Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
Small Grains Disease Update
Diseases remain hard to find in the majority of fields. When they do occur they are in the lower canopy. I have not seen any difference between fields or research plots sprayed with fungicides at flag or earlier and those without. It is likely that the penetrating cold temperatures dinged the primary source of inoculum, pushing the disease progress curve back. In addition, the cool, windy spring kept plants short and canopies dry. Temperatures are now warmer and fields can hold more humidity and that’s likely why we are now seeing things increase. In variety trials those varieties with the most powdery mildew are just barely present on the F-2 leaves. Read below for information on recent humid and wet weather as it pertains to flowering small grains.
Reminder to Sign Up for Head Blight Updates
Please remember to sign up for scab alerts and check the Delaware/Maryland Scab commentary on the FHB prediction Center website often. Now is the time to be making decisions pertaining to scab sprays as fields are getting ready to flower or are flowering in some cases. Remember the disease triangle- we need the pathogen on the host at a susceptible stage, AND the right environment. The extremely humid weather we had on Wednesday and Thursday was favorable for spore release and infection of flowering wheat. This resulted in an increase in the scab risk on 5/15. Heavy rains are expected Thursday evening through Friday, which will likely further increase scab risk in many areas of Delaware and Maryland. Luckily most people were not caught by surprise this year and already had lined up fungicide applications. The following is my commentary from the FHB prediction center website from 5/14/13: http://www.wheatscab.psu.edu/
“Delaware and parts of Maryland are now in a moderate to high risk level for scab. I expect this risk to continue through the weekend with heavy rains expected tonight and Friday. Fields entering flowering are at the highest risk for scab. The best fungicides for scab are Prosaro, Caramba, and Proline. Do not apply products containing a strobilurin (e.g. Aproach Prima, Quilt, Stratego, Headline, Quadris, etc) as strobilurins have been associated with elevated DON levels when applied to the head and scab occurs. There is a 5-6 day window after the majority of a field is flowering and conducive weather occurs to make a fungicide application and maximize efficacy. Ground rigs should have nozzles angled at least 15 degrees in the forward direction and apply at least 10 gallons per acre, with 15-20 being optimal. Aerial applicators should apply at 5 gallons per acre. Shoot for 300 to 350 micron droplet size. Prosaro, Caramba, and Proline will control foliar diseases.”
Any important updates will also be posted on the Field Crops Disease Management Blog: http://extension.udel.edu/fieldcropdisease/
The FHB risk map as of 5/15/2015 at 10:45 am.