MN Fruit & Vegetable IPM News - Vol. 1, No. 2

Bean Leaf Beetles (BLB): On May 11, we observed BLB on sticky traps at the Rosemount Experiment Station (Dakota Co.). A nearby field of snap beans that was just emerging at the cotyledon to unifoliate stage did not appear to have any BLB feeding damage. Our first snap bean planting date (May 3 rd) has not yet emerged, but we will begin sampling for BLB as soon as they emerge. In addition, and as we noted for the first time in 2003, early-season BLB may also move to cucurbits (see image), causing significant feeding damage on cotyledons and first true leaves.

For additional information on BLB, see the VegEdge factsheet: http://www.vegedge.umn.edu/vegpest/BLB.htm. For more information on BLB damage to cucurbits, see the June 20 th 2003 MN News article: http://www.vegedge.umn.edu/mnvegnew/vol5/620pest.htm

Seedcorn Maggot (SCM): We have not yet found an infestation of SCM in snap bean plots planted at the Rosemount Agricultural Experiment Station (Dakota Co.). The peak of the first SCM flight occurred on April 28 th (342 degree days, lower threshold=39°F). Seedlings are more susceptible to SCM during a wet, cold spring when seed germination is slowed. We are currently experiencing faster than normal seed germination, therefore we may see little impact from the first flight of SCM.

Besides burrowing into seeds and destroying the germ, SCM can feed on cotyledons and the first true leaves. The first true leaves may have holes or the maggots may completely eat the leaves, resulting in "snakehead" seedlings (see image). In some cases, the feeding damage completely destroys the growing point. Lab experiments indicate that 5 maggots per snap bean seed cause significant damage. For more information, see the VegEdge fact sheet: http://www.vegedge.umn.edu/VEGPEST/seedmag.htm

Collembola (springtails): This week we observed Collembola feeding on cabbage seedlings planted near Rosemount, MN. Len Dobbins, FMC-Indiana, also observed high infestations of springtails feeding on the terminal tissue and leaves (underside) of snap bean seedlings. In addition, reports of springtail feeding on sweet corn (Delaware) and sugarbeets (Michigan) continue to come in. Collembola are very small (.1-1 mm), and "jump" when disturbed. They are referred to as "springtails" because they use their furcula, which is a structure that protrudes from the abdomen (see image), to "spring" themselves through the air. Collembola typically are present in soil, feeding on decaying plant matter, and rarely move to feed upon economically important crops. However, there are a few species that feed on living plants.

Last year we found collembola feeding on squash seedlings (see photo). Hopefully, as in 2003, their feeding will likely subside as the air temperatures increase and as the soil dries out. Currently there are no consistent recommendations for managing Collembola in any of the crops mentioned. In addition, very few insecticides are labelled for springtails. Furadan 15G is labeled for some crops - this likely acts as directly as the springtails contact the insecticide in the soil, as well as systemic activity in young plant tissue. See the new fact sheet on Collembola for more information.

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ACKNOWLEDGEMENTS

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@umn.edu
Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Division,jeanne.ciborowski@state.mn.us
Suzanne Wold-Burkness, Department of Entomology, University of Minnesota, woldx018@umn.edu

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., Tuesday to Jeanne Ciborowski, 651-297-3217, jeanne.ciborowski@state.mn.us , MDA, 90 W. Plato Blvd., St. Paul, MN 55107-2094. 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/biocon/fruitreports/default.htm

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

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References 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 14, 2004.
The University, including the Minnesota Extension Service, is an equal opportunity educator and employer. ©1999-2004 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.