West central Michigan small fruit regional report – May 5, 2015

Small fruit crops in west central Michigan are developing rapidly after a long period of low temperatures that kept crops dormant for at least two more weeks than last year.

Current temperatures are back to the normal temperatures typical of early spring. During the past 10 days, daily temperatures started climbing into the upper 60s, promoting better conditions for plant development. During this period, maximum daily temperatures have been on average 64 degrees Fahrenheit with an average minimum of 38 F. So far, only short periods of freezing temperatures were observed in the area April 26 and 28 when minimum temperatures were around 29-31 F. This did not cause a problem for blueberries or strawberries, the two crops that are in active development at this time.

Blueberries are developing fast thanks to high temperatures from the past week. In Allegan County, most varieties are in flower bud development ranging from “tight cluster” to “early pink” and “shoot development” stage. In Ottawa County, bud development is four to five days behind in southern counties.

Despite the prevailing good weather, the impact of the harsh winter conditions that occurred in January and February is showing in most blueberry varieties, especially in Allegan and Van Buren counties. Fields have few flower buds, and in varieties like Elliott and some Bluecrop fields, flower buds that are opening are empty. Early in the season we observed between 40-60 percent flower bad damage at those fields. The least affected variety is Jersey, which shows more viable flower buds than any other variety. These conditions may have a substantial impact on the size of the blueberry crop for this season.

In most cases, winter damage affected entire shoots that, in some fields, reached more than half of the plant’s structure. Growers may need to extensively prune damaged canes to promote new growth. Leaving those affected shoots unpruned will not help the plant’s rapid recovery.

In addition to extensive pruning, winter-damaged fields require protection from mummy berry and Phomopsis twig blight and cane cankers. However, we are not seeing mummy berry mushrooms in numbers that may represent a risk of infection around the area. It seems despite the low temperatures that prevailed during the past 10 days, lack of substantial precipitation during this period did not provide enough hours of wetness to create a considerable risk of infection. Weather forecast for the next five days does not seem to favor mummy berry outbreaks either.

In regards to early insect pests, growing degree day (GDD) base 50 F accumulation since March 1 is around 135, and the weather forecast for the next five days predicts a GDD accumulation of 230 by May 11. We are expecting the beginning of overwintered cherry fruitworm emergence within the next few days, especially in southern counties like Allegan and Van Buren counties. Michigan State University Extension recommends placing the pheromone traps to initiate the monitoring of this pest.

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