MN Fruit & Vegetable IPM News - Vol. 1, No. 10

European corn borer (ECB): The 1 st generation of the bivoltine ECB flight should be finished. Any ECB being caught at this time of year should be univoltine moths, including the low levels of ECB that we continue to catch at Rosemount, MN (see graph below). Other areas (Gaylord) are also catching ECB, but fortunately, at relatively low levels. Based on recent years at Rosemount, if the univoltine flight continues at >20 moths/night, for several nights, there is a good possibility of egg-lay on tasseling or silking corn (i.e., >4% of plants with egg masses). These infestations can clearly result in significant ear infestations. We will continue to monitor these flights.

Corn earworm (CEW): As per “normal CEW years,” we continue to see very low CEW trap catches across the state. For additional information see the 2004 Moth Flight site for up-to-date information on moth flights. By viewing the moth flight page, you will see that in most years, the CEW flight does not really begin to increase until late July or early August, for most southern locations.

Potato Leafhopper (PLH): In snap beans, adult PLH/sweep in maturing snap beans range from 0.5-1.5/sweep. However, nymph counts are as high as 50 nymphs/30 leaflets. In late-planted snap beans (unifoliate-1 st trifoliate stage), nymph populations have not developed yet, but adult counts range from 0.5-1.5/sweep, which exceeds treatment thresholds. Damage symptoms are present in all snap bean plantings, with older plantings exhibiting leaf puckering and curling (see image, below left), and younger plantings exhibiting necrotic lesions on leaves. In alfalfa, adult PLH counts are low (0.25/sweep). However, nymph populations have started to increase, which may represent a decline in the 1 st generation adults. The second generation of adults should start to appear within the next two weeks.

Cabbage looper (CL): Trap catches remain low at Rosemount. After an initial infestation of cabbage fields (25% plants infested), larval populations appear to be declining. In the absence of additional moths migrating into Minnesota, larval populations should remain low for the next few weeks.

Western Bean Cutworm (WBC): We are beginning to catch a few WBC moths in the Rosemount light trap. Until we have further recommendations for WBC in Minnesota sweet corn, we are recommending an Idaho-based threshold of 2-3% of the plants with WBC egg masses, from tassel through silk. WBC eggs will initially be white in color changing to a distinctive dark purple just before hatching, which is unique from ECB. Fortunately, to date, this species continues to occur at low levels (2002-2003), with the highest moth flights limited to southwestern MN.

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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.

DISCLAIMER

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 July 15, 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.