IMPACT OF SUB-LETHAL DOSES OF NEONICOTINOIDS ON GLASSY-WINGED SHARPSHOOTER FEEDING AND TRANSMISSION OF PIERCE'S DISEASE

• Author(s): Walker, Andrew; Backus, Elaine; Purcell, Keiko;
• Abstract: The management of Pierces disease (PD) spread by Homalodisca coagulata, the glassy-winged sharpshooter (GWSS) is lacking a fundamental strategy and solid tactics. Among tactics under development is the use of insecticides to minimize numbers of GWSS and inhibit their feeding to reduce their ability to acquire the bacterium from infected vines and to inoculate uninfected vines. Two aspects of insecticides are necessary for this tactic to be successful: (1) they must affect GWSS immediately after they arrive on a vine; and (2) they must remain efficacious for a long time. Since 1998, we have examined the impact of insecticides on grapevines against the GWSS (Blua et al 2000, Redak and Blua 2001). We chose to study insecticides of the chemical class known as neonicotinoids because of their reputed inhibition of feeding by suckinginsects, and their long residual activity. Anti-feedant qualities are one of the important aspects of neonicotinoids. In a 1999 experiment conducted at the University of California, Riverside, GWSS caged on field-grown grapevines treated with Admire (imidacloprid, Bayer Inc) did not feed enough to generate visible amounts of excreta, which they normally produce in copious quantities. In contrast, GWSS on untreated vines generated a substantial volume of excreta. We concluded that Admire inhibits feeding by the GWSS. Our most recent experiments showed this effect for other neonicotinoids, including soil-applied Actara (thiamethoxam) (Syngenta, Inc) and foliar-applied Assail (acetamiprid) (Aventis, Inc) (Bethke et al 2001, Redak and Blua 2001). Most striking is our observation that neonicotinoids applied to grapevines in September of 1999 had a substantial impact on GWSS feeding almost a year later. This may, in fact, be more important to protecting plants from infectious sharpshooters then inducing mortality.
• Publication Date: Dec 2002
• Journal: 2002 Pierce's Disease Research Symposium