Southwest Michigan vegetable update – Sept. 6, 2017

Cool temperatures cause economic doubt for late vegetable plantings.

Tomatoes showing “gold flecking” thought to be associated with thrips feeding. Photo by Ron Goldy, MSU Extension.

Tomatoes showing “gold flecking” thought to be associated with thrips feeding. Photo by Ron Goldy, MSU Extension.

Weather

Temperatures were below normal with highs from 66 to 84 degrees Fahrenheit and lows from 42 to 58 F. Michigan State University Extension reports we continue to fall behind in growing degree-days (GDD). We are approximately 478 behind 2016 and 184 units behind the five-year base 50 average. We received approximately 0.5 inch of rain for the week and 1.75 inches for the past six weeks. Unirrigated crops and other plants show signs of stress.

Field activity

Growers are beginning the plastic removal process by splitting it down the middle. So far, I have not seen any plastic actually being removed but that will start soon since harvest activity is beginning to slow.

Crop Reports

Harvesting continues on all crops. However, total volume is dropping as growers abandon older plantings and cooler temperatures slow maturity. Mite damage is noticeable on many tomato plantings. Doing anything this late in the season for control is questionable. Bacterial issues have also taken their toll on many tomato plantings.

The normal high temperature for this time of year is 79 F at the beginning and 70 F at the end of the month. Average low is 58 F to 48 F from beginning to end. We are experiencing end of the month temperatures at the beginning of the month, and the long-range forecast predicts below normal temperatures for much of the month. Late-planted fields of many crops may have trouble maturing fruit under these conditions.

A condition tomato growers may experience is a “gold flecking” on the tomato fruit (see photo). Causes for this are not totally known. What is known, is that thrips populations are higher on those plants that have more severe symptoms. Therefore, by association it is thought the condition is due to thrips feeding. This makes sense given the flecking pattern. The flecks often surround a red center as seen on some of the fruit in photo. The center is where two fruit touched and the thrips could not feed. The flecking can also be concentrated on areas under the leaves. This is an area where thrips congregate since they may feel safer. The gold flecking on the red background would actually be an attractive contrast if the flecks were uniformly spread.

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