West central Michigan vegetable regional report – May 11, 2016

Asparagus harvest has commenced in west Michigan, and early season vegetable pests are becoming active. Consider your transplant source to avoid problems later this season.

Frost risk

Given the forecast, there could be a risk of frost early Sunday and Monday mornings, May 15-16, if skies are clear and winds die down. Lake-effect cloud cover is expected, which should help. If clouds and wind are present, risk should be minimized.

Asparagus

Common asparagus beetle adults were detected this Monday, May 9, at the Michigan Asparagus Research Farm near Hart, Michigan. Experience suggests this pest is often first detected near wooded areas where adults overwinter. Be on the lookout for egglaying by this pest. Carbaryl and permethrin are labeled for control and have one-day pre-harvest intervals.

Cool weather and slow spear growth continue to make spears susceptible to cutworm damage in those fields where this pest is present. Oceana County growers reported finishing their first harvest early this week.

Cole crops

Degree-day models predict cabbage maggot flies have emerged from overwintered pupae in the Michigan cities of Standale, Hudsonville and Sparta. Enough degree-days could accumulate to create a predicted peak egglaying by these overwintered flies later next week.

For organic growers, row covers can prove effective and prevent cabbage maggot flies from laying eggs on plants, but are often hard to keep intact in windy Michigan. Weighting down edges can keep wind from catching edges and tearing fabric. Growers have reported they use soil, metal irrigation pipe and stones to accomplish this.

For conventional cabbage growers, consider trying VeriMark or Coragen for cabbage maggot control this year on a small portion of your acreage. Read more about these products on page 3 of Cornell University’s Veg Edge May 2015 newsletter. It is always good to get experience with new chemistries, so proven alternatives are available in an uncertain regulatory climate.

Be on the lookout for symptoms of swede midge damage in brassicas. This new pest was detected for the first time in 2015 in eastern Michigan.

Cucurbits and sweet corn

Based on degree-day models at the Hart, Hudsonville and Fremont Enviro-weather stations, seedcorn maggot adults that emerged from overwintering pupae have been flying and laying eggs since around April 20-27. Learn more about this early season pest in “Profile of a planting-time pest: Seedcorn maggot in vegetables” from Michigan State University Extension.

One non-chemical tactic to reduce risk of damage by seedcorn maggots is to delay planting of susceptible crops by 376 DD base 39 degrees Fahrenheit after peak egglaying, but before the next predicted peak. Enviro-weather can help you do this – see “New seedcorn maggot tool available on Enviro-weather” from MSU Extension.

Peppers and tomatoes

Note that vegetable transplants, for example solanaceous crops like tomatoes and peppers, will be at risk for infection with tomato spotted wilt virus and impatiens necrotic spot virus when grown in greenhouses with flowers. Infected vegetable transplants can be stunted in the field and produce distorted fruit.

Viruses can enter greenhouses on flower cuttings and plugs and then be transmitted to vegetables by thrips. Risk can be minimized when:

  • Most flowers are started from seed, since these viruses are not seedborne.
  • Flowers are grown in separate greenhouses from vegetable transplants and workers change protective coveralls between houses.
  • Growers monitor for thrips and use control measures.

Read more about thrips control in greenhouses in “Western Flower Thrips: Management on Greenhouse-Grown Crops” by Kansas State University Research and Extension. Yellow sticky cards are a cheap and easy way to monitor for this pest.

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