Unit 12: Soybean Insects

Unit 12: Soybean Insects

Carefully monitor both damaging and beneficial insects through scouting

Have knowledge of economic thresholds for insect damage and the cost of control

One insecticide application should be enough to control most infestations

Unit 12: Soybean Insects

Guidelines for insect toleration:Up to 35% defoliation during bloomingNo greater than 20% during pod filling

Leaf feeding InsectsThree pests to worry about:

Two-spotted spider mite Bean leaf beetle Soybean aphids

Unit 12: Soybean Insects

Spider Mites Feed on underside of the leaf Suck juices from the plant Symptoms

Yellow to whitish spotting on top side of leaf Webbing on underside of the leaf Severely infested leaves die

Bean Leaf Beetle Feeds on leaves causing defoliation

Unit 12: Soybean Insects

Can also feed on the pod, causing scarring and seed damage

Treat when 5-10% of pods are damaged

Larvae Can feed on roots and root nodules

Unit 12: Soybean Insects

Soybean Aphids Found for the 1st time in the U.S. in 2000 Little is known about them Eggs overwinter on buckthorn plants Can have 18 generations/yr As colonies increase, they spread Usually found on leaves and stems Feed by sucking fluid from the soybean leaves

Unit 12: Soybean Insects

Caused crinkled/cupped leaves Have reduced yields by as much as 28% in China Very difficult to treat

Weather can cause a population crash quickly Predatory control Infestation can increase 10x in a week

Insecticide may only control for small period of time May take 2 applications for control

Not treated

Insecticide applied

Unit 12: Soybean Insects

Pod & Flower Feeding InsectsCause direct yield reduction, especially if

infestation occurs late in bloomingDamaging insects

Bollworms Stink bugs Mexican bean beetle Grasshoppers

Unit 12: Soybean Insects

Green clover worm Velvet bean caterpillars

How do they cause damage?

Unit 12: Soybean Insects

Stem Feeding InsectsRarely cause economic lossesCan puncture stem to suck juicesControl measures usually not neededProblem pests

Three-cornered alfalfa hopper Weed borer

Unit 12: Soybean Insects

Seed & Seedling Feeding InsectsFeed on seed, seedling, plant roots, leavesUsually controlled with soil applied

insecticides or seed treatments

Unit 12: Soybean Insects

Damaging pests Seed corn maggot Seed corn beetle Wireworm Grape colaspis White grubs Thrips Southern corn rootworm Bean leaf beetle