Unit 12: Soybean Insects

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Unit 12 Soybean Insects
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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

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Unit 12 Soybean Insects

• Guidelines for insect toleration
• Up to 35 defoliation during blooming
• No greater than 20 during pod filling
• Leaf feeding Insects
• Three pests to worry about
• Two-spotted spider mite
• Bean leaf beetle
• Soybean aphids

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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

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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

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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

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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

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Insecticide applied
Not treated
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Unit 12 Soybean Insects

• Pod Flower Feeding Insects
• Cause direct yield reduction, especially if
  infestation occurs late in blooming
• Damaging insects
• Bollworms
• Stink bugs
• Mexican bean beetle
• Grasshoppers

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Unit 12 Soybean Insects

• Green clover worm
• Velvet bean caterpillars
• How do they cause damage?

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Bollworm
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Mexican Bean Beetle
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Green Cloverworm
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Unit 12 Soybean Insects

• Stem Feeding Insects
• Rarely cause economic losses
• Can puncture stem to suck juices
• Control measures usually not needed
• Problem pests
• Three-cornered alfalfa hopper
• Weed borer

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Unit 12 Soybean Insects

• Seed Seedling Feeding Insects
• Feed on seed, seedling, plant roots, leaves
• Usually controlled with soil applied insecticides
  or seed treatments

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Unit 12 Soybean Insects

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

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Wireworm
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Grape Colaspis
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Seed Corn Beetle
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Seed Corn Maggot
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Thrips