Wisconsin Vegetable Insects

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Wisconsin Vegetable Insects

• Onions

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Healthy Onions
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Onion Maggot Damage
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Onion Maggot Larvae
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Life Stages of the Onion Maggot
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Onion Maggot Pupae
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Scouting Suggestions

• Accumulate degree days beginning when the ground
  thaws in spring.
• Use a base temperature of 40 degrees
• Spring generation 680 DD40
• Summer generation 1950 DD40
• Fall generation 3230 DD40

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Degree Day Calculation

• (High temp Low temp) ? 2 Daily Average
  Temperature
• Daily Average Temperature - 40º Degree Days
• Degree days Cumulative DD total new DD total

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Cultural Control Strategies

• Crop rotation
• Eliminate crop debris at the end of the season to
  destroy overwintering pupae
• Eliminate cull and volunteer onions
• Plant onion as late in the season as possible

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Chemical Controls (Commercial)

• Apply insecticides at planting
• Foliar insecticides to control adults is not
  effective
• Limit insecticide applications to conserve
  beneficial insects
• Rotate insecticide classes to reduce the
  likelihood of resistance

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Onion Thrips Damage
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Onion Thrips
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Onion Thrips Control

• Check plants regularly, especially during hot,
  dry weather
• Remove plant debris in the fall
• Plant onions with an open type of growth and
  circular leaf structure and glossy foliage to
  reduce damage

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Onion Thrips Control - Chemical

• Foliar sprays once thresholds have been exceeded
  (7-10/plant)
• Synthetic pyrethroids are most effective
• Avoid early season pyrethroid use
• Good coverage aimed toward the base of the
  foliage will improve control

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Aster Yellows on Onions
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Aster Yellows Symptoms on Onion Flowers