Suppressive effect of acibenzolarSmethyl ASM on Tomato spotted wilt virus TSWV. Left, leaf from a control tobacco plant that was mechanically inoculated with TSWV. Right, leaf from a tobacco plant that was treated with ASM prior to mechanical inoculation with TSWV. The suppressive effect of ASM is evident from the absence of symptoms on the treated leaf. Spotted wilt disease, caused by Tomato spotted wilt virus TSWV, is a major yield limiting factor for peanut, tobacco, tomato and pepper crops in the southeastern US. Considerable progress has been made in developing management programs to reduce its impact on these crops. Cultivars with field resistance are available in peanut, tomato and pepper, but TSWVresistant tobacco cultivars are not yet available. Until recently, there have been few options available for practical management of TSWV in tobacco. Our research showed that the application of ASM andor imidacloprid resulted in significant reduction in disease incidence under field conditions Pappu et al., 2000. Crop Protection 19:349354; Csinos et al. 2001. Plant Disease 85:292296. ASM has been shown to elicit defense responses in treated plants resulting in systemic acquired resistance SAR. Preliminary results indicated that this SAR is possibly due to elevated levels of pathogenesisrelated PR proteins in ASMtreated tobacco plants. The nature of the induction of these PRproteins and the efficacy of ASM in suppressing TSWV in tobacco are being investigated. The leaf on the right was from a plant that was sprayed with 4 g active ingredient ASM per 7000 plants followed by washing with water. Mechanical inoculation was done 5 days after treatment, and the photograph was taken six days postinoculation.

Address: Coastal Plain Experiment Station, Tifton, GA 31793
Website: http://www.apsnet.org/online/Archive/2003/IW000022.asp