Any daylily or tulip enthusiasts may be bemoaning the recent cold snap that left many early-greening plants very sad across much of Iowa. Well, cold weather can be our friend as well. On April 7 and 8, a cold front pushed as far south as the Florida Panhandle, and kudzu growth was slowed or knocked back from this record-breaking frost. The freezing temperatures on the rapidly growing kudzu in this area could reduce the buildup and potential spread of soybean rust for several weeks. This frost came much later than their March 15 "frost-free" date.
To date, soybean rust has been detected on kudzu in nine counties in Florida and in five counties in each of Georgia and Alabama. However, much of the infected kudzu has been destroyed, and rust in some of those locations is no longer found.
Update on Fungicides
The EPA established a Section 3 registration for one of the most effective fungicides for management of soybean rust, Domark® (tetraconazole). Although the emergency exemption for Iowa will not expire until November 10, 2007, the new registration, along with the new labeling, can be used by growers in lieu of the currently approved Section 18 labeling. End users who have unused stocks under the Section 18 label are encouraged to follow the use directions and terms carried on the newly stamped Section 3 label.
Other soybean diseases that are on the Section 3 label include Cercospora leaf blight, frogeye leaf spot, white mold, powdery mildew, brown spot, and anthracnose.
Distribution of soybean rust in the southern United States after late frost in Florida.
This article originally appeared on page 114 of the IC-498 (6) -- April 16, 2007 issue.