Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
Fusarium head blight (FHB) epidemics are episodic, but when they do occur they can cause significant reductions in quality and yield. FHB will continue to be an issue for small grains due to corn production and the widespread use of conservation tillage. Thus, this disease, which historically caused few, localized outbreaks every 15-20 years now is seen more frequently across much larger areas. FHB should be on your radar if you are planting small grains. Current research indicates that suppression of FHB is achieved by using 1) a moderately resistant variety; 2) a recommended triazole fungicide applied at Feekes 10.5.1 or 4-5 days after Feekes 10.5.1; and 3) planting wheat following soybean. None of these practices used alone will provide sufficient suppression of FHB in a disease favorable year and must be integrated to maximize their suppressive effects.
Obviously rotation choices and variety selection are things that occur prior to the planting. However, the use of a fungicide is a within-season decision. One tool available to growers is the Fusarium head scab prediction website: http://www.wheatscab.psu.edu/. The website accurately predicts FHB outbreaks of >10% field severity roughly 80% of the time. Based on a current survey, the use of the website and its alert system has saved producers of small grains over $170 million.
How can you use this site? First, sign up for updates. Extension plant pathologists provide updates throughout the growing season. In Delaware I will be providing weekly updates until the crop starts to approach flowering, and every 3-4 days thereafter. Second, understand how to use the website. It is best to check the forecast around noon as this will allow the most current environmental data to be included into the forecast. The map will generate colors that indicate the level of risk for flowering wheat. Green = low risk; yellow = moderate risk; red = high risk (Figure 1). Thus, if your region is red, indicating high risk for FHB, but your crop is at boot, a fungicide application directed for suppression of FHB is not recommended. One weakness of the model is that it does not do a great job at predicting severe outbreaks during cool, wet conditions. Remember, anything above 60°F is sufficient for FHB as long as it is wet enough as wheat approaches flowering and there is a source of inoculum in the region (i.e. fields with small grains or corn residue). To account for this I suggest keeping a close eye on the commentary and local forecasts. Remember, the website is a tool to help you make informed management decisions but it is not an answer. Use all available resources when deciding to make fungicide applications to your wheat.
Another site I suggest you visit is ScabSmart: http://www.scabsmart.org/graincr.html. This is a great site with excellent information on FHB management. Lastly, sign up for updates from my Field Crops Disease Management Blog for alerts on diseases including FHB throughout the growing season: http://extension.udel.edu/fieldcropdisease/. I also post articles on important and new research, resources, and recommendations. This week’s blog entry is Fungicide use in Small Grains
Figure 1. An example of the FHB prediction website map during the FHB epidemic of 2013. Flowering wheat in yellow and red were at risk for FHB infection at this point in time.
There is no way to know if 2014 will be another FHB favorable year. The aforementioned resources will help keep you informed of potential outbreaks in the future.