East Michigan vegetable regional report – July 22, 2015

It’s been a fantastic week for growing vegetables in the Bay area.

Zucchini yellow mosaic virus symptoms shown here include constricted and stringy leaves, twisted and lumpy young fruit and unaffected older fruit, which set before aphids transferred the virus.
Zucchini yellow mosaic virus symptoms shown here include constricted and stringy leaves, twisted and lumpy young fruit and unaffected older fruit, which set before aphids transferred the virus.


Conditions are ideal for vegetable production right now. Growers in the Bay area have started to irrigate some fields.

Here are the rainfall and growing degree day (GDD) base 50 degrees Fahrenheit accumulations to date from Michigan State University Enviro-weather stations.

Rainfall and GDD summary


GDD (50 F, March 1)

Rainfall (inches, April 1)


1216 (192.3 behind average)

8.78 (0.12 since last week)


1308 (213.5 behind average)

8.64 (0.37 since last week)


1307 (198.7 behind average)

12.55 (1.17 since last week)


1347 (148.8 behind average)

12.37 (0.92 since last week)


Sweet corn harvest is underway in eastern Michigan. Pest pressure has been low, but I am distributing corn earworm traps to growers in my region. Corn earworm moths blow in from the southwest, so one way to determine the source population is to look at the excellent trapping network maintained by Purdue University. LaPorte, Whitley and Tippecanoe counties are closest to Michigan.

The first 10 percent of pickling cucumbers were harvested with above average yields in the marketable sizes, and this week more nubs showed up at the sorting stations, probably due to poor pollination. I also observed a wagon of bees in a cucumber field with only five true leaves yesterday, July 21. Putting the bees in your field that early can effect foraging efficiency in your crop. Honey bees perform an orientation flight when their hives are moved. If no cucumbers are flowering for the first 48 hours, then the bees will lock on to other flowers in the area. They will slowly work their way back into cucumbers when they start to flower, and the result may be uneven fruit set, crooks and nubs. If possible, hold off on moving bee wagons into cucumbers until green flower at the earliest, but preferably when male flowers start showing up. This way, when honey bees do their orientation flights, they are met with a field of flowers right at their doorstep.

I haven’t found downy mildew in Saginaw or Bay counties, and hope that Michigan State University Extension recommendations for controlling downy mildew are helping on that front. Downy mildew in melons and cucumbers was confirmed in Berrien County this week.

Melons are just starting to be picked. Fusarium wilt symptoms are showing up in watermelons. This wilt is very specific to watermelons, so other crops in your rotation will not exhibit wilting symptoms from this species. Fortunately, breeding programs have been directed to combat this pathogen. Seedless varieties with good partial resistance include Distinction, Fascintation, Matrix, Melody, Triple Threat and Vagabond. Pollenizer varieties include Companion, Sidekick, SP-5 and Regency (also edible). In addition to using resistance varieties, growers should also strive to work with a six-year rotation before watermelon gets back to the same ground.

Zucchini and summer squash are continually harvested. Zucchini yellow mosaic virus is showing up in some fields. This is transferred by aphids and will only affect fruit that have set after the aphids transferred the virus. On the same plant you can have lumpy fruit and regular fruit, and can determine when the aphids came through. Sometimes they move on and sometimes they have just enough time to transmit the virus before a cucumber beetle spray takes them out too.

Cole crops in some regions are exhibiting symptoms of blindness. This is a strange physiological issue. When the cells at the tip of the main shoot of cole crops differentiate into reproductive tissue (curds or heads), they cannot revert back to vegetative cells. So, if the growing point is damaged somehow once it has turned reproductive, then the plant will not produce a curd or head. It can be damaged through hard prolonged freezes, cutworm damage, low light levels (in broccoli) and over- or under-watering in transplant trays. Have you ever seen pepper and tomato transplants flowering in the greenhouse? They do that when they are stressed. Those plants can bounce back to vegetative mode once they are transplanted and still produce additional fruit. However, yield will be reduced.

In cole crops, the growing tip cannot bounce back to vegetative mode, and every part of the plant below that tip will start twisting and growing more laterally than vertically, making them look “blind” and “without direction.” They don’t know what they are growing for anymore. Their reproductive tissue stalled out, but all other environmental conditions are telling them to grow.

Field tomatoes and peppers are being harvested. Early blight is showing up in many operations, and many fungicides work well for this problem. Some fields with bacterial issues early on are making a great come back, though they are delayed in ripening.

Large candy onions are being harvested and some short-day cooking onions too.

Please contact me at phill406@msu.edu or 989-758-2502 to pick up any suspected disease samples, or send the diseased plant parts to MSU Diagnostic Services.

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