Speed-Sprayer Trials for Citrus Thrips Control, 1997

Abstract

Abstract Insecticides were evaluated for control of citrus thrips during spring, 1997 in Field 41-42 (13-year-old ‘Washington’ navel oranges) at the University of California’s Lindcove Research and Extension Center near Exeter, California. Pesticides were applied with an FMC CP-267 speed-sprayer pulled behind a tractor. Five treatments were compared against an untreated control using 200 gpa and outside coverage (achieved by reducing fan speed). The field was divided into 12 plots; treatments were assigned to plots randomly and were replicated twice in each field; each plot was six rows wide and 5-8 trees long. Ten data trees were chosen from the center two rows of each plot, excluding the trees at the end of a row. Citrus thrips infestation due to first- and second-instar immatures was monitored after petal fall by examining 5 fruit randomly selected from each data in each plot (50 fruit per plot, 100 fruit per treatment). Citrus thrips fruit scarring evaluations were taken in September on all fruit on the exterior of data trees from knee to eye level. 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 severely scarred). Scarring was rated as: (a) none, (b) slight (any citrus thrips scarring), or (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.