California Citrus Thrips Pesticide Efficacy Trial, 1992

Insecticides for the control of citrus thrips were evaluated spring, 1992 in Field 12 (22-yr old Atwood ‘navel’ oranges) located at the University of California’s Lindcove Field Station near Exeter, Calif. Pesticides were applied 28, 29 Apr or 11, 12 May with a Bean hand-sprayer at 500 psi, outside coverage, approximately 200 gal/acre. The field was divided into 4 blocks with one replicate of each treatment allocated randomly within each block; each replicate consisted of four trees (except one replicate in treatment 24 had three trees). Citrus thrips fruit scarring evaluations were taken in Oct, 1992 on all fruit on the exterior of the tree 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 (approximately 10% severe scarring of outside fruit as sampled in this study). In 1992, late Apr and May were relatively warm. Daily maximums were between 79 and 95°F (mean of 87.4°), mean average temperature of 73.7°, in the 4 weeks after petal-fall. A little precipitation occurred (0.04 inch on both 1 May and 6 May; 0.08 inch on 30 Jun) but probably had little effect on the treatments.