MN Fruit & Vegetable IPM News - Vol. 4, No. 2

Strawberries started blooming this past week. Early cultivars like Annapolis are already at 10% bloom in most fields in the southern half of Minnesota. Jewel and Glooscap will start blooming this week. Blueberries started blooming before strawberries and are past full bloom in southern Minnesota.

Clipper weevils appear to be common in strawberries this year, showing up in many fields for the first time. The best way to monitor clipper weevils is to look for holes in the petals of the strawberry blossom and check for clipped buds below the blossoms. Female clipper weevils feed on strawberry flowers and then lay their eggs on the buds below the flower.

Folded leaf with older leafroller

Other insects eat holes in strawberry petals, including strawberry leafrollers. During the week of May 14, strawberry leafrollers showed up in many strawberry fields. Leafrollers are small caterpillars that feed on leaves and anything near the leaves. In strawberries, leafrollers fold leaflets along the midrib with silk (right) or glue several leaves together with silk. To monitor leafrollers, open the leaves and check the age of the caterpillar inside. When leafrollers feed on leaves later in the growing season, the economic threshold is reached when 30% of the leaves have leafrollers. Before bloom, leafrollers feed on flowers and flower buds. There are no established thresholds for strawberry leafroller in spring, but there are enough insects in some fields to worry many strawberry growers.

Young leafroller on strawberry
leaf. Leafrollers should be
controlled at this early stage.

Controlling Strawberry Leafroller: The strawberry leafroller population is usually kept in low by many different natural predators and parasitoids. Mowing at renovation disrupts their life cycle and can reduce the population. For chemical control, any spray used for clipper weevils will also control leafrollers. Soft insecticides for leafroller include Bacillus thuringiensis (BT) insecticides such as Dipel or Javelin.
Always control leafrollers when the larvae are small, before they roll the leaves. Larger leafrollers are hidden in the leaves, where most pesticides cannot reach. BT sprays are only effective when the larvae are young (picture at right).

Table 1: Pests during the week of May 14
Fields Monitored	Fields at 10% Bloom	Fields with tarnished plant bug nymphs	Fields with Clipper	Fields with Leafroller
15	5	1	5	10

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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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