ROLE OF WARM-SEASON WEEDS IN SPOTTED WILT EPIDEMIOLOGY IN THE SOUTHEASTERN COASTAL-PLAIN

The role of endemic weeds in the epidemiology of spotted wilt must be determined in order to develop an integrated system to manage the dise ase. Field studies were conducted from 1990 through 1992 to determine concurrently the incidence of spotted wilt and population dynamics of thrips (Thysanoptera: Thripidae) on seven warm season weeds and three crop species planted in microplots. Weeds examined were Senna obtusifo lia (L.) H. Irwin & Barneby (syn. Cassia obtusifolia L.] (sicklepod), C. occidentalis L. [syn. S. occidentalis (L.) Link.] (coffee senna), J acquemontia tamnifolia (L.) Griseb. (smallflower morningglory), Ipomoe a lacunosa L. (pitted morningglory), Sida spinosa L. (prickly sida), D esmodium tortuosum (Sw.) DC. (Florida beggarweed), and Xanthium struma rium L. (common cocklebur). Crops evaluated were Arachis hypogaea L. ( peanut), Nicotiana tabacum L. (tobacco), and Capsicum annuum L. (bell pepper). All of the weed species were endemic to the southeastern Coas tal Plain and all crops were commercially produced in the vicinity of the test site. Most of the weeds were closely related to species ident ified as hosts of tomato spotted wilt tospovirus (TSWV). TSWV was rare ly detected in any of the weed species, while incidence in all crops i ncreased at a linear rate throughout the growing season. Order of spot ted wilt incidence in crops was peanut > tobacco > bell pepper. Thrips species diversity differed among weeds and crops. Thrips vectors were highly attracted to susceptible crops, especially peanut. While the w eed species we studied were susceptible to spotted wilt, they were not preferred hosts for the thrips vectors. Any occurrence of spotted wil t in weeds is probably due to random feeding by the vector. The warm-s eason weeds studied did not contribute significantly to the epidemiolo gy of spotted wilt.