West central Michigan vegetable update – May 16, 2018

Asparagus harvest is here in west central Michigan.

Asparagus harvest had started in earnest in west central Michigan this Tuesday, May 15. Common asparagus beetles have already been sighted over the weekend in commercial fields. Products with one-day pre-harvest intervals for beetle control include:

[Example product (active ingredient, chemical class)]

  • Assail 30G (acetamiprid, neonicotinoid class)
  • Lannate LV (methomyl, carbamate class)
  • Lorsban 4E (chlorpyrifos, organophosphate class)
  • Perm-Up (permethrin, pyrethroid class)
  • Sevin 4F (carbaryl, carbamate class)

In the past, carbaryl has been an effective choice for controlling adult beetles during harvest. Experience suggests there is little advantage to using XLR formulations of Sevin during harvest as spears with residue are being rapidly removed, so longer residual activity may not be a big benefit prior to the fern season. Assail (two applications allowed per year) has also proven effective in trials in the southeast for killing adults and preventing egglaying on spears and is a different mode of action compared to other available products.

Cutworms can also be active this time of year. White cutworm can be more active early in the season. It overwinters as a caterpillar and climbs spears to damage tips. Nicks from the mower or harvest carts can look like this damage; if damage is on spears that are all the same height, these could be the culprit. To confirm damage is from cutworm, dig around the base of damaged spears and look for caterpillars. They hide out during the day in the soil. Treatment with permethrin (one-day pre-harvest interval) can provide control.

For cole crops, cabbage white butterflies were spotted laying eggs in southeast Michigan cabbage, and I have seen butterflies flying since last week. Cabbage maggot damage from the spring generation should become apparent over the next three weeks as maggots develop from eggs laid by flies.

For cucurbits, if you have young plants in areas that have received heavy rains, be on the lookout for early plant death in fields with known Phytophthora capsici issues. As plants grow, if you see symptoms that suggest problems are developing, consider disking under hotspots plus a firewall of healthy looking plants to slow spread later in the season. Two cucurbit downy mildew spore traps are now out and spore counts should be available in one to 1.5 weeks via MSU Downy Mildew News.

For herbs, there have been reports across the country of downy mildew on basil in the greenhouse. Fungicides are available for the greenhouse, such as Subdue (greenhouse version of Ridomil), Micora and Ranman. Look for symptoms in your basil; turn the leaf over looking for dark, fuzzy sporulation. At times, the upper surface of the leaf will turn yellow with corresponding sporulation underneath, but this does not always occur.

Hops suffer from downy and powdery mildew. This year, some growers have taken a cue from western growers and cut back the initial flush of growth. Both diseases are systemic and sporulate on new shoots in the spring to start infection cycles. The hope is that cutting back the initial flush could slow disease development.

MSU Diagnostic Services has been receiving samples of pepper and tomato transplants with bacterial disease. Read more about managing these diseases in the greenhouse in “Protect greenhouse tomato transplants from bacterial spot” by MSU Extension

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