Central Michigan small fruit report

Quick overview of the impacts of environmental conditions this spring on small fruit in the Allegan and Ottawa County area.

Blueberries are moving along very well and so far early varieties are in bud burst stage. However, plant growth has been delayed because of the daily low temperatures occurring during the past week. So far high temperatures in the Ottawa-Allegan area have been around 50°F and lows around 37°F. Rain has been present with an accumulation of 1 to 1.5 inches. Because of these conditions, degree day accumulation up to April 26 has reached only 137-144 base 42°F, and 49-51 base 50°F.

Winter damage to blueberries has been reported in some fields. We sampled blueberry shoots from 12 fields on two different dates. The first sample was taken on March 14 and the second on April 21 from nine fields in Ottawa County and three fields in Allegan County. Buds were examined with a microscope and damage estimated. We found winter damage in almost every field, but the amount of damage is low between 10-15%. In this case, buds showed one or two dead flowers. However, complete bud kills were observed only in Ottawa County in fields alongside major highways that received salt during the winter. At those fields bud kill reached 100 percent in the first rows facing the road, 37 feet away approximately. Bud kill decreases as we move away from the road, and approximately 100 feet away damage is similar to that observed in fields located far from salted roads.

There are reports of low bud set in some fields that had a heavy fruit load from the previous years. This is a problem that may become more evident as the bloom period progresses. Some of the reasons for low bud set could be related to nutritional problems and heavy loads during the previous years. Therefore, it is important that for the 2011 fertilization program growers take in consideration the size of the crop that was removed in 2010, the target crop for 2011 and the nutritional conditions of the plant.. Use this information together with leaf and soil analysis to estimate the amount of nutrients required for 2011.

Due to the prevailing environmental conditions, low temperatures and light rains, mummy berry may become a major problem for those fields with history of mummy berry. In those fields, the inoculum is already present and the environmental conditions are suitable for the development of the infection. So far, mummy berry nurseries established in several fields in Ottawa and Allegan County indicate the presence of mummy berry apothecia with mushroom cups measuring 1-1.5 mm. It is important that growers start their mummy berry control as soon as the soil conditions allow.

Regarding other small fruits, strawberries are still covered and no activity is observed at this time. Raspberries are at the bud break stage with some fields moving to green leave stage. We expect development to continue normally as daily temperatures warm up. Blackberries, on the other hand, are still dormant.

For insect pests, degree day accumulation for cherry and cranberry fruitworm emergence still is low, less than 50 DD base 50° F.

Other activities conducted by the small fruit program include an IPM scout training conducted in early March for blueberries. The major topic was the Spotted Wing Drosophila. We dedicated a half day for classroom and hands-on lab with growers to get familiar with this new invasive pest. On April 11, we repeated the SWD workshop. A third workshop will be conducted on June 1, 2011. For all participants of the previous two workshops (March and April), field hands-on training will be conducted during the June 1 workshop. We also conducted a one day workshop on Traceability in Fruit Production. Those events have been conducted at the MSU Trevor Nichols Research Complex in Fennville, Michigan. For information on future workshops, please call Carlos García at 616-260-0671 or e-mail garcias4@msu.

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