Early season fungicide use on wheat for foliar diseases
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
With the current prices for wheat, there is interest in looking at all options to increase yield. The use of including early season fungicide applications and their possible contributions to yield has been a hot topic for discussion lately. However, it’s important to remember that fungicides work mainly to protect the yield potential that is already present. Fields with the highest yield potential stand to gain the most from a timely application of fungicide to manage specific foliar diseases that are present. The information in this article summarizes the results of a number of University research trials around the country.
Early applications of fungicide applied at jointing (Feekes 5-6) are often made as a combined treatment with herbicides. The majority of university based research that looked at early season reduced rate applications for diseases like powdery mildew, leaf rust and leaf spots (Septoria, Stagonospora) found no significant yield advantage to an early season reduced rate of fungicide. Applications at jointing did not result in good disease control on the flag leaf during grain fill.
If high levels of leaf rust are present early in the season, or if stripe rust is present, an early application may be warranted. (Stripe rust is not an every year occurrence in Michigan.)
We had more of a normal winter with respect to temperatures and amounts of snowfall, compared with the previous two years. I have heard some concern about powdery mildew at recent meetings, especially on wheat that put on considerable growth going into winter. However, powdery mildew in fall doesn’t necessarily translate into disease pressure that reaches the flag leaf and impacts yield. Studies from multiple locations found that fungicide treatments for foliar disease were most effective when applied between flag leaf emergence and flowering. In most cases, effective disease control and yield protection can be achieved with one application to protect the flag leaf and /or the developing head. When foliar diseases are present above threshold levels, fungicide applications can improve yield. There are greater yield responses when disease pressure is high than when disease pressure is low.
The fact sheet, Management of Foliar Wheat Diseases available at http://fieldcrop.msu.edu/ provides guidelines for scouting and disease thresholds, along with efficacy ratings for fungicides for common foliar diseases. There is no substitute for going out and scouting your fields to evaluate disease levels before making a decision to apply fungicides.