Wheat Head Scab Update

This is the time to begin thinking about head scab and its management with fungicide. Heads are most susceptible to the scab fungus during flowering and infection is favored by warm, wet or humid conditions. Fields in the Northern half of the state that are likely to reach flowering around May 31. Moreover, conditions have been humid; both rainfall and high humidity favor scab development and vomitoxin contamination of the grain.

Continue to use the prediction tool to assess the risk for scab over the next 7 to 10 days, and be prepared to apply Prosaro or Caramba, if moderate to high risk is predicted at the time the crop reaches the flowering growth stage. Remember, these fungicides are most effective against scab and vomitoxin when applied at flowering. However, if you are unable to treat your field at the flowering stage, you can still get good scab and vomotoxin control if you apply the fungicide up to six days after flowering. Later applications may be less effective, and most importantly, may be off label, since the pre-harvest interval for both Caramba and Prosaro is 30 days. On average, wheat in Ohio is usually harvested between 40 and 45 days after flowering.

The Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu/ is a predictive system to help growers assess the risk of Fusarium head blight in their region. Major outbreaks of Fusarium head blight are associated with specific weather patterns prior flowering of the wheat crop. The models estimate the risk of a Fusarium head blight epidemic with greater than 10% field severity using weather variables observed seven days prior to flowering. Weather during this pre-flowering time period influences the reproduction of the fungus that causes head scab. Testing of these pre-flowering models indicates that the models are correct about 75% of the time. The models are only one source of information available to help make management decisions. We strongly encourage you to consult with local extension specialists, and crop consultants to determine if fungicide applications are needed to suppress Fusarium head blight in your area.

 

Fusarium head blight is caused by the fungus Fusarium graminearum. The fungus attacks the grain directly and can result in serious yield losses. Losses may also be compounded by mycotoxins that are produced by the fungus in diseased grain. Symptoms of disease include tan or brown colored lesions that may include single spikelets or large sections of the wheat head. No single disease management option can completely eliminate the risk Fusarium head blight; therefore, the disease is best managed with an integrated approach. This integrated approach begins with selecting the best available genetic resistance but may also require the timely application of a fungicide to suppress the disease when weather favors disease development.

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