West central Michigan vegetable regional report – May 29, 2013

Prepare for disease development in asparagus and cucurbits.

Asparagus harvest continued this week with cool weather allowing growers to catch up on harvesting this past weekend. Recent cool, wet conditions are favorable for purple spot, which has been observed in Oceana, Mason and Manistee counties. Conditions are also favorable for development of Phytophthora spear rot, which could develop in fields that have a history of this disease. Asparagus miner is also active with an average of nine flies captured per trap in an Oceana County location this past week. Young, 1- to 2-year-old fields with fern developing will be especially attractive to this pest, which should now be laying eggs.

Purple spot lesion on asparagus
The red arrow points to a purple spot lesion on an asparagus
spear. Purple spot symptoms have developed with recent
cool, wet weather. Photo credit: Ben Werling, MSU Extension

Carrot growers have killed their wheat windbreaks in some Oceana County locations over the past two weeks. Currently, carrots have more than one small true leaves developing in Oceana and Mason county carrot fields.

In Ottawa County, one cucurbit grower had started planting squash as of last week. In Oceana County, this week usually marks the beginning of squash sowing. However, with recent wet weather it may be delayed. Conditions are favorable this planting season for development of early-season problems with Phytophthora capsici in fields that have had a history of this disease. If you are planting into such a field, treatment with Ridomil can provide you with early-season protection against both Phytophthora and Pythium. It can be applied either in-furrow or as a band over the row. Make sure to follow the label as it can be phytotoxic if applied in the wrong place or at the wrong rate.

It is not too early to start being on the lookout for cucurbit downy mildew. Michigan State University’s plant pathologist Mary Hausbeck reported that spore traps in southeast Michigan have captured downy mildew spores, but not at consistently high levels. While downy mildew problems have not become severe until July in recent years, Hausbeck cautioned that disease development has been observed in early June in the past. Keeping an eye out for downy mildew is something that will not only benefit you, but alerting your Michigan State University Extension county educator to its presence can also benefit your neighbors by warning them to the need for protective treatments. Cucurbits growing in low-tunnels that go in early and often are not treated with fungicides are important places to check for early disease development.

Learn more about cucurbit downy mildew by reading MSU Extension’s “Monitoring and Managing Cucurbit Downy Mildew.”

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