Stripe rust has been confirmed on wheat in eastern Lincoln Co., Arkansas. Other reports have indicated wheat affected in fields in Lee Co.
Much like 2012 and 2013, the disease is appearing early in the season and will have to be managed sooner rather than later. In affected fields, yellow orange pustules of the fungus can be found on yellow leaves in aggregated patches. The spores are spread by wind to neighboring plants and when there is free water on the leaf surface, germinate and infect, which results in profuse sporulation and disease spread.
Most of the varieties grown in the state have adult plant resistance to the disease. This means that young plants are susceptible and become more resistant to stripe rust as the season progresses and the plants mature.
Of concern is the susceptibility of the plants early season, which can cause a measurable yield loss if the disease progress is extensive and not treated. Further, the resistance is race specific and is functional until a new race is selected out of the present population. As the disease progresses, more disease offers a greater opportunity for population increase for virulent races so early control is beneficial in this respect as well.
Many fungicides labeled for use in wheat have demonstrated good control of the fungus and once applied will prevent new infections even though some sporulation on diseased plants will continue. A convenient timing for fungicide application may be in a tank mix with herbicide, but application based on disease progress and assessment of weather conditions is always preferred.
Variety performance against stripe rust can be found online here and the updated list of fungicides labeled for control of stripe rust can be found here along with a product efficacy table.
