Even though we did not have high levels of scab and vomitoxin this year, we still need to keep this disease in our minds as we select varieties to plant this fall. In the past, there were very few Ohio-grown winter wheat varieties with decent scab resistance, and some of those varieties yielded poorly or did not grew well under our conditions.
Today we have far more varieties with very good scab resistance in combination with very good yield potential. So, as you prepare to plant wheat this fall, scab resistance should be a top priority on your list when selecting a variety.
However, remember, no variety is completely resistant or immune to scab, so if conditions are wet and humid during flowering, even varieties considered resistant will develop scab and become contaminated with vomitoxin, but, disease and toxin levels will likely be lower in resistant varieties than in susceptible varieties.
When conditions are favorable for scab, producers who plant resistant wheat varieties and applied a fungicide at flowering usually see lower levels of scab and vomitoxin than those who plant susceptible varieties. With a scab resistant variety, growers tend to see greater benefit from the use of fungicides if scab develops.
In general, compared to the most susceptible varieties, scab and vomitoxin reductions may be as high as 70% when fungicides (Prosaro or Caramba) are applied to resistant varieties, and only about 50% when susceptible varieties are treated.
This table (click here) shows the most scab resistance varieties in this year’s wheat performance trials. There were several varieties rated as either R or MR. R = resistance, indicating that a variety has resistance comparable to Truman, one of the most scab resistant soft red winter wheat varieties.
MR = moderately resistant, indicating that a variety has resistance comparable to Freedom, the old resistant standard. Other rating include MS = moderately susceptible, and S = susceptible.
More information about the varieties shown in the table will be published in the 2017 Wheat Performance Trial here.
NOTE: R does not mean that the variety will not become infected; it means that it is among the most resistant we have at this time, based on multiple years of testing. You will still need to treat a variety rated R or MR with a fungicide to control scab if it becomes wet and humid next spring.