In this Issue:

FEATURE ARTICLE

Insect Migration Forecast System for the Midwest

VEGETABLE NEWS

Vegetable Insect Pest Update

STRAWBERRY NEWS

Bronzing in Strawberries

APPLE NEWS

Apple Scab Infections

Take Note! Adult Apple Maggot Emergence

Weekly Trap Counts

Order: 2007 Minnesota Vegetable Guide

Insect, Pest Fact Sheets

Bronzing in Strawberries

Thaddeus McCamant, Specialty Crops Management Specialist, Northland Community & Technical College

The strawberry harvest is in full swing over most of the state.  Many growers are reporting high demand in spite of the hot weather, with many fields being picked clean.  The cool weather that started on June 18 will lengthen the season and improve fruit quality.

Thrips damage in Cavendish, 2006	The most common concern during harvest has been bronzing in the strawberries.  During fruit bronzing, the cells on the skin die, preventing the fruit from swelling as it ripens.  As the fruit grows, the skin cracks and seeds stick out of the skin.  There are at least four causes of fruit bronzing in Minnesota: thrips, heat, spray damage, and cyclamen mites.  If possible, try to determine the cause of the bronzing. In 2006, bronzing was a severe problem in southern and western Minnesota.  We are pretty certain that the problem was due to thrips, tiny insects that fed on the flowers.  Flower thrips often made entire fields unmarketable, by either stunting the fruit or giving the fruit a bad flavor.   Flower thrips damaged most varieties.
Bronzing in Glooscap, 2007	In 2007, I am seeing bronzing that may be due to either heat, spray applications or a combination of both.  The bronzing primarily occurs on the sunny side of the fruit, and on the western side of the rows.  The bronzing reduces the size of the fruit by 10-25%, and in most cases, the berries are being picked by U-pick customers.  Bronzing this year is most common in Glooscap, and appears to have started as the berries were turning from green to white in color.  Bronzing may have been aggravated by poor root growth or poor canopy growth.
Cyclamen mite damage in Mesabi	Cyclamen mites have become a severe problem in some fields this year.  Unlike other fruit bronzing, cyclamen mite damage is concentrated in the leaves.  Cyclamen mites feed on the developing leaves inside the crown.  When the leaves emerge from the crown, they are stunted and twisted.  Plants infected with cyclamen mites are rarely more than 6 inches tall.  Cyclamen mites prefer Cavendish, Mesabi and Annapolis, but we have seen severe damage in Glooscap.

Bronzing from sun or thrips is temporary.  Cyclamen mite damage continues to spread throughout the summer.  Currently, there are two options for ridding a field from cyclamen mites.  You can either douse the plants with fungicide at renovation and again in early spring, or you can plow the field under.  Cyclamen mites almost never cause economic losses in fields in their first year of picking.

In many cases, it is difficult to pinpoint the exact cause of the bronzing.  Always look at the youngest leaves to make sure the problem was not caused by cyclamen mites.

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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.

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Last Revised June, 2007 by woldx018@umn.edu
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