Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
We had quite a few rain events during the flowering windows for barley and wheat, which kept us at high risk for Fusarium Head Blight (FHB). Once wheat has flowered, symptoms of FHB are visible in 18-24 days. Heads with FHB will have bleached florets or bleached sections of the head (Figure 1) and may have pink growth on spikelets. (Glume blotch typically has more of a grey appearance). You can follow these steps to assess the level of FHB present in your field.
Figure 1: Wheat heads with symptoms of Fusarium Head Blight
- For every 10 acres of field, randomly select one spot to survey.
- Keeping your line of sight above the wheat heads, walk 40-50 yards and randomly pick 10-20 heads to place into a bag. (You don’t want to be looking down and biasing the heads you select).
- Once you have randomly collected the heads, rate them for the percent of FHB on each head by looking at the visual symptoms (bleaching or pink growth on spikelets).
- After you have recorded values for each head, determine the average percent FHB severity by dividing the sum of disease severities by the total number of heads collected.
(Ex. You rate 10 heads with severity values: 0, 10, 30, 0, 0, 20, 10, 0, 0, 0. These add up to 70. 70/10 heads = 7% FHB severity)
Higher levels of FHB are typically associated with elevated levels of DON and possible issues with yield and test weight.
- Repeat this assessment as needed to get an overall rating for the field. Fields with greater than 10% FHB severity are at higher risk for yield losses or elevated DON. Fields with elevated DON should be harvest as early as possible and you may want to consider increasing combine fan speeds and shutter openings to reduce the amount of scabby kernels harvested.