Field Trials with Abamectin for Control of Citrus Thrips, 1995

Different rates of abamectin were compared against a standard (Veratran D) at five sites in the San Joaquin Valley during spring 1995 for control of citrus thrips. Treatments were applied to navel oranges with each treatment replicated twice at each site. Each replicate plot was at least 6 rows wide (most were larger, 2 acres or more). Citrus thrips infestation due to first and second instar immatures was monitored after petal fall by examining 10 fruit selected randomly from 10 trees of uniform vigor in each plot (200 fruit/treatment) except that 25 fruit were monitored in one of the two plots for each treatment at S & J 6-9 by Andrea Gjerde. Citrus thrips fruit scarring evaluations were taken in October, 1995, on all fruit from eye to knee level on the exterior of 15 randomly selected trees from each plot (30 trees per treatment). Typical scarring levels on outside fruit as sampled in this study are approximately twice as high as percent scarring of fruit sampled from the entire tree (inside fruit are less severally scarred). Scarring was rated as (a) none, (b) slight (any citrus thrips scarring), (c) severe (complete ring scar or extensive surface scarring at a level that would cause downgrading of fruit in a commercial operation). Economic scarring levels in a normal year are approximately 5% severe scars.