Update on fusarium head blight and stripe rust of wheat
Wheat growth stages vary across Indiana, but many fields are flowering or beginning to flower in areas of southern/central Indiana. These regions are at low to moderate risk for Fusarium head blight (FHB) development, however the intermittent rains and warmer temperatures will likely increase risk of disease development.
Stripe rust of wheat has now been reported in several counties in southern IN. The disease is at low incidence and severity in fields. The fungus that causes stripe rust (Puccinia striformis) produces a yellowish or orange spore, and pustules appear in a row on infected leaves, giving it a “striped” appearance. Purdue Extension Bulletin BP-79-W, “Identifying Rust Diseases of Wheat and Barley” is available to aid in diagnosis of stripe rust, and can be found at the following link: <https://mdc.itap.purdue.edu/item.asp?itemID=19349>. Fungicide applications for FHB management in these areas will also limit development of stripe rust.
Fields should be scouted for stripe rust prior to the decision to make a fungicide application. Stripe rust has not been confirmed in central or northern IN yet, but may develop and coincide with the timing of a fungicide application for FHB suppression in these areas. Fungicide applications to manage FHB need to be made at Feekes 10.5.1, or early flowering. The fungicides available for Fusarium head blight control are also effective at managing stripe rust, should the need arise. Foliar fungicides available for control are listed in the foliar fungicide efficacy table developed by the North Central Regional Committee on Management of Small Grain Diseases or NCERA-184 committee, and through the Purdue Extension bulletin BP-162-W: <https://ag.purdue.edu/btny/Extension/Pages/ExtPubs.aspx>.
The foliar disease Septoria/Stagonospora leaf blotch has been observed in fields throughout the state, but is still at relatively low levels in most of Indiana. Symptoms of this disease are now visible on the leaves just below the flag leaf in areas in central Indiana. Fungicides applied at flowering for FHB suppression will also provide some level of protection from foliar disease on the flag leaf. Producers in northern IN who are considering a foliar fungicide application for Septoria/Stagonospora leaf blotch control through boot stage should keep in mind that applications made prior to flowering will NOT suppress FHB or the associated mycotoxin deoxynivalenol, or DON. If the risk for FHB increases after foliar fungicide applications are made, it may be necessary to make another application at flowering for FHB suppression.
Producers in central and northern Indiana should carefully monitor the Fusarium head blight risk map over the coming weeks as wheat is beginning to flower: <http://www.wheatscab.psu.edu/>. If temperature and humidity increase, the risk for disease development could increase in other northern and central counties in the state and fungicide applications to suppress disease may be necessary.