ISU Corn and Soybean Initiative partner agronomists were surveyed in December about pest management issues in corn and soybean in the 2006 growing season. Here are summarized results of the survey concerning soybean pests. There were 17 usable responses from 28 companies polled, and responses geographically covered most parts of the state except extreme south-central Iowa.
Generally speaking, Iowa farmers faced comparatively low soybean aphid populations in the 2006 growing season. Approximately half of the agronomists reported no significant insecticide treatments made for soybean aphid control, with most of the acreage treated according to the 250 aphids per plant threshold occurring in northwest and north-central Iowa and also in far eastern Iowa. However, even in those areas, treated acres ranged from just 5 percent of acres to one report at the high of 30 percent. This is consistent with perceptions of the 2006 growing season being one with generally light soybean aphid infestations. Although it was not specifically asked, two agronomists in central and north-central Iowa volunteered that insecticide treatments for control of midseason bean leaf beetles were more of an issue in their areas than aphids in 2006. In addition, an agronomist in southwest Iowa mentioned concerns with cowpea aphid on alfalfa as being notable again in 2006.
For those areas where insecticides were applied for treatment of soybean aphid, products used were Warrior® at 2.5 ounces per acre, Asana® at 6-8 ounces per acre, Lorsban® 4E at 1 pint per acre, and one mention of Baythroid® at 2 ounces. For those areas where aphid populations were noted, untreated acreage was estimated to suffer from 6-12 percent (about 3-7 bushels per acre).
Foliar fungicides for disease suppression (corn and soybean)
The survey queried respondents about the use of foliar fungicides. In general, most reported scattered application of fungicides to both corn and soybean within their service areas, with about three to five times the acreage of soybean being treated compared with corn. The proportion of acreage treated with fungicide was small, approximately under 5 percent of total acres. However, that commercial crops and not just seed fields were treated is worth noting. The products reported being used include Headline®, Quadris®, Stratego®, and Quilt®.
Rich Pope is an extension program specialist in entomology with responsibilities in integrated pest management and pesticide applicator training.
This article originally appeared on page 69 of the IC-498 (3) -- March 26, 2007 issue.