Soybean aphids made their debut in early vegetative soybeans in Wisconsin over the last two weeks. Reports in this article are from V2 to V4 soybeans. Populations are not of economic concern at this time. Weekly soybean aphid scouting should begin by late vegetative soybean growth stage and before early reproductive stage (beginning bloom). It is a good idea to monitor soybean fields for arrival of soybean aphid and colonization in your fields while checking soybean stands.

 

2008 is expected to be a low soybean aphid year, as the North Central Region Soybean Aphid Suction Trap Network http://www.ncipmc.org/traps/ recorded very low 2007 Fall flights of soybean aphid returning to its overwintering host plant, buckthorn. Even though we expect a low aphid year, that is a relative term. In any year fields and regions of WI can experience economic threshold populations. Timing and variables during the season such as temperature and weather conditions can lead to rapid soybean aphid population growth. Soybean aphid scouting and monitoring for natural enemy presence among aphid colonies (predators, parasitoids, or aphid-killing fungus) is a key recommendation for 2008 as in past years.  

 

Please visit the UW Soybean Plant Health page for complete information on the economic threshold of 250 aphids per plant at R1-R5 soybean growth stages, and a refresher on scouting http://www.plantpath.wisc.edu/soyhealth/aglycine.htm

 

Additionally, there are two presentations available on the Plant Management Network on soybean aphid. These presentations were made by Dr. David Ragsdale, Professor of Entomology at University of Minnesota. The first presentation covers the biological aspects of soybean aphid (reproduction, feeding habits, and its effects on soybean yield). The second presentation “Soybean Aphid: Economic Threshold and Economic Injury Level” discusses the points at which soybean aphid population densities go from benign to costly. Here is the URL:

http://www.plantmanagementnetwork.org/edcenter/seminars/SoybeanAphid/ 

Krista Hamilton, WI Dept. of Agriculture Trade and Consumer Protection, State Survey Coordinator, reported her first soybean aphids from commercial fields June 19th. In southern WI: Columbia Co., 6 per 100 plants infested with 1-19 aphids, Dodge Co. she found only 1 per 100 plants were infested, the infested plant had 34 aphids (and a few ants, which alerted her to look closer).

 

June 23rd John Gaska and Branden Furseth (UW Soybean Extension and Research Program) found soybean aphids in a soybean seed treatment experiment at the Arlington research station as well as at their soybean research trials located at the West Madison research station. John Gaska reports that soybeans were at V3-V4 stage. A few plants per hundred sampled (low percent infestation to date) had 20-30 aphids per plant. See Dr. Shawn Conley’s (UW Madison Soybean Agronomist) report at The Soy Report www.thesoyreport.blogspot.com

 

For more information updated throughout the season, please visit the Soybean Aphid IPM PIPE http://soybeanaphid.ipmpipe.org or http://sba.ipmpipe.org