West Central Michigan small fruit regional report – June 3, 2014
Now is the time for pruning winter-damaged shoots and blueberry plants, and biofix the cranberry fruitworm model to forecast the first insecticide application against fruitworms.
Currently, weather conditions in West Michigan have favored the rapid termination of diapause in cherry fruitworms and cranberry fruitworms. At this time, cherry fruitworms are out and the population, according to the Michigan State University Trevor Nichols Research Center trap line, is dropping while cranberry fruitworms started increasing. Current growing degree day (GDD) accumulation in West Central Michigan is approximately 431 GDD base 50 degrees Fahrenheit and 772 GDD base 42 F.
Adult cherry fruitworms started flying two weeks ago, but this segment of the adult population is what we call a “suicide” population, since no fruit was available for larval development. As of June, that is not the case anymore. Early season varieties are already in petal fall and mid- and late-season varieties are in full bloom. According to our predictive models, the first application for cherry fruitworms and cranberry fruitworms should be already in progress. Michigan State University Extension advises growers to 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 that 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 call Carlos Garcia at 616-260-0671 or garcias4@msu.edu
Strawberries in West Central Michigan are approximately two weeks behind in relation to the “normal” harvest time. However, day-neutral strawberries will start harvesting during the course of this week. At this time there is a potential problem related to the two-spotted spider mite. The insect is already present in older fields where populations are increasing rapidly thanks to the prevailing hot weather conditions. Some of the recommended insecticides for two-spotted spider mite control are Savey 50 DF at 3-6 ounces per acre, and Zeal 72 WDG at 2-3 ounces per acre. For other options, please consult the 2014 Michigan Fruit Management Guide (E-154).
We are seeing extensive winter damage in the blueberry varieties Bluecrop and Jersey (see photo). The damage is less evident in other varieties. In fields facing salted roads, the damage is extensive with 100 percent dieback in rows near the road. It is important to prune those shoots and plants that suffered extensive damage.
In a normal year, shoots store nutrients in the cambium. Those nutrients are used by the plant in spring during bud break and until the full foliage is developed. If those shoots are not replenished by the new leaves, blossoms and fruit developing on those shoots will empty all stored nutrients and the shoot will die mid-summer. Therefore, it’s important to remove those canes and shoots, presenting plenty of flowers and fruits but no leaves. It will help the plant to recover sooner.
