Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/1997
Publication Date: N/A
Technical Abstract: Leaf scald (LS) incidence should include detection of symptomatically and latently infected [with Xanthomonas albilineans(Xa)] sugarcane stalks. To estimate these, two techniques were evaluated: serology and isolation. Of the 116 symptomatic stalks examined, 99% were positive when tested by ELISA and dot immunobinding assay, but of the asymptomatic stalks only 1.4% tested positive. Davis's XAM medium detected Xa in 100% of the symptomatic stalks and in 16% of the asymptomatic stalks which had previously assayed negative serologically. Serological assays were used to estimate the incidence of LS symptomatic stalks. Latently infected stalks were estimated by subtracting the number of serological positives from the number of isolation positives. Field sampling was made after pre-harvest burning as the mechanical harvesters advanced through the fields. In ten fields surveyed, the incidence of a serological detection ranged from 1.1 to 12.2% and was assumed to be symptomatic stalks. For the same fields, the incidence of Xa detected by isolation (less the number detected by serology) ranged from zero to 16.1% and these were assumed to be LS latently infected stalks. These techniques were used where visual surveys could not be conducted because of restricted movement by the large biomass of tangled stalks and where burning made visual diagnosis questionable.