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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) into a CTV-free sweet orange scion on sour orange rootstock block was monitored annually for 5 years, using severe isolate-specific and isolate-nonspecific monoclonal antibodies. The average percentage of trees infected with a severe isolate of CTV was 32, 32, 20, 25, and 28 for trees 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 ≤ 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 greater (P ≤ 0.05) with no aphid control than with stylet oil or MSR treatments.