West central Michigan vegetable regional report – June 29, 2016

Insect pest activity is continuing in west Michigan vegetables.

A rust aeciospore lesion present at the base of asparagus fern. Photo: Ben Werling, MSU Extension.

A rust aeciospore lesion present at the base of asparagus fern. Photo: Ben Werling, MSU Extension.

Asparagus harvest is now complete, with harvest ending last Friday, June 24, at the latest-harvesting farms I visited. First cover sprays of fungicides were being applied to young plantings at some farms this week. Japanese beetles were present in low numbers in research plots this week. Tarnished plant bugs were also active. Rust aeciospore lesions were visible on asparagus in research plots that were let go to fern. Check the base of young plants for these lesions. Applying tebuconazole now to fields with current or past aeciospore lesions can reduce production of uredospores later in the summer, which reproduce much more quickly and can be damaging.

Cucurbit growers that started a weekly, copper intensive program for controlling angular leaf spot after plants had true leaves can now scout fields for symptoms of this disease. If symptoms are present, consider sending a sample to Michigan State University Diagnostic Services. If the lab confirms presence of the pathogen, consider continuing a copper-intensive program. If you find no evidence of a problem, consider discontinuing a copper intensive program. Thankfully, conditions have not been conducive to major spread of this pathogen. Note that there are a variety of foliar diseases of cucurbits, and leaf injury can also be caused by many things besides disease.

Cole crop growers should continue to be on the lookout for cole crop caterpillars and treat as necessary. Learn more about these pests and thresholds for treatment in “Caterpillar Pests in Cole Crops” by MSU Extension. There are a wide variety of insecticide options available for conventional and organic growers. Organic products include Bacillus thuringiensis var. kurstakii and spinosad (e.g., Entrust). Bt products include Agree, Javelin, Dipel, Bio bit and XenTari. Products can be applied based on thresholds.

In onions, thrips continued to be present in fields I visited last week. At this point in the season, if you are past the period for using Movento, you could apply Agri-Mek or Lannate based on a one thrips per leaf threshold. Radiant should be conserved for later in the season or if thrips populations are rapidly increasing and are out of control, and can be applied based on a threshold of three thrips per leaf.

In peppers, aphids and their natural enemies were present in fields I visited this week. Aphid problems are most critical when populations increase after fruit set, as honeydew from aphid colonies can coat peppers and promote growth of sooty mold. Treatments can be made based on scouting and thresholds. To scout, you can count aphids on the underside of two lower and upper leaves on five plants in five locations and average numbers across the 100 leaves you count.

Thresholds for applying insecticides to peppers for aphid control, from the “Northeast Pepper IPM Manual.”



Prior to fruit set

Treat if aphid populations are greater than or equal to five per leaf for two weeks.

After fruit set

Treat immediately if aphid populations are greater than or equal to five per leaf.

For potatoes and tomatoes, dry weather is producing a low risk of late blight development for the entire period of June 29-July 3 at west Michigan MSU Enviro-weather stations. To date, the most northerly report of late blight from the eastern US on USA Blight was from Maryland tomatoes.

For sweet corn, Insect Forecast suggests we have not had conditions conducive to flights of corn earworm into Michigan over the past week.

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