Timing Lorsban Applications For California Red Scale Control, 1985

Abstract

Abstract A randomized complete block experiment with 10 lingle-tree replicates and 5 treatments was conducted in a field of 11-year old Lisbon lemons at the University of California Lindcove Field Station, Exeter, CA, Pretreatment densities of California red scale (CRS) were evaluated in mid-Apr, 1985 by examining in each plot, 75 9-inch twigs from the previous growth flush. Each twig was scored in situ as being infested or not infested with live CRS. Plots were assigned to blocks on the basis of pretreatment CRS density and the treatments were assigned randomly to each block. The 5 treatments were 5 different times for application of an identical amount of Lorsban 4E (% pt/100 gal applied by handguns from both ground and tower positions at ca. 520 psi, and ca. 20 gal/tree). Maximum and minimum temperatures recorded at the Lindcove Field Station were used to calculate degree days for CRS development (lower threshold = 53°F, no upper threshold) and pheromone traps were used to monitor male flight. Posttreatment samples were taken in mid-Oct, 1985 and in mid-Mar, 1986 by in situ examination in each plot of 75 9-inch twigs in Oct, 100 3-inch twigs in Mar, and 100 fruit in both posttreatment samples. Twigs were scored as infested or not infested with live CRS. Each fruit was scored as having 0, 1-10, or >10 live and/or dead CRS since fruit are downgraded in the packinghouse when infested with large numbers of live or dead scale. Therefore, counts of live and dead scale on fruit were used to assess how well the treatment protected the fruit from becoming infested and being downgraded, while counts of live scale on twigs were used to assess how well a treatment suppressed population growth.