FROM THE FOCUS ARTICLE: "Deadly Alternaria encountered again. Back in the August 13 and 20, 1999 issues of Focus, we reported a plant health problem of unknown origin (see previous newsletters with photographs). Isolation work conducted by Dr. Terry Wheeler, Experiment Station plant pathologist, later indicated that the disease was caused by an Alternaria species (fungus). Since the first sighting of this disease was in fields near Welch, it was jokingly dubbed the "Welch Mocus." We received some calls concerning a few fields with small areas with this symptomology in 2000. The disease has recently appeared again in a field south of Seminole. Fields infected in 1999 and 2000 were in western Dawson and eastern Gaines Counties. Crop genetics does not appear to be critical, as the varieties infected since 1999 have included Paymaster 1220 RR, Paymaster 1330 BG, Phytogen 569, Deltapine 5415 RR, Fiber Max 989, and Paymaster 2326RR.
The good news is that large affected acreage has not yet been reported or observed, but there is some concern. Rounded areas are typically about 10-30 yards in diameter. The plants are affected from the terminal down, with leaf wilting and desiccation evident. On recently infected plants, major veins on the underside of the uppermost leaves turn a brownish/maroon color. As the problem progresses, leaves eventually dry up and defoliate. The terminal in severely affected plants dies and curls downward. Symptoms then move down the mainstem. A maroon discoloration of the mainstem generally occurs, in conjunction with purplish lesions. Plants that have been affected for a longer period of time are generally several inches shorter than uninfected neighbors. Total fruit shed does not readily occur, as larger bolls are generally retained on dead plants. No vascular discoloration in the mainstem is apparent as with Fusarium and Verticillium wilts. We have provided pictures of the infected Gaines County field and symptomology. If anyone observes this disease, please call the Lubbock Center so we can record the location and affected variety."
