Prelimary Report on the Apparent Control of Pierce's Disease (Xylella fastidiosa) with Admire (Imidacloprid) Insecticide

Abstract

Pierce's Disease is the major limiting factor in the production of European and American bunch grapes in the Coastal Plain and Lower Piedmont of the Southeastern United States. Pierce's Disease is also a significant problem in some areas of California. The disease has been impossible to control with insecticide sprays up to this point, because the leaf hopper vectors are xylem feeders and have minimal plant/insecticide contact. Admire was cleared for use on grapes 3 years ago, and an experiment was started near Tifton, Ga. Cultivars of European and American bunch grapes in this experiment include `Flame Seedless', `J. Riesling', `Cabernet Franc', `Reliance', `Mars' and `Canadice'. Experimental design is a randomize complete block with two replications and six vines per replication and treatment for a total of 72 vines in the experiment. Treatments are untreated control and vines treated with Admire (3.26 g/vine per application) in an aqueous solution of 1 to 2 L applied as a basal drench. Vines were planted in Mar. 1996 and applications of Admire have been applied in the early spring and mid summer of each year. Apparent Pierce's Disease symptoms became evident on some of the control vines in mid-summer 1997. By Fall 1997, some of the control vines were dead. This trend has continued in Spring 1998. Some vines treated with Admire show slight Pierce's Disease symptoms, but rate of disease development is much slower than in the control vines. Based on company research with virus transmission on other crops, even better results can be expected when large blocks are treated with Admire. Current results on this experiment will be presented. Larger scale experiments are underway as well as experiments to determine the effect of Admire on the development of phony peach disease and plum leaf scald disease.