MN Fruit & Vegetable IPM News - Vol. 4, No. 1

The berry plants are starting to grow and leaf out with the recent warm weather. For some berry growers, the joy of seeing new leaves has been tempered by the realization that there is winter injury in their fields. Although the winter of 2006-2007 was warmer than average, the February cold snap was severe enough to damage berry plants. Winter injury can be confused with nutrient deficiencies, insect damage or diseases, depending on the crop and the time of winter when the injury occurred.

Tip dieback on ‘Royalty’ Raspberries

In raspberries, the canes die back. Sometimes, the top three inches of a cane die. In other cases, canes die back almost to the ground. Mild winter injury in raspberries rarely lowers yields, because healthy buds at the base of the canes grow into small branches and compensate for the tips that died back. You can prune the dead wood out of the raspberries in early May.

The tips of many blueberries died, but blueberries have a different growth habit than raspberries. In raspberries, flower and fruit buds are found in the same bud, and the flowers emerge long after the plants leaf out. Blueberries have distinct floral and leaf buds. Floral buds are larger than leaf buds and swell earlier in the spring. Blueberry floral buds are found at the tips of the branches, so if a blueberry branch dies at the tip, some of the crop can be lost. The floral buds may die from winter injury, while nearby vegetative buds are healthy. You should cut the dead branches out of the blueberries, but wait until after bloom, because there are usually more living branches than you think when you first notice dead branches in April.

Both raspberries and blueberries planted near wind breaks had less winter injury than plants exposed to the north and west winds.

Flower in a strawberry with winter injury
The fruit will be small because there are
No leaves to support the fruit.

In strawberries, the middle of the crown is more susceptible to winter injury than the leaf and flower buds at the tips of the crown. In the most severe winter injury, the entire crown dies, but this year we are seeing a lot of intermediate winter injury. The leaves sprout, but remain stunted because the crown can no longer support a full sized leaf. Sometimes the damaged crowns bloom and make fruit the size of small peas. Many of the flowers opening the second week of May are from damaged crowns. If you suspect that a field has severe winter injury, start making plans to remove the field later n the growing season or put in extra plants this spring.

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ACKNOWLEDGEMENTS

Co-Editors: Bill Hutchison (hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness (woldx018@umn.edu), Department of Entomology, University of Minnesota

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN). Reports are posted on the U of MN and MDA web sites on Fridays. If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jeanne Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us , MDA, 625 Robert St. North, St. Paul, MN 55155. You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: www.mda.state.mn.us/plants/pestmanagement/ipm/ipmnews.htm

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture – Risk Management Agency (RMA). These institutions are equal opportunity providers.

DISCLAIMER

Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current manufacturer directions.

Last Revised May, 2007 by woldx018@umn.edu
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