West central Michigan vegetable update – April 26, 2017

Asparagus has emerged on row ends and planting activity is ongoing in west central Michigan.

Asparagus spears emerging on row ends in a rye cover. Rye cover crops are herbicide-killed and mowed. Roots hold soil and reduce damage from windblown sand. All images courtesy of Ben Werling, MSU Extension.

Asparagus spears emerging on row ends in a rye cover. Rye cover crops are herbicide-killed and mowed. Roots hold soil and reduce damage from windblown sand. All images courtesy of Ben Werling, MSU Extension.

Asparagus first emergence of spears was reported April 16 in Oceana County. Spears were up on row ends last week (see photo). Growers have been focusing on finishing spreading pre-harvest fertilizer, finishing glyphosate application to rye and making pre-harvest herbicide applications.

Once harvest starts, be on the lookout for white cutworm damage. This cutworm climbs emerging spears and feeds on tips. Most growers apply chlorpyrifos pre-harvest to control this pest and dark-sided cutworm, which becomes damaging later. Experience suggests damage is very spotty. Applying permethrin is also effective and could be made based on scouting. Note that harvest carts can nick spear tips, so be sure to dig around the bases of plants to look for caterpillars before making additional insecticide applications this season.

Carrot planting of processing carrots started in Oceana County over the past week.

Celery planting has been ongoing under frost cover.

For cole crops, cabbage and turnip planting was ongoing at some Ottawa County locations. Degree-day models on Michigan State University’s Enviroweather are predicting cabbage maggot flies will emerge from overwintering pupae in the next week based on weather at the Hudsonville, Sparta and Standale stations.

Are you growing organic leafy brassicas this year? Key pests growers face year after year include flea beetles as well as three caterpillar species, diamondback moth, imported cabbage worm and cabbage looper. Cornell University’s organic cole crop production guide suggests using organic insecticides that target caterpillars such as Bacillus thuringiensis subsp. kurstaki (e.g., Dipel, Deliver) and Bacillus thuringiensis subsp. aizawai (e.g., XenTari). These products can help control caterpillars while conserving beneficials that can help keep pests in check.

Entrust (active ingredient spinosad) is also effective for caterpillars and may suppress flea beetles. Pyganic (active ingredient pyrethrins) may also help provide protection against flea beetles and some caterpillars. In areas where there is confirmed resistance of diamondback moth to products with Bacillus thuringiensis subsp. kurstaki or spinosad, consider applying products like Xentari, which are produced from a different strain of bacteria (Bacillus thuringiensis subsp. aizawai). Row covers can be very effective for excluding these pests when temperatures allow their use. For example, flea beetles are typically worse early in the season when temperatures are cool, and row covers may be helpful at this time.

For cucurbits and all vegetable crops, ask the owner of the land you may rent what herbicides were applied the year before. Herbicides used in some field crops can carry over to cause crop injury. Problems can be avoided with good communication. MSU Extension’s field crops herbicide guide has a table showing rotational restrictions for select vegetables.

Onion growers continue to direct sow pungent yellow onions and transplant onions as soil conditions allow. Onions have emerged and were in the loop stage at one west Michigan location last week.

For sweet corn, a true armyworm trap in Oceana County detected a significant flight last week. Moths can lay eggs on cereals as well as grasses in ditches, field edges and orchard floors. Caterpillars can hatch and feed and then march to seedling corn. Scouting can target fields planted near these areas.

To scout emerging corn, examine five plants at 20 locations. Treatment may be justified if greater than 35 percent of plants are infested. Caterpillars can hide in the whorl during the day, so look closely. Feeding damage is easy to detect as caterpillars take chunks out of leaf edges (see photos below). Organic growers can use Bt products when larvae are small; pyrethroids are effective for conventional control.

Armyworm in whorl Armyworm damage

Consider scouting sweet corn fields near large, grassy areas for true armyworm this spring. Caterpillars can hide in the whorl during the day, so look in the whorl (left). Damage is also easy to detect as leaf feeding along leaf margins (right).

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