In Western Wisconsin this week, LaCrosse, Buffalo, and Vernon counties are experiencing extremely high (800 – 1000+ aphids/plant) soybean aphid populations.

UW Extension, consultants and growers are treating fields in these areas where aphid densities have reached or are exceeding threshold of 250 aphids/plant over 80% of the field. Steve Huntzicker, UW-Extension La Crosse Agricultural Agent, observed soybean aphid densities have increased to exceed threshold in many fields between 20 July and 25 July. In addition, the soybean aphid suction trap located in Eau Claire, WI (western WI) registered high winged soybean aphid numbers (57) on 20 July, indicating significant field populations generating winged females.

Statewide, the WI Pest Survey (WI DATCP) completed a systematic survey to estimate peak soybean aphid population densities. Overall, soybean aphid densities are erratic statewide, with economic populations (exceeding the economic threshold of an average of 250 aphids/plant throughout 80% of the field) scattered throughout the southeast, south central and west central portions of the state.

Moderate populations, 100-250/plant, were detected in some Dane, Green, Racine, Rock and Walworth County fields in the south central and southeast regions. As soybean aphid populations continue to increase, many fields in these areas have potential to develop economic populations in the week or two ahead. Non-economic populations of fewer than 100 aphids/plant were detected in Columbia, parts of Dane, Dodge, Kenosha, Lafayette, and Racine and Washington counties in southern WI. Low populations were also noted in eastern WI (Brown, Calumet, Fond due Lac, Outagamie, Sheboygan and Winnebago). Survey Information Courtesy of WI DATCP, Wisconsin Pest Bulletin.

2007 Soybean Aphid Scouting and Management Recommendations

University of Wisconsin Extension Soybean Aphid Scouting and Management Recommendations were posted in the July 12th 2007 Wisconsin Crop Manager newsletter, Vol. 14, No. 19, July 12th, 2007.

Soybean fields should be evaluated without delay if soybean aphid populations are to be optimally controlled. Foliar sprays are most effective in reducing aphid numbers and minimizing resurgences when applied during the R2 (full bloom) to R4 (full pod) stages of soybean growth. Spraying at or beyond R6 (full seed) has not been shown to prevent yield loss. To assess soybean aphid densities, examine 20 to 30 plants over 80% of the field. Closely inspect all parts of the plants for aphids, particularly the stem, newest trifoliates, and undersides of the lower leaves. Treatment is warranted when the economic threshold of 250 aphids per plant on 80% of the plants is exceeded. – WI DATCP Wisconsin Pest Bulletin