If we had a map of crop diseases in the U.S., the Western Great Plains would be flashing red and yellow lights right now. Crop reports are coming in from Extension educators from Louisiana to North Dakota advising farmers to scout their wheat fields and be prepared to take appropriate action.
Stripe rust, which had previously been kept in check by resistant and tolerant varieties of wheat, developed a new race and greatly expanded its distribution in 2015. Our recent ‘relatively’ warm winter and pockets of snow coverage allowed rust spores to overwinter, resulting in new infection sources scattered in areas throughout most wheat producing states. For those of you who have seen our weekly weather video, you know that the cool and wet weather pattern that has set up between the Rocky Mountains and the Mississippi River will bring about conditions that are likely to aggravate stripe rust. And just in case you forgot, stripe rust, if unchecked, can be nasty, reducing yields by up to 50%.
Unfortunately, wheat is maturing quickly now and timing a fungicide spray between expected rain events can be challenging. Since fungicide labels have strict timing windows for effectiveness and for Pre Harvest Intervals (PHIs), it is possible that some wheat may not get the necessary treatments to forestall stripe rust. And just to make things more interesting, other diseases such as scab (Fusarium head blight) and leaf rust can also be more prevalent due to strong winds and splashing rain moving spores about. Growers who have concern about the susceptibility of their wheat varieties to any of these diseases will be examining their stands closely.