By Erin Hodgson
The "2016 Yellow Book for Soybean Aphid" (CROP 3109) is now available as a free download through the Extension Store. The publication provides soybean aphid treatment recommendations and application rates based on research conducted at the Iowa State University Northeast Research and Demonstration Farm and the Northwest Research and Demonstration Farm in 2016. The report also includes insecticide effectiveness on the soybean aphid and yield, and information on the soybean aphid life cycle and scouting methods.
The Yellow Book has been published annually since 2005 with trial results and evaluations. Erin Hodgson, associate professor and extension specialist in entomology at Iowa State University, has been writing the publication since 2009.
For the first time during the 2016 growing season, insecticide failure was confirmed in Iowa. Pyrethroids are a common insecticide group, but did not have any knockdown in this commercial field.
“This may force farmers to switch to a different kind of insecticide, most likely organophosphates,” Hodgson said. “If pyrethroid resistance becomes more common, it limits the tools that can be used and can increase input costs.”
Checking to make sure insecticides are working now becomes a priority.
“If you are going to apply a foliar insecticide, make sure to go back and scout to insure there are no survivors after application,” Hodgson said.
Hodgson will present much more information about the insecticide failure during the 2017 Iowa State University Extension and Outreach Crop Advantage Series meetings.
Researchers used land in two sections of the state, getting dramatically different results in each area. Soybean aphid populations never reached their threshold at the Northeast Research Farm, while significantly exceeding that threshold at the Northwest Research Farm.
“Overall in my evaluations, treating with insecticides at the economic threshold provides a strong yield response,” Hodgson said. “That tells me the threshold is still valid and farmers should adopt scouting to reduce input costs.”