Asian soybean rust: Syngenta spore trap project

Early detection of Asian soybean rust (ASBR) (Phakopsora pachyrhizi) is essential for optimum control with fungicides. One method of early detection is the use of sentinel plots, soybean plots planted before the main crop. Another method used in Paraguay is spore trapping, where ASBR-like spores can be detected up to 10 days before disease appears. To test this method in the US, 96 spore traps were placed in 13 states from WI to GA in the summer of 2005. Spores were caught on glass slides coated with petroleum jelly and exposed in the field for one week. The slides were sent to the University of Arkansas. Spores were identified as ASBR-like spores based on size, shape, pigmentation, and surface ornamentation from pictures and killed urediniospores of P. pachyrhizi. ASBR-like spores were found in each of the 13 states and in 66 of the 96 spore traps. ASBR did not develop at most sites. However, at the 12 sites in GA and AL where the disease did develop, ASBR-like spores were found 5 to 77 days before disease was found at the site (average 30 days), except at one site in GA where disease developed 31 days before spores were found.