NATURAL FIELD SPREAD OF MILD AND SEVERE ISOLATES OF CITRUS-TRISTEZA-VIRUS IN FLORIDA

The effectiveness of five different aphid control regimes in delaying movement of mild and severe isolates of citrus tristeza virus (CTV) in to a CTV-free sweet orange scion on sour orange rootstock block was mo nitored annually for 5 years, using severe isolate-specific and isolat e-nonspecific monoclonal antibodies. The average percentage of trees i nfected with a severe isolate of CTV was 32, 32, 20, 25, and 28 for tr ees treated with Temik, Temik + Meta-Systox R (MSR), MSR, stylet oil, or no aphid control, respectively, at the conclusion of the experiment (5 years). These percentages were not significantly different (P less than or equal to 0.05). The average percentage of trees infected only with mild isolates was 13, 10, 7, 7, and 17 for the above treatments, respectively. The infection with mild isolates was significantly grea ter (P less than or equal to 0.05) with no aphid control than with sty let oil or MSR treatments.