CEREAL RUST EPIDEMIOLOGY STUDIES USING ROADSIDE TRAP PLOTS IN THE SOUTHEASTERN UNITED-STATES

Cereal rust trap plots were planted along a 2,687-km route using inter state and federal highways in the southeastern United States. The tech nique was developed and evaluated to study the oversummering and overw intering biology of four major cereal rusts: leaf and stem rusts of wh eat, and crown and stem rusts of oats. The interstate highway system w as selected to provide ease and speed of access for planting and monit oring, and for general safety reasons. Markers placed at 20-ml (32-km) intervals were selected for the trap plot sites to conform to establi shed cereal rust survey techniques. Susceptible, well-adapted cultivar s were preplanted in the green-house for subsequent transplanting at t he sites and/or seeded directly to increase the likelihood of plot sur vival. The trials were conducted over a 7-yr period, 1986-1993, with 3 yr used to study oversummering (planted in July and sampled in Novemb er) and 4 yr to study overwintering biology during the normal growing season (planted in November and sampled in April). Severe droughts lim ited survival in 1986 and 1987. In 1988, several plots along the Gulf Coast were flooded and died. Planting and culturing techniques were mo dified each year to improve survival. Oversummering data indicated thi s method is useful for monitoring cereal rust survival during the summ er, but plot survival rates under extreme stress may limit the effecti veness of the technique. Trials during 1990-1993 were promising, suppl ying both incidence and virulence data to supplement USDA-ARS Cereal R ust Laboratory annual surveys. The technique is not only effective for cereal rust research, but is also suitable for detecting other windbo rne pathogens, cereal and peanut viruses, and insect pests at a reason able cost.