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Printer Friendly Version P. A. Stansly, J. Conner, and D. Peach GRAPEFRUIT: Citrus paradisi (Macfady.) ‘Marsh' Copper has been reported to shorten residual control of citrus rust mite with Vendex (Dean, 1976), Childers, 1994, and although McCoy et al (1990) saw no such effect, tank mixing this product with copper is not recommended in Florida (Childers et al., 2000). Our objective was to evaluate the combined effects of Vendex and copper compared to copper alone under conditions in commercial grapefruit orchard in southwest Florida. The trial was conducted at the Duda Grove in Hendry county, Florida, on 35-year old ‘Marsh’ grapefruit trees planted at 16 X 24 ft. spacing. Four treatments including an untreated check were assigned in an RCB design 10 tree plots, separated by a 10 tree buffer. There were 4 replications, each in single row separated by 2 buffer rows. A pre-count made 5 Jul on 8 trees per replication produced an average of 1.6 CRM per standard 10x lens field. Treatments 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 7 times over a 76 day period starting 13 Jul. Four fruit, 2 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 Bauch and Lomb® Triplex lens on each partially shaded side of each fruit. CRM populations were lower on fruit treated with all products compared to the control through 46 days after treatment. At 60 days, CRM counts hand increased on all treated fruit but were lower on fruit treated with Vendex alone compared to Vendex plus either copper formulation, although none were significantly less than the control. At 76 days there were no significant difference among any treatments. Thus, there was no measurable antagonism between Vendex and copper through 46 days, although there may have been at 60 days. Further testing would be required to determine whether this is a chance or consistent effect. Childers, 1994. Effect of different copper formulations tank-mixed with fenbutatin-oxide for control of citrus rust mites (Acari: Eriophyidae) on Florida citrus. Flo. Entomol. 77:349-365. Childers, C. C., L. L. Knapp, C. W. McCoy, and P. A. Stansly. 2000. Citrus rust mite. In: Knapp, J. L. [Ed.], Florida Citrus Spray Guide. Florida Cooperative Extension Service, University of Florida/IFAS. Gainesville. Dean, H. A. 1979. Citrus rust mite control affected by certain pesticides. J. Rio Grande Valley Hort. Soc. 33:55-57. Lye, Ben-Huai, C. W. McCoy and J. Fojtik. 1990. Effect of copper on the residual efficacy of acaricides and population dynamics of citrus rust mite (Acari: Eriophyidae), Florida Entomologist 73:230-237. Florida Agricultural Experiment Station Journal Series No. N-02002.
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