West central Michigan small fruit update – June 30, 2020

Strawberry harvest is almost complete. Harvest of early blueberry varieties started this week in Allegan and Van Buren counties. Some high tunnel produced raspberries are also harvested, and summer raspberries will start soon.

Blueberry showing pH problems
Blueberry (Duke) showing pH problems associated with high pH in the ground and irrigation water. Photo by Carlos Garcia, MSU Extension.

For the past seven days, weather conditions remained unchanged. Daily maximum temperatures averaged 81 degrees Fahrenheit and daily minimum temperatures averaged 60 F. In addition, not much precipitation accumulated during the same period. There was one single rain event during the past week that left a little more than 1 inch of rain in the area. Lack of sustained rain is already creating a water deficit in west central Michigan and growers are providing supplementary irrigation to maintain fruit quality in all small fruit crops, including blueberries, strawberries and raspberries. The weather forecast for the next seven day does not looks promising either. According to Michigan State University Enviroweather, the probability of rain for the next seven days is less than 30%.

Because of these periods of limited precipitation or not precipitation at all, irrigation has been required for long periods of time. In fields with high pH problems, especially in blueberries, prolonged irrigation periods with water with high pH (7.5 or greater) is already changing the pH of the soil, and its effect is shown by the new growth (see photo). Adjust the water pH and apply elemental sulfur to the ground as soon as harvest is complete.

Blueberries for fresh market are harvested in southern counties, Allegan and Van Buren. At this time, the first pick of Weymouth and Duke blueberries just started. Despite late spring frost damage to some early season varieties, fruit quality is excellent.

Growers are not reporting major problems in blueberries. However, our regional weekly spotted wing Drosophila (SWD) monitoring program indicates a substantial increase in the number of SWD flies captured in our trap network. Be alert to the SWD presence in Allegan County, especially in fields next to woods or places with wild plants that are recognized hosts for SWD.

If insecticide applications are needed, make sure you select the right insecticide. Keep in mind that the best management alternatives for keeping a good control of SWD is attacking the pest as soon as it arrives in the crop. Do not wait too long. One single female SWD is capable to lay up to 300 eggs. Left uncontrolled at the beginning of the arrival, it will make it very difficult to maintain a good control during the resto of the harvest season.

At this time and given the current weather conditions, the best alternatives are Lannate, Brigade, Imidan, Danitol and Entrust, among others. Control should be directed mainly to eliminated adults, eggs and the first generation of larvae that may be already hatching in the fruit. For other recommended products and doses, please check the 2020 Michigan Fruit Management Guide (MSU Extension Bulletin E154). You may also call your local MSU Extension office for assistance.

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