The survey of Corn and Soybean Initiative retail partners (input suppliers), discussed in the special soybean aphid issue of the ICM Newsletter (January 23, 2006), asked additional questions about management for soybean rust in the 2005 growing season. Twenty of 26 partners who were polled responded. Statewide treatments with foliar fungicides varied from area to area, with more acres sprayed in the western half of Iowa. Among these 20 responses, an estimated 32,000 acres were treated. Areas treated ranged from 1 up to 10 percent of soybean acreage within their service communities, with most reporting 0 to 1 percent. Two respondents specifically stated that most applications were made not from direct fear of Asian soybean rust infection but rather with the phrase "treated for 'plant health' purposes."
The primary product used was Headline®, generally applied at 6 oz. per acre. Other products reported to be used were Quadris® and Stratego®. Some Section 18 product treatments made were likely off-label. Every partner but one said that treatments were all ground applied, the exception being very limited aerial spraying in southwest Iowa coupled with the usual ground applications. There may have been other occasional aerial applications, but they were the exception in Iowa.
We also asked about applying fungicides with either insecticides and/or herbicides. The most common mix was with Roundup® herbicide, but some mixing occurred with all of the midsummer pesticide treatments.
Concerning storage of "stockpiled" or leftover fungicides, most partners reported that they knew of little carryover product on-farm, but one respondent stated: "Yes, and there was more than we know about or want to think about across Iowa. [We discouraged stockpiling, but] brokers really loaded some up."
In summary, although there were some Asian soybean rust treatments made in 2005, the practice was infrequent. As we approach the 2006 growing season, our knowledge base about this disease should grow from local and national experiences.
This article originally appeared on page 49 of the IC-496 (3) -- February 27, 2006 issue.