Citrus Thrips Control and Impact on California Red Scale, 1989

Insecticides for control of CT were evaluated during spring, 1989 on 5-year-old “Old Line” ‘Washington navel’ orange trees in Field 41-42 located at the University of California, Lindcove Field Station near Exeter, California. The effect of these treatments on CRS also was evaluated. One hundred-ten single tree plots were assigned to 10 blocks (11 trees per block) based on pretreatment levels of CRS so that the 11 trees per block had similar pretreatment infestations of CRS. One tree in each block then was assigned randomly to each of the 11 treatments. Thus, the experimental design for CRS data was a randomized complete block with 10 blocks which was analyzed by 2-way ANOVA. However, the criterion for blocking (scale infestation) was irrelevant to thrips populations, therefore, the thrips data were analyzed by 1-way ANOVA with 10 replicates. There were 11 treatments: an untreated control and two types of spray coverage for each of 5 insecticides. “Scale” spray coverage was high volume (ca. 1,000 gal/acre) with the objective of wetting all interior and exterior woody and foliar surfaces. This is a type of coverage used to control CRS. “Thrips” coverage was low volume (200 gal/acre) with the objective of obtaining outside coverage (i.e. wetting the exterior of the tree only).