During the past week, the fruit growing areas of West Michigan have experienced variable weather conditions that included days with daily maximum temperatures in the upper 70s and in the upper 50s. Nighttime temperatures for the most part have remained above freezing, but in some locations minimum temperatures have dropped below freezing. However, no damage has been reported to any small fruit crop.

Despite the changes in the weather conditions, the current growing degree day (GDD) accumulation since Jan. 1, 2014, in West Central Michigan goes from 497 GDD base 40 degrees Fahrenheit to 193 GDD base 50 F. For the purpose of insect pest phenology, GDD accumulation since March 1 is 193 base 50 F. That is a little change in GDD accumulation that is causing a two-week delay in the physiological development of plants and insects.

So far, the most advanced phenology development has been observed in strawberries. In Ottawa County and north, day-neutral strawberries are in full bloom. On the other hand, early season varieties just started blooming. Currently no disease or insect problems have been detected.

For blueberries, most varieties are in bloom with different percentages of open flowers. In Allegan County, early season varieties are at 50 percent bloom and middle season varieties are between 10-20 percent bloom. There were some nights with temperatures below freezing, but for only one or two hours with no effect on flower buds.

Regarding insect pest problems in blueberries, cherry fruitworms started emerging the past week around 180 GDD base 50 F accumulated since March 1. We believe this early flush of adults coming of diapause will not be a problem since no fruit is available for oviposition. However, early season varieties will be affected as soon as the first petal fall occurs. Michigan State University Extension recommends keeping a close eye on the population dynamics of cherry fruitworm and fruit development to prevent an early attack by this pest.

Before applying any insecticide against fruitworms, make sure there are fruits that need to be protected. Normally, that happens at the first indications of the beginning of petal fall. Please keep in mind that some of the insecticides used against fruitworms are restricted products that cannot be used in areas inhabited by endangered species.

Read the label to make sure you are in compliance with the recommended guidelines. For the most updated insecticides and doses for fruitworm control, please consult the 2014 Michigan Fruit Management Guide (E-154). You may also contact Carlos Garcia at 616-260-0671 or garcias4@msu.edu.