MN Fruit & Vegetable IPM News - Vol. 4, No. 6

After several weeks of little to no pest activity in cabbage, things are starting to pick up a little. Samples from cabbage in the Rosemount, MN (Dakota Co.) area on June 14^th detected the first cabbage looper (CL) eggs of the season and on June 20th the first CL larvae. Egg lay and hatch have already been high enough to exceed the 10% plants infested treatment threshold for CL, with 20% of plants infested with small CL larvae in a Rosemount cabbage field. Although we typically don’t expect CL moths to arrive in MN until the first week of July, with the multiple weather events that have blown through the state and the continual high winds, it is not surprising that they arrived a little early this year.

Another interesting find was several imported cabbageworm (ICW) eggs. This pest has been all but absent from cabbage over the last 5-7 years and this is the first season we’ve seen a significant number of butterflies in the field in quite a while. Early planted cabbage transplants are heading now and early seeded cabbage has about 10 leaves. For information on thresholds for CL or ICW click the following links (http://www.vegedge.umn.edu/vegpest/colecrop/looper.htm, http://www.vegedge.umn.edu/vegpest/colecrop/cabbworm.htm).

Potato leafhopper (PLH) populations had not increased significantly in any crop in the Rosemount area last week. However, this week populations have increased in both alfalfa and snap beans and were at treatable levels >0.5 PLH per sweep in unifoliate to 3^rd trifoliate growth stage plants. Plantings that had an insecticidal seed treatment and were at the 1^st to 3^rd trifoliate stage were clean. As flowering progresses and pin beans begin to develop consideration should also be given to European corn borer (ECB) trap catches in your area. 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) has finally arrived in a Rosemount cucumber field last week. Plants at the 6-8 true leaf stage had a 0.8 beetle per plant infestation. Later planted cucumbers nearby at the 1st true leaf were at 0.1 beetles per plant. Typically the larger plants at >4 true leaves growth stage can “outgrow” SCB feeding and treatment shouldn’t be considered until plants show 25% defoliation. Plants at earlier growth stages, cotyledon to 1st true leaf, should be treated when populations reach 1 SCB per plant.

European corn borer (ECB) populations have remained low across the state (http://www.vegedge.umn.edu/2007/MNlist.htm). However, trap catches have increased from previous weeks. The peak moth catch in southern MN (Watonwan Co.) this past week was 29 moths per night. Our Rosemount black light trap peaked at 10 moths per night. As mentioned previously, if you have snap bean fields that are at blossom or later, an ECB treatment may be warranted. The Univoltine strain of ECB (one generation/year) starts emerging at 900 Degree-days (50/86). Bruce Potter just noted that this flight is underway for Southwestern (Fulda) MN. For more info on the timing of this flight, and subsequent larval populations, see the July 2006 article by Phil Glogoza (MN Extension Service) in the NWROC IPM News. Corn earworm (CEW) moths continue to be captured in wire mesh pheromone traps across southern MN but trap catches have been very low. The progress of CEW trap catch can also be viewed on the VegEdge website at http://www.vegedge.umn.edu/2007/CEW.htm.

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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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