ANTAGONISTIC EFFECTS OF COPPER AND VENDEX FOR CONTROL OF CITRUS RUST MITE, 2000

Copper has been reported to shorten residual control of citrus rust mite with Vendex (Dean 1979, J. Rio Grande Valley Hortic. Soc. 33: 55-57; Childers 1994, Fla. Entomol. 77: 349-365), and although Lye et al. (1990, Fla. Entomol. 73: 230-237) saw no such effect, tank mixing this product with copper is not recommended in Florida (Childers et al. 2000, Florida Extension Service, University of Florida, Gainesville). Our objective was to evaluate the combined effects of Vendex and copper compared with copper alone under conditions in a commercial grapefruit orchard in southwest Florida. The trial was conducted at the Duda Grove in Hendry County, FL, on 35-yr-old ‘Marsh’ grapefruit trees planted at 16 x 24-ft spacing. Four treatments including an untreated check were assigned in an RCB design with 10 tree plots, separated by a 10 tree buffer. There were four replications, each in single row separated by 2 buffer rows. A precount made 5 Jul on eight trees per replication produced an average of 1.6 CRM per standard 10x lens field. Test materials were tank mixed, copper added first, and were applied on 6 Jul using a Durand Wayland 3P100-32 air blast speed sprayer with an array of seven #3 T-Jet stainless steel cone nozzles per side, at a pressure of 400 psi delivering 100 gpa. Treatments were evaluated for CRM incidence seven times over a 76-day period starting 13 Jul. Four fruit, two per side, were sampled from 8 trees for a total of 32 fruit per plot. All mobile CRM were counted in two, 1.5-cm-diameter fields using a 10x Bausch and Lomb Triplex lens on each partially shaded side of each fruit.