Southwest Michigan vegetable regional report – August 17, 2016

The rain was much needed, but will delay field activities.

Field activity

The area received between 3 and 6 inches of rain Aug. 15 and 16. Field activities were disrupted on Aug. 16 and possibly longer depending on soil type. Some crops where timing is critical for optimum harvest stage, such as yellow squash, zucchini, snap beans and pickles, may have been affected. Fruit will be too large, causing a significant amount of discards or complete fields having to be bypassed, depending on how quickly harvest equipment could be moved in.

Crops

Vine crop growers should continue applying protection for downy mildew. Spore counts at the Southwest Michigan Research and Extension Center remain high and the cloudy, wet conditions on Aug. 16 were conducive for spread. Protection should be applied to all vine crops. Protection should also continue for powdery mildew.

Maintaining a good leaf canopy will be critical for sunburn protection. If the fruit is mature and leaves start to collapse and expose fruit, Michigan State University Extension suggests it would be best to harvest it and place it under protection. Otherwise, the fruit is subject to sunburn and will not hold up under storage.

Late afternoon leaf wilting has been noticed on many plantings. This is due to water loss being greater than water uptake. Plants generally recover overnight and look good the next morning. If they are still wilted in the morning, the cause needs to be investigated. Continued wilting indicates a root or stem issue that reduces the plant’s ability to take up and move water.

Mite infestations have been found on watermelon. These should be controlled since they will also cause defoliation and sunburn. Virus symptoms are present, but not to a great extent. Squash bug numbers remain low.

Bacterial diseases are increasing in some tomato fields.

Common blight (Xanthomonas phaseoli) has been found in snap beans.

Rust has been found in some sweet corn fields. Applying control depends on the harvest date. Generally, infection occurs late enough in the life of the planting that harvest will occur before significant yield losses.

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