Pulse Crop Insect Pests Kevin Wanner Assistant Professor of Entomology Cropland Extension Entomologist In cooperation with: Jan Knodel Assistant Professor of Entomology NDSUNDSU ExtensionExtension North Dakota State University ServiceService Integrated Pest Management – IPM Overview - Five Common Economic pests: 1.Grasshoppers Damage: 2.Cutworms . Stand thinning 3.Lygus bugs . Defoliation 4.Pea aphids . Yield and seed quality 5.Pea leaf weevil . Vector viruses 1. Grasshoppers Currently in a cycle of increasing 2007 populations: USDA-ARS Hazard Maps for Montana. 2007: 1 million acres with >15 grasshoppers per square yard. 2009 2010: 17 million acres with >15 grasshoppers per square yard. Weather can impact predictions ! 2010 Order Orthoptera. Four common species that damage crops: migratory, Melanoplus sangunipes clear-winged, Camnula pellucida two-striped, Melanoplus bivittatus red-legged, Melanoplus femurrubrum two-striped 5th instar two-striped adult migratory clear-winged red-legged Grasshoppers – General Biology Egg, nymph and adult stages (incomplete metamorphosis – gradual change). About 60-70 different species found in Montana. Smaller number of common species that move into and damage crops. Eggs are laid in pods, 8-30 eggs per pod depending on species. Eggs are deposited in the soil in grassy areas (typically not in tilled soil). Eggs are laid during the summer and are the over wintering stage. Only a few species in Montana over winter as nymphs. Nymphs develop through five instars before becoming adults. Only the adults have wings. Nymphs and adults can cause damage. Depending on species there are host preferences, but at high populations grasshoppers can eat almost any type of plant. Scouting Times July – August Observe adult migration May – June Scout early for nymphs on field edges NDSUNDSU ExtensionExtension ServiceService August – Sept Locate egg-laying sites Grasshoppers - Damage & Thresholds Damage: 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 the yield. Monitoring: Square foot method: visually count the number of grasshoppers In 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 field or > 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 electronic identification key for grasshoppers. Lucid key available online. 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 Rocky Mountains. Females lay eggs on or just below the soil. Eggs hatch (AC & DC) , larvae feed and overwinter. PWC eggs may hatch, but typically hatch in the spring (eggs overwinter). Larvae are nocturnal. AC & DC feed above ground, PWC feed below or at soil surface (cutting). AC know to migrate, damage can occur on field margins. Cutworms - Damage Monitoring & Thresholds: Pheromone traps for adults in the late summer. More than 800 army cutworm moths trapped 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. Cutworm Resources: www.cutworm.org 3. Lygus Bug adult • 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. NDSUNDSU ExtensionExtension ServiceService nymph 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. NDSUNDSU ExtensionExtension ServiceService Lygus Bug Damage on Peas/Lentils Chalk spot Pitted depression Downgraded to lower grade Deteriorate faster in storage Reduced germination Damage caused by adult and nymph life stages NDSUNDSU ExtensionExtension ServiceService Chalk Spot on Peas Undamaged Pea Damaged Pea NDSUNDSU ExtensionExtension ServiceService Chalk Spot on Lentils Damaged Lentils NDSUNDSU ExtensionExtension ServiceService 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. NDSUNDSU ExtensionExtension ServiceService Pea Aphid • Description: – Small, about ⅛ inch long. – Pale green. • Natural control: – Ladybird beetles. – Lacewings. – Syrphid flies. • Wet weather: – Diseases. – Heavy rains. NDSUNDSU ExtensionExtension ServiceService Pea Aphid Antennae reaching past the cornicles, dark bands at the segments. Ladybird Beetles - Aphid Predators larva pupa NDSUNDSU ExtensionExtension ServiceService Parasitic Wasps - Lay eggs in the aphid. “mummy” . empty shell of aphid after parasite leaves NDSUNDSU ExtensionExtension ServiceService 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. NDSUNDSU ExtensionExtension ServiceService Pea Leaf Weevil Sitona lineatus (Coleoptera: Curculionidae) Adults (3.6-5.4 mm) feed on leaves. At higher populations defoliation of small seedlings can be severe. Damage may be more pronounced during cool springs. Larvae feed on the nitrogen fixing root nodules. Primary damage. Reduced growth and yield loss. Pea Leaf Weevil - Distribution Native to Europe and North Africa; introduced to North America most 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 USA in 1984; reported in Florida in 2002. Has become a significant pest in Alberta (first detected in 1997). Ongoing surveys suggest continued range expansion northward and eastward. Reported in southern Saskatchewan for the first time In 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 Southern Alberta Northern Alberta 2006 2008 Saskatchewan 2007 2009 Pea Leaf Weevil - Biology Adults overwinter in shelterbelts or near perennial legumes. Emerge during 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 in the 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 inside the 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 leaf stage some defoliation can be tolerated. Further research is required. Difficult to correlate leaf notching with root nodule damage. Acknowledgements NDSUNDSU ExtensionExtension ServiceService Bugwood.org Jan Knodel, NDSU.