West Central Michigan small fruit regional report – July 1, 2014
Strawberry harvest is coming to end, but will proceed another week in the region’s northern counties. Spotted wing Drosophila continues showing up in traps in southwest and Ottawa County strawberries, but no damage has been observed.
Weather conditions in West Central Michigan continues being hot and humid. The daily maximum temperature for the past seven days, as of July 1, has been 81 degrees Fahrenheit, and the minimum temperature has been 64 F. As of July 1, the growing degree day (GDD) accumulation since March 1 is approximately 950 GDD base 50 F.
Although strawberry harvest was abundant, rains occurring during the past week caused problems related to fruit rots, mainly Botrytis gray mold. That caused serious losses in some fields where strawberries ripened very fast and growers were unable to harvest in those particular days. At the same time, the rain prevented growers from having a good fruit rot control. Some growers also reported failures in gray mold control despite multiple applications of fungicides. If you had problems controlling gray mold, contact Michigan State University Extension plant pathologist Annemiek Schilder at firstname.lastname@example.org. She is trying to collect fruits with gray mold that can be analyzed for fungicide resistance.
Blueberry harvest of early season varieties will start this week in Southwest Michigan. However, the main varieties are still one or two weeks away from beginning harvest. Fruit is of good quality, but yields might be lower than the ones observed in 2013. Currently, disease and insect problems in blueberries are minimal, a few cases of Phomopsis cankers and little fruit worm damage. The fruitworm season ended with a minimal impact on blueberry production. Both cherry fruitworms and cranberry fruitworms seemed to be seriously impacted by the winter and their populations were very low and in some case non-existent at all.
Contrary to fruitworms, spotted wing Drosophila (SWD) are already showing up in Southwest and Central Michigan, although still at low population levels. The past week we started observing in the SWD traps some Drosophila species that resemble SWD. However, they are not. It is especially difficult to separate the females from the real SWD, but a close examination of the ovipositor will reveal the difference. Also, the dark band pattern on the female abdomen is different. SWD has continuous dark bands and the “impostors” show broken dark bands as the ones shown in the picture. It is important that growers and consultants identify this difference before recommending any pesticide application.
On the other hand, if SWD is already in your field and your berries are still one week or more away from harvest, you may start SWD control using Lannate at the recommended dose (see the 2014 Michigan Fruit Management Guide, E-154). Save the pyrethroids for applications during harvest so you may reduce the exposure of SWD to this type of insecticides to prevent pesticide resistance.