Soybean rust was found yesterday, August 7, for the first time in Arkansas this year. U of A Program Technician Amanda Greer made the discovery in a commercial soybean field at growth stage R5 near Halley in Desha Co in Southeast Arkansas. This is the same county in which SBR was first detected in 2012. Pustules were sporulating on 34 out of 35 leaflets collected with 3 to 22 pustules per leaflet. (See Fig. 1 for reference) Weather conditions are favorable for disease development, thus it is likely it will be found in other counties. Contact your county agent with questions concerning this disease before any action is taken.
Agents in the Southeast corner of the state should collect samples from the lower canopy from late maturing beans and sending them to the Plant Health Clinic in Fayetteville. Refrain from sending samples on Friday because they will degrade in hot post offices. Also, stack leaflets rather than cram into the plastic bag with moist paper towel when shipping.
Aerial blight is also showing up on beans. Clay and Lawrence Co. have reported finding the disease. Aerial blight warrants attention so agents, consultants and producers should look in fields with a history of aerial blight or sheath blight. The most noticeable symptom is the presence of hyphae (white web-like material) at base of plants or on leaves when beans cover the middles. Fungicide application may be considered. See MP 154 for fungicides, but azoxystrobin has been a good fungicide on aerial blight.
Please feel free to contact Travis Faske (firstname.lastname@example.org or 501-676-3124) with any questions regarding the development and management of these diseases.