Nathan Kleczewski Ph.D
Extension Specialist- Plant Pathology
Department of Plant and Soil Sciences
I have spent a great deal of time going over the literature on Fusarium head blight (FHB) management in wheat. Fusarium head blight also impacts barley, a crop that is important in the region for malting and feed. FHB management is similar but a little different in barley, and a good deal of this is a result of the growth and development of barley in relation to wheat.
In wheat we have heads that emerge from the boot. After emergence anthers will pop, and flowering will occur. Wheat is most susceptible to yield loss and DON when young anthers are exposed. Therefore, we recommend starting fungicide timings at Feekes 10.5.1, or when about 35% of the main tillers have just started flowering.
In barley things are different. Pollinization occurs in the boot or as the heads emerge from the boot. As a result, yield losses from FHB are not typically an issue in barley as the plant has a natural barrier from the FHB pathogen. However, if weather becomes wet and rainy after head emergence, spores of the FHB pathogen can land on heads, colonize the glumes, and produce DON. Thus, you may not see the bleached out heads as you do in wheat, but you may see some reddish discoloration in the glumes. Your DON levels may be elevated as well.
If you are selling barley for malting this is a major issue as the tolerance for DON is very low. Tolerance levels are a bit higher if you are selling it for feed. Most individuals in Delaware and Maryland fall into the feed category, although there has been interest in local sources of barley for our regional and local microbreweries.
Often barley escapes disease because it flowers early and matures before we see moderate/warm temperatures. Also the value of the crop might not justify a more expensive fungicide application. However, when temperatures are above 60 degrees F and it is wet, like it was last year, FHB outbreaks occur. The FHB pathogen simply requires a little more time and rain for inoculum to build and be released.
Some people in Delaware and Maryland plan on applying Prosaro, Caramba, or Proline to their barley to protect it from potential DON contamination. In barley, you want to shoot for over 35% of main tillers with heads fully emerged, and apply your fungicide within 5-6 days of this point. If you have to choose between spraying 3 days early and 3 days late, I suggest spraying late. Fungicide applications to the boot will not move to the head, and when those heads emerge they will be unprotected from potential future infection events.
Source : udel.edu