



Pea Aphid

Antennae reaching past thecornicles, dark bands at thesegments.

larva

pupa

Ladybird Beetles - Aphid Predators



Parasitic Wasps

“mummy” . . .empty shell of

aphid after parasite leaves

- Lay eggs in the aphid.



Pea Aphid –Thresholds (ND)

• Sweep net when fields are beginning to bloom through to pod set. 9-12 aphids per sweep during 50% plants with young pods.

• Lentils = 30-40 aphids per sweep.

• OR, Peas, >10 aphids on plant between 10th node and first flowering.

• If many natural enemies are present, resample 2 days later to estimate population trend.



Pea Leaf Weevil

Sitona lineatus (Coleoptera: Curculionidae)

Adults (3.6-5.4 mm) feed on leaves.At higher populations defoliation of smallseedlings can be severe. Damage may bemore pronounced during cool springs.

Larvae feed on the nitrogen fixing rootnodules. Primary damage. Reducedgrowth and yield loss.

Pea Leaf Weevil - DistributionNative to Europe and North Africa; introduced to North Americamost likely by import industries (cut flowers for example).

First reported in the Pacific Northwest during the 1930s; quickly spread to California and Idaho. First reported in northeastern USAin 1984; reported in Florida in 2002.

Has become a significant pest in Alberta (first detected in 1997). Ongoing surveys suggest continued range expansion northward andeastward. Reported in southern Saskatchewan for the first timeIn 2007.

Recent range expansion in western Canada (by flight) likely related to an increase in production area. Field pea, 198,000 ha planted in 1991 and 1.3 million ha planted in 2005.

Pea Leaf Weevil - Distribution

2007

2006 2008

2009

Southern Alberta

Saskatchewan

Northern Alberta

Pea Leaf Weevil - Biology

Adults overwinter in shelterbelts or near perennial legumes. Emergeduring during March and April and migrate to legume crops when temperatures exceed 13°C.

Field pea and broad beans are the preferred host; mating occurs inthe crops and egg laying peaks when temperatures range from 12-22 °C. Eggs are scattered over the soil surface.

Five larval instars, all feed on root nodules. First instars burrow insidethe root nodule.

Pupate in the soil. Adults emerge during the summer and feed on a variety of secondary hosts. Dispersal flight and search for overwintering sites in the fall.

Pea Leaf Weevil – Damage & Thresholds

Scalloped appearance to leaves.

Scout early.

Threshold: More than 25% of leaves are notched. After 6 leafstage some defoliation can betolerated.

Further research is required.

Difficult to correlate leaf notchingwith root nodule damage.



Acknowledgements

Bugwood.org

Jan Knodel, NDSU

Documents

Pulse Crop Insect PestsPulse Crop Insect Pests. Kevin Wanner. Assistant Professor of Entomology. Cropland Extension Entomologist. NDSU Extension Service NDSU Extension Service. Jan