SEE Mail Issue 020715 (July 15, 2002)

	Extension Entomology Mail Mike Catangui, Ph.D. Associate Professor & Extension Entomologist
July 15, 2002 (Issue 020715)

Last Updated on Tuesday October 15, 2002.

Soybean Aphids Being Found on SD Soybeans

(Click to enlarge)

Soybean aphids are currently being found in twenty SD counties. Now is a good
time to be scouting our soybean fields. Most of the pictures above were taken last July 5
on a soybean field near White, SD. Terry Mollengraaf with SDSU Ag Communications
also provided excellent pictures of the aphids that were collected from Brookings on July 15.

I am finding soybean aphids with relative ease in Brookings and Minnehaha counties.

Soybean aphids are very small insects but could still be seen with the naked eye.
A magnifying lens would help in the identification process.

Soybean aphids are the only aphid species that multiply on soybean in South Dakota.

Most soybean aphids found on soybeans right now are the wingless form. They are
about one-sixteenth of an inch long and yellowish to yellowish-green in color. They
have syringe-like mouthparts and feed on the soybean sap. A magnifying lens will
also reveal that they have a pair of black “tail pipes” on the rear.

The presence of ants on soybean plants may be a sign that the soybean aphids are
also around. Ants tend aphids for their honeydew.

Soybean aphids have recently been seen in Brookings, White, and Aurora in Brookings
County; Montrose in McCook County; and Brandon, Crooks, Hartford, Humboldt, Wall
Lake, Wayne Township, and Wellington Township in Minnehaha County.

The presence of soybean aphids in these locations were detected by SDSU Agronomy
Educator Craig Rosenberg, Crop Consultant Larry Sax, and USDA-ARS Research
Entomologist Louis Hesler.

Updates:

Jim Ruhland and Bruce Blume (both with Pioneer-A DuPont Company) and soybean
grower Wayne Binger reported the presence of soybean aphids in Buffalo Township,
Spink County on August 26. A follow-up survey conducted by Agronomy Educator
Mark Rosenberg and myself on September 6 revealed that the soybean aphid is
already widely distributed in Spink County. Spink County and Brown County are the
top two soybean producing counties in South Dakota.

Nathan Kizer - Agronomist with Howard Farmers Coop - reported on August 14 the first
occurrence of the soybean aphid in Miner County. According to Nathan, the aphid levels
northeast of Howard were quite low at 2-7 aphids per plant

Kari Salvorson - Crop Consultant and owner of Angel Crop Consulting - reported on
August 12 that the soybean aphids have already reached Campbell County. Kari
found the aphids on soybeans near Mound City. As far as we know, this is the farthest
west that the soybean aphid has spread in South Dakota.

Keith Parker - Crop Consultant with Rolling Plains Consulting - reported the first soybean
aphid infestation in Day County on August 9. Keith found the infested soybean plants
close to a shelterbelt that may have buckthorns. Buckthorns are where soybean aphids
overwinter as eggs.

On August 8, Gary Erickson (Brown County Agronomy Educator) reported that soybean
aphids were also present in Marshall County.

John Carstens (Agronomy Manager, Akron IA Farmers Coop) reported the first
soybean aphid infestation in Union County on August 1. John, who is an alumnus
of SDSU, found the infested soybean fields near Spink, SD. A follow-up survey
conducted by Agronomy Educator John Gille and myself on Sept. 12 revealed that the
soybean aphid is already widespread in the county.

Gary Erickson, Dale Curtis, and myself surveyed Brown County on July 25 and
detected the soybean aphid there.

Randy Tornberg - Agronomist with Arlington Farmers Elevator reported the first
case of soybean aphids in Kingsbury County on July 19.

Vermillion Fertilizer and Meckling Fertilizer reported the presence of soybean aphids in
Clay and Yankton counties on July 19.

Chuck Langner (Codington County Agronomy Educator) reported the first soybean aphid
infestations in Codington, Clark, and Hamlin counties on July 18.

Also on July 18, Crop Consultant Bob Narem reported the first soybean aphid in
Roberts County close to Sisseton (Easter Township).

Crop Consultant Robby Dressen reported the first soybean aphid infestation in Turner
County near Centerville on July 16.

Agronomist Gary Nelson reported the first soybean aphid occurrence in Lincoln
County near Harrisburg on July 17.

University of Minnesota research in 2001 has indicated that spraying for the soybean
aphids will be beneficial if an average of 250 aphids per plant or more were found
throughout the field.

Growers are encouraged to look for aphids from at least ten locations on the field to
properly gauge the representative aphid infestation of the entire field. Soybean aphids
usually infest the borders first then spread into the whole field.

The mere presence of soybean aphids does not mean that the field needs to be sprayed.
I am of the opinion that most SD soybeans will not need treatment this year.

Insecticides labeled for the soybean aphid on soybean and their recommended rates and
pre-harvest intervals (PHI) are as follows: Asana XL (5.8-9.6 fluid ounces per acre, 21
day PHI); Furadan 4F (0.5 pint per acre, 21 day PHI); Lorsban 4E (1-2 pints per acre,
28 day PHI); Mustang (3.0-4.3 fluid ounces per acre, 21 day PHI); Penncap-M (1-3 pints
per acre, 20 day PHI); and Warrior (1.92-3.20 fluid ounces per acre, 45 day PHI).

Always read and follow label directions. Consult the label for restricted entry intervals (REI).

Soybean aphids were first detected in South Dakota in late September 2001 in
Brookings, Moody, and Minnehaha counties. The first record of soybean aphids in the
United States was made in Wisconsin during the summer of 2000.