Soybean aphid densities in commercial fields and UW Entomology research plots are summarized here from a variety of sources. Overall, field densities are low and have not reached economic threshold levels. A few scattered fields have reached threshold, one USDA IPM PIPE soybean sentinel plot in Buffalo County exceeded threshold this week (see map with this article), but no major outbreaks to date http://www.sbrusa.net/ . 

 

In our UW Madison entomology field crop small plot research plots (soybean host plant resistance, aphid-virus interactions, and organic transition) located at Arlington and West Madison, WI we have not reached the economic threshold of 250 aphids per plant to date. For example, population densities are ranging between 2 and 65 aphids/plant on average at West Madison, with nearly 100% of our plots infested. Therefore, there is certainly a well distributed source population and if densities increase over the next week or two it should be plot wide. UW Entomology colleagues Scott Chapman, PhD and Bryan Jensen, IPM coordinator, and I have not applied insecticide to our soybean aphid efficacy trials to date either, as plots are below threshold.

 

From commercial fields statewide, here are reports I am receiving this past week. All reports are based on whole plant counts conducted on 20-30 plants per field throughout field. Bill Halfman, Agriculture Agent, UW Extension Monroe County, scouted five soybean fields July 9^th, all at R1 growth stage, with wooded field borders and on lighter textured soils. Soybean aphid populations in two fields were extremely low. Three of the fields were hovering at the 250 aphids/plant economic threshold. Bill is watching the fields to monitor for increase over the next week.

 

Krista Hamilton, WI DATCP Pest Survey, and the Pest Survey team scout approximately 60 soybean fields each week statewide. Krista reported this morning that although a few scattered fields in the statewide survey have been found at or above threshold, no major outbreaks so far and no field averages have exceeded 500/plant. On July 6^th, WI DATCP recorded their first threshold field of the season in Jefferson County at 280 aphids/plant on 100% of the plants. No other economic populations in 57 soybean fields surveyed the first week of July. For current updates, which will post Friday July 13^th please visit the WI DATCP Wisconsin Pest Bulletin http://pestbulletin.wi.gov/index.jsp

 

The USDA IPM PIPE website is up and running with weekly soybean aphid reports from multiple locations within WI and throughout the U.S. The Pest Information Platform for Extension and Education (PIPE) http://www.sbrusa.net/ began with sentinel plot monitoring throughout the U.S. for soybean rust. Since 2006, PIPE has expanded to include soybean aphid. 

 

Instructions are provided on the home page www.sbrusa.net for navigating the site, both Soybean Rust and Soybean Aphid interfaces. The soybean aphid map has its own color coded map where you can track aphid population densities regionally and nationally. Check the drop-down menu in the upper right corner of the PIPE homepage. Then using the zoom tool at the upper left of screen you can select Wisconsin to zoom in for an update of statewide aphid densities. You can also read a summary of soybean aphid reports and scouting and management advisories written by myself. UW extension plant pathologist, Craig Grau provides commentary for the soybean rust interface of the USDA IPM PIPE website.

 

UW Extension County Faculty from across Wisconsin report to the USDA IPM PIPE soybean aphid map each week. The map displays population densities for the sentinel plot field in each county. These are commercial fields and 20 plants are sampled from throughout the field. Below I have posted the most current WI map (updated July 12^th 2007). Similar to reports mentioned at the beginning of this article, the USDA IPM PIPE map for Wisconsin shows soybean aphid population densities ranging between 1-5; 6-39, or 0 per plant. Two sites on the map are higher at LaCrosse (40-149/plant rating) and Buffalo County (>500/plant), respectively.

 

Data presented on this map represents conditions observed in individual fields and does not represent conditions or a need for treatment in any other field.