In this issue:

European Corn Borer Flight Update

Potato Leafhopper and Bean Leaf Beetle Update

Risk Management Publication Available

Pesticide Safety Reminders

Potato Leafhopper and Bean Leaf Beetle Updates

Bill Hutchison, Eric Burkness and Bob Koch, University of Minnesota, St. Paul.

Potato Leafhopper Populations Continue-PLH counts have been high, or building for the past 4 weeks. On July 7th, at Rosemount, PLH adults exceeded 5/sweep in alfalfa; nymphs were too numerous too count. Sampling reminder: at these densities, 3-4 sets of 10 sweeps each, is more than adequate to determine threshold levels and treatment decisions. Numerous recent storms from the south, warm weather including high dew points, have all contributed to immigration of adults, high adult survival and egg-lay.

xx

xx

In snap beans, at Rosemount, we have adult counts of 2-3/sweep, with nymphs in untreated snap bean plots at more than 1 per leaflet of a trifoliate leaf (=10x the threshold). Thresholds for snap beans are:

Seedling Stage (Two true leaves)

• Adults: 0.5 adult PLH per sweep or 2 per row foot
• Nymphs: Nymphs usually not present at seedling stage

3rd Trifoliate to Bud Stage

• Adults: 1 adult PLH per sweep or 5 PLH per row foot
• Nymphs: 1 nymph per leaflet

Snap beans with threshold PLH, that are still more than 7 days from the first pin bean (1=inch) stage (when insecticides are typically applied for ECB) will need to be protected with an additional spray, to minimize yield loss. PLH are relatively easy to control with all insecticides labeled, and with the newer pyrethroids, reduced label rates can be used. However, with some of the pressure we have observed this year, I would not go below ½ the labeled rate, to provide maximum residual control of nymphs. For example, Bruce Potter (U of M-Lamberton) indicated this week, that the 0.10 lb rate for permethrin (Pounce at 4 oz/ac) was only providing residual control for 6 days; for this product one should stay with 0.15 lb AI (6 oz/ac), or up to 0.20 (8 oz/ac), where labeled for a given crop, and if early in the season.

As before, PLH counts continue to be above threshold for most crops. All crops should be watched closely for PLH.

For more information, please see the PLH fact sheet at: http://www.vegedge.umn.edu/vegpest/plh.htm

Bean Leaf Beetle-As of July 9th, we had not yet observed emergence of the next BLB adult population (F1 adults). New adult activity, however, was reported this week by Tom Rabaey (General Mills) in the Le Sueur area, with new feeding occurring on snap beans. F1 adults should be emerging very soon throughout southern Minnesota. Snap beans that are beyond the 2nd or 3rd trifoliate should be able to tolerate BLB feeding; potential pod feeding should be eliminated with the use of foliar sprays for ECB or CEW. A new fact sheet on BLB is available at: http://www.vegedge.umn.edu/vegpest/BLB.htm

Co-Editors: Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Production Editor: Suzanne Wold, Research Fellow, Department of Entomology, University of Minnesota, woldx018@tc.umn.edu

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 directions of the manufacturer

Last Revised August 6, 2003.
The University, including the Minnesota Extension Service, is an equal opportunity educator and employer. ©1999-2003 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.