Issue No. 3, Article 6/April 10, 2009
Applying Foliar Fungicides to Early-Stage Wheat
Early applications (Feekes 5--just before jointing, when wheat begins growing rapidly) of reduced-rate fungicides are currently being discussed and promoted in some regions of the state. The possible benefit of applying a fungicide this early would be that it could potentially be applied with a herbicide. The potential downfall is that it may not be as effective as a single application later in the season for protection of the flag leaf (Feekes 9). Results from trials conducted at Southern Illinois University at Carbondale and Belleville from 2004 to 2007 (Dr. Bryan Young's research) and at the University of Illinois in 2008 (my research) indicate that full-rate fungicides applied at Feekes 9 or 10 have shown a more consistent benefit than half-rate fungicides applied at Feekes 5. Unless leaf, stem, or stripe rust is already apparent at Feekes 5, an application this early will potentially have less benefit than an application at Feekes 9.
A trial conducted at Carbondale (SIU research by Dr. Bryan Young) in 2004 and 2005 evaluated Headline applied at 3 fl oz per acre at Feekes 5 and Headline applied at 6 fl oz per acre at Feekes 9. The study was conducted over 18 to 25 wheat varieties per year. In 2004, the full-rate application at Feekes 9 was more effective at controlling foliar diseases than the half-rate application at Feekes 5, and yields were also higher after the full-rate Feekes 9 application than after the half-rate Feekes 5 application or when untreated. In 2005, only small differences were detected between untreated and Headline-treated plots, regardless of the rate and application timing. Foliar disease pressure was much greater in 2004 compared to 2005, which is likely why Headline fungicide increased yield on several varieties that year.
Effect of Headline fungicide applied at different rates and timings averaged over several varieties planted at Carbondale, Illinois, in 2004 and 2005. (Research conducted by Dr. Bryan Young, Southern Illinois University.)
--Carl A. Bradley
Carl A. Bradley