California Citrus Thrips Small Plot Trial, 1997

Abstract

Abstract Insecticides were evaluated for control of citrus thrips during spring, 1997 in Field 12 (27-year-old ‘Atwood’ navel oranges) at the University of California’s Lindcove Research and Extension Center near Exeter, California. The majority of pesticides were applied to trees with a Bean hand-sprayer at 500 psi, outside coverage, approximately 200 gpa. One treatment was applied to the soil: the Metasystox-R soil treatment was applied by pre-watering trees for 2 hours, applying the chemical in 1 gallon of water to the area between 2 trees wetted by drippers, and post-watering for an additional 4 hours (Bowsmith emitters, 2 under each tree, 10 gallons of water per hour per emitter). Field 12 was divided into 4 contiguous blocks of 96 trees and 24 treatments were applied with one replicate of each treatment assigned randomly to each block; each replicate included four contiguous trees. Citrus thrips fruit scarring evaluations were done early September on all fruit of 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 a 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.