MN Fruit & Vegetable IPM News - Vol. 4, No. 7

Over the past week in Rosemount, MN (Dakota Co.), we have had treatable populations of all the key insect pests in the major vegetable crops that we monitor. To avoid significant crop injury or yield loss in the coming weeks, we want to emphasize the importance of regular and frequent scouting trips to the field. Cabbage looper (CL) levels have exceeded 20% plants infested with larvae (threshold = 10% plants infested with larvae) in the past week. Potato leafhopper (PLH) populations have exceeded the 1.0 PLH per sweep threshold in flowering snap beans and were as high as 3.0 PLH per sweep in alfalfa with a maturing nymph population. The presence of nymphs that are approaching the adult stage indicates that populations can rapidly increase as new migrants into the state join the new adult PLH emerging from alfalfa and other crops. European corn borer (ECB) trap catches have remained relatively low across the state; however, there have been hotspots (see graph, below) in southern Minnesota. If your snap beans are at blossom and corn borer black light trap catches are greater than 10 per night, treatment is likely warranted. Striped cucumber beetle (SCB) populations exceeded 1.0 SCB per plant in cucumber at the flower stage. If the defoliation threshold of 25%, for plants with >4 true leaves, is not exceeded then attention should turn to any plants that are wilting. Causes of the wilting could include squash bug feeding, draught stress, and bacterial wilt. If squash bug feeding and draught stress can be ruled out and bacterial wilt is suspected, the wilting plants should be removed from the field to prevent any further spread of bacterial wilt.

Sweet Corn

European corn borer (ECB) trap catches have been low for most of the state this past week (http://www.vegedge.umn.edu/2007/MNlist.htm). One exception was the blacklight trap in St. James (Watonwan Co.) with a one night trap catch of 228 on June 21^st followed by catches of 58 and 46 per night on June 22nd and 23^rd, respectively (see graph, below). This trap catch likely reflects the peak emergence of the univoltine strain of ECB which should occur at approximately 1078 degree days (base temperature of 50° F). As early planted sweet corn is approaching the tassel and silk stages, univoltine moths could pose a potential threat for significant egg lay on sweet con in susceptible growth stages. Corn earworm (CEW) trap catches have remained low in wire mesh pheromone traps across southern MN with the highest one night catch of 9 moths. The progress of CEW trap catch can be viewed on the VegEdge website at http://www.vegedge.umn.edu/2007/CEW.htm

Female (left) and Male (right) ECB Moths (Eric Burkness, Univ. of MN)

ECB graph

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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 June, 2007 by woldx018@umn.edu
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