News and Notes from the WI Pest Management Update Meeting

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

Soybean Aphid Update

        The information base on soybean aphid is slowly starting to build.  John Wedberg, UW Extension Entomologist, made the following points at the recent Wisconsin Pest Management Update Meeting in Fond du Lac:

·         Once again, late-planted soybeans in 2001 took the brunt of the soybean aphid invasion.

·         Unlike the Asian countries where heavy infestations occur in early vegetative stages, aphids generally didn't move into upper Midwest soybeans until early reproductive stages.

·         Aphid populations in Wisconsin were minor compared to Michigan and parts of Canada.

·         Threat of disease transmission by aphids remains high for BOTH soybeans and snap beans.

·         Spraying too early for aphids provides only short-term control and can lead to even higher subsequent populations (thought to be caused by killing off beneficial predators to the aphid).

·         Although precise threshold levels for spraying have yet to be determined, it's likely to be in the range of thousands per plant.  Scouting procedures will involve only counting aphids on the upper trifoliolate leaves.

·         Spray prior to visible injury symptoms.

·         A number of insecticides have provided adequate control but overall performance ratings vary with time of application and location.

·         More specific treatment recommendations will be formulated once all of the yield data has been analyzed (sometime in January).

New Herbicide Update for 2002

        Several new herbicide options will be available for 2002.  A brief description of each follows.  Contact your ag chemical retailer for more information on use and availability.

Callisto (Syngenta):

This is a pre-emerge or post applied broadleaf herbicide for field and seed corn.  Callisto can be applied to corn up to 30 inches (V8) but labeled weed height is 0-5 inches (2 inch large crabgrass).  It cannot be tank mixed with methylated seed oil,  EC formulations for post applications, and can't be used after Counter or Lorsban insecticide applications.  The rotational restriction for alfalfa and peas is 18 months.  Future label changes may include the use of Callisto on sweet corn although post-emerge applications have shown to cause chlorosis on certain hybrids.

Define (Aventis):

This is a PPI or pre-emerge applied grass herbicide for field and seed corn.  Several tank mix options are available.  Define's active ingredient puts it into the acetamide family of herbicides.  Bareground giant foxtail studies indicate similar residual control as other shoot growth inhibitor herbicides such as Dual II Magnum, Outlook, and Harness.  Rotation restrictions are 12 months or less for most commonly grown crops.

Steadfast (DuPont):

This is a post-applied grass herbicide for corn containing the same active ingredients as Accent (nicosulfuron) and Basis (rimsulfuron).  Steadfast also provides good control of pigweed and smartweed but does not control crabgrass.  It can be applied on corn up to 12 inches (6 collars).  Several tank mix options are available.  Steadfast needs to be applied to corn hybrids with greater than an 88 day R.M.  It also should not be applied to corn treated with an organophosphate insecticide.  Rotation restrictions are not limiting for most crops.

Gauntlet (FMC):

This is a PPI or pre-emerge broadleaf herbicide for soybeans.  Gauntlet is a co-pack of sulfentrazone 75DF and FirstRate.  Recommended rates vary with soil organic matter content.  Do not apply once soybeans begin to crack soil surface.  Current rotation restriction to sweet corn following a Gauntlet application is 18 months.

Valor (Valent):

This is a pre-emerge soybean herbicide for small-seeded broadleaves.  It is weak on velvetleaf, smartweed, and giant ragweed.  Several tank mix options are available.  Do not tank mix with acetamide herbicides (e.g. Dual II Magnum, Outlook, Axiom, etc.).  Like Gauntlet, cannot be applied once soybeans begin to crack soil surface.  Rotation restrictions are not limiting.

Phytophthora Resistance in Soybean

        It's becoming easier to select soybean varieties with broad-spectrum gene resistance to Phytophthora root rot.  The following table compares the number of varieties with Rps 1k gene resistance (recommended for WI growers) in 2000 with offerings from past years.