In this issue:
Corn Earworm Migration Continues
CEW - Frequently Asked Questions
| Vol. 1 No. 3 | September 2, 1999 |
Corn Earworm - Frequent Questions and Alternative Control
For growers looking at alternatives to conventional insecticides, there are a few options to consider. However, CEW is one of the most damaging insect pests of sweet corn. All of the following must be evaluated carefully, and initially attempted on small sections of your farm, for efficacy and feasibility.
Control options:
Biological Control: There are some parasitic wasps (Trichogramma pretiosum) that attack (parasitize) CEW eggs, but multiple releases are needed (every 3-4 days) during the silking period, to continue to parasitize eggs, as new eggs are laid. If you have a good supplier of wasps (i.e., timely delivery and high quality), this can be possible for small acreage plantings. You have to consider the cost and labor.
To contact some of the leading
biological control companies, those who are members of the Association of
Natural Bio-Control Producers, see:
http://www.biohaven.com/cgi-bin/cgiwrap/biohaven/sites/anbp/alpha.pl
Other related Bio-Control Resources, are located on VegEdge at:
http://www3.extension.umn.edu/vegipm/intro/ipmother.htm
Pyrethrum Insecticides: The pyrethroids as a group, are relatively safer than some of the older organophosphate materials (e.g., lower oral toxicity), to farm workers (i.e., dermal or oral exposure). They have excellent residual activity, yet dissipate within reasonable period before harvest. Thus, they have minimal pre-harvest intervals of 1-2 days (see specific labels). Their primary drawback is a high toxicity to aquatic organisms; thus, they have limitations to how close they can be applied to streams, lakes, etc. For many production fields, however, this is not a major limitation.
Pyrethroids were initially developed (20+ years ago) from the pyrethrum chemistry of Chrysanthemum flowers (Kenya). Various "pyrethrins" are still available from organic suppliers, and are organic-certified by most groups. The organic-certified pyrethrins have good initial activity, but do not have the same residual activity as the more recent "commercial" pyrethroids. Nevertheless, 2-3 pyrethrin sprays from early to peak silk will provide some protection against CEW. Pyrethrin can also be tank-mixed with one of the foliar Bt products for added control.
Bt Products: Bacillus thuringiensis (Bt) formulations, developed from the common soil-borne bacterium, such as Dipel or MVP, have been available for sometime. Dipel ES or 2X, are effective on European corn borer. Although less effective on CEW, they can provide some control, especially under low to moderate pressure. MVP is encapsulated to give it longer residual activity. However, as a genetically engineered product, it may not be approved by organic certification agencies. Dipel is a "traditional" formulation (spores and crystals) that is still approved by most organic groups.
We have evaluated both Dipel and MVP using aerial applications in a two year study, for processing sweet corn. (email Bill Hutchison, if you want a copy of the journal article, to: hutch002@tc.umn.edu).
Co-Editors: Bill Hutchison, Department of Entomology,
University of Minnesota
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture
Production Editor: Rebecca Hines, Research Associate, University of
Minnesota
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 November 11,
1999.
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