Michigan’s west central region is passing through a drought period with only 1.87 inches of rain for the past 25 days. This drought coincides with the period of fruit development in blueberries and summer raspberries. However, daily temperatures have remained below the 80s for the most part with an average daily minimum temperature of 52 degrees Fahrenheit and a daily maximum of 76 F. Those temperatures somehow are mitigating the impact of drought conditions, making it less extreme.

Currently, blueberries are in harvest with good quality fruit. Early varieties are producing a heavy crop and growers expect a large crop this season. There are some problems with low productivity in some fields that were affected by two years of winter damage. Those fields presented abundant flowers early in the season, but later presented a large “June drop,” and many canes were with fruit but only a few leaves. Some growers misidentified this condition as an effect of some chemical applied during bloom or after bloom. These effects are more visible in blueberry fields with nutritional deficiencies or located in sandy soils. Correcting these problems will take another year, but a good pruning and the correct nutritional program will help to mitigate the situation in the long term.

Regarding pest problems, there have been a few disease problems in blueberries. Phomopsis canker is the most common problem detected so far. Dry conditions have prevented the development of fruit rots, but conditions for a fruit rot outbreak are appropriate as soon as some rains provide the leaf with the wetness necessary for disease development. Sugar accumulation in fruit is already at its peak in early season varieties being harvested. Therefore, growers need to be alert to any symptoms of fruit rots, especially Anthracnose. This is the most common problem in Michigan at harvest time. For fruit rot control at this time, you may use Abound or Pristine. You may also use Switch. For a complete list of recommended products and dosage, consult the “2016 Michigan Fruit Management Guide,” Michigan State University Extension Bulletin E0154, or call your MSU Extension county office for assistance. You may also contact me at 616-260-0671 or garcias4@msu.edu.

So far the presence of spotted wing Drosophila (SWD) in blueberry fields in the central region remains very low but is steadily increasing. Only in raspberries are we observing SWD actively reproducing, and more SWD females of the summer generation have been trapped there. We observed more males flying in blueberries than in other crops.

Growers actively harvesting or ready to harvest should maintain a continuous surveillance of their fields to prevent SWD buildup. Allowing SWD to prosper early in the season will create serious problems for late-season varieties at the same farm. Given the dry conditions prevailing in the area, Imidan or Lannate will be an alternative if harvest is more than three days away. Growers should visit the MSU Enviro-weather website to check for current weather conditions and extended weather forecasts in order to program their insecticide application and prevent SWD control failures that may be due to insecticide inactivation by high temperatures or rain. For a complete list of recommended products and dosage, consult the “2016 Michigan Fruit Management Guide” or call your MSU Extension county office for assistance. You may also contact me at 616-260-0671 or garcias4@msu.edu.