California Red Scale Pesticide Efficacy Trials, 1994
Abstract Efficacy of two insect growth regulators (IGR) for the control of California red scale (CRS) were compared to an organophosphate insecticide. Additionally, the effects of the treatments on parasitism by Aphytis melinus and Comperiella bifasciata were evaluated. Insecticides were applied to CRS infested 11 yr old ‘Washington navel’ orange trees at the Lindcove Research and Extension Center, Exeter, California. Seven treatments included a water control, Supracide 2E applied once, CGA 59205 (an IGR) applied once at 20.0 gm(ai), and applied twice at 30.0 gm(ai), S-71639 (an IGR) applied twice both alone and in combination with 0.5% Volck Supreme Spray oil, and 0.5% Volck Supreme Spray oil applied twice. Treatments were assigned based on laboratory evaluation of population densities of live 1st and second instar males and females as well as third instar and gravid females on five randomly selected twig samples (2nd year growth) per tree. Treatments were applied to single trees and replicated 10 times. All treatment applications were timed for emergence of 1st generation CRS crawlers; four of the treatments were reapplied when the 2nd generation of crawlers emerged. Insecticides were applied on 12-13 May and 19 Jul with a Bean hand-sprayer at 450 psi and approximately 1000 gpa (11-12 gal/tree). After treatment, twig samples were evaluated in the same manner as the pretreatment samples. Additionally, we evaluated scale densities on five randomly selected fruit per tree. Sample collections were completed at approximately 30 d intervals after the first treatment. Pretreatment sampling was conducted on 13 Apr. Post treatment counts were conducted on twigs on 13 Jun and 12 Jul and both twigs and fruit on 17 Aug, and 27 Sep. We evaluated the percentage of fruit infested with >10 CRS per fruit in each of the treatments at harvest on 6-7 Dec. Concurrently we determined the percentage of parasitism by A. melinus and C. bifasciata of scale on fruit by evaluating live CRS for the presence of the parasitoids or evidence of host feeding by A. melinus.