Reflective Mulch and Acibenzolar-<I>S</I>-methyl Treatments Relative to Thrips (Thysanoptera: Thripidae) and Tomato Spotted Wilt Virus Incidence in Tomato

Abstract

Management of thrips-transmitted tomato spotted wilt (TSW) virus typically relies on tactics that either reduce the thrips vector numbers or change the plant's response to the virus to reduce economic loss. We attempted to quantify the interaction between two such tactics, reflective mulch and the plant activator acibenzolar-S-methyl (Actigard), respectively, on a TSW-susceptible tomato hybrid. A split plot experiment was conducted in 2009 and 2010 where main-plots were three types of plastic mulch (two metalized reflective vs. black) and subplots consisted of a range of plant defense activator applications. TSW pressure varied over year with 80% of untreated plants having TSW in 2009 where as <7% of plants was infected in 2010. No significant interaction between mulch and subplots was found relative to thrips and marketable yield in either year. In 2009, the seasonal average of Frankliniella fusca (Hinds) populations and incidence of TSW were significantly lower and yield significantly higher on both reflective mulches than on black mulch. Seasonal averages of thrips and fruit yield differed significantly among treatments of acibenzolar-S-methyl. However, there was a significant acibenzolar-S-methyl by mulch interaction relative to TSW incidence. In 2009, a minimum of acibenzolar-S-methyl at transplant plus foliar treatments at 10 and 20 d after transplant was required to significantly reduce TSW incidence compared with untreated plants before harvest. Under lower TSW pressure in 2010, average TSW incidence was significantly less in all plots treated with acibenzolar-S-methyl treated plots compared with the check. Acibenzolar-S-methyl treatments functioned better with the thrips reducing tactic, ultraviolet-reflective mulch. We propose that acibenzolar-S-methyl is less effective than metalized reflective mulch in reducing the incidence of TSW in tomato.