In this Issue:
VEGETABLE NEWS
Vegetable Insect Pest Update
A RISK MANAGEMENT AGENCY FACT SHEET
APPLE NEWS
STRAWBERRY NEWS
White Grubs in Blueberries and Strawberries
Please Note: the next newsletter will be published August 11.
| Vol 3 No. 9 | July 21, 2006 |
Vegetable Insect Pest Update
Eric Burkness, Department of Entomology, University of Minnesota, St. Paul
Cabbage looper (CL) adults have finally arrived in Minnesota and have been laying eggs. With the recent heat, late planted cabbage (7-10 leaves) in the Rosemount, MN area had CL infestations of approximately 15% of the plants infested with at least one CL larva. The treatment threshold is 10% of plants infested with at least one CL larva. As the high temperatures continue, monitoring should intensify because the growth rate of larvae will increase as the temperature increases. We always recommend targeting small larvae when possible to increase overall efficacy of insecticide treatments.
Potato leafhopper (PLH) populations in alfalfa have started to increase and are likely a combination of continued adult migration into the state as well as nymphs molting into adults. Sweeps in 6 inch tall re-growth in Rosemount indicated a population of 2.15 adults per sweep well above the 0.5 adults per seep threshold for 6 inch tall alfalfa. In addition to high adult numbers, the continued presence of nymphs in the alfalfa indicates that adult populations could increase in the next 2-3 weeks. Late planted snap beans should be monitored closely as it is a highly attractive host for PLH and as PLH populations increase they will likely move to other crops.
Corn earworm (CEW) pheromone and black light trap catch in most areas of the state continues to remain low. European corn borer (ECB) trap catch should begin to increase in the next week as the start of the 2nd generation of the bivoltine strain of ECB has begun. Through July 17th, degree days for ECB are at 1397 (base 50°F) indicating that the 2nd generation of ECB is starting. The 2nd generation ECB moths should begin flying at approximately 1400 degree days. Egg lay begins at 1450 degree days and therefore, should be underway as well. If the recent high temperatures continue though July, you can expect the developmental times for ECB egg hatch and larval development to be shortened. The period from egg lay to egg hatch is approximately 100 degree days and with recent temperatures 100 degree days could accumulate in as few as 3 days.
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Western Bean Cutworm (WBC) activity continues to increase in the Rosemount area. Blacklight trap catches have remained at 40 moths per night from 7/14 to 7/17. This level of moth catch is the highest moth catch in Rosemount since trapping began in 2002. WBC eggs are laid in clusters of about 50 eggs on the upper-side of the leaf near the mid-rib. Initially eggs are white and develop a darker purplish color as they mature and approach hatching. Eggs hatch in approximately 7-10 days and larvae can feed on tassels in the whorl and then move to the silk and ears in sweet corn. 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. For more information about WBC, please visit the University of Illinois fact sheet (http://www.ipm.uiuc.edu/vegetables/insects/western_bean_cutworm/). |
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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 Jean Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us, MDA, 625 Robert St. North, St. Paul, MN 55155-2538. 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: http://www.mda.state.mn.us/ipm/ipmnews/
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.
The University, including the Minnesota Extension Service, is an equal opportunity educator and employer. ©1999-2006 Minnesota Extension Service, University of Minnesota. All rights reserved. Contact copyright@extension.umn.edu for information on reproduction or use of this material.