Citricola Scale Insecticide Efficacy Trial, 1996

Insecticides alone and in combination with a spray adjuvant were evaluated against the lst-instar nymphal stage of citricola scale on citrus compared with a water application. Treatments were applied to 22-year-old ‘Washington’ navel orange trees at the Lindcove Research and Extension Center, Exeter, California. The first application was made 16 Sep 1996 and was timed to cause mortality of 1st-instar nymphs on leaves. A separate application of Lorsban was applied 14 Nov 1996 and targeted lst-instar nymphs after they had begun to move to the twigs. The purpose of testing this later application was to determine if a late spray of a low rate of Lorsban could be efficacious against citricola scale. Growers utilizing an integrated pest management program would like to minimize the negative impact of Lorsban application on parasitism of California red scale by Aphytis melinus. Eight replications of single tree treatments were applied at 300 gpa (3-4 gal/tree), 300 psi using a Bean handsprayer. On 4 Sep and 25 Oct 1996, treatments were evaluated by collecting 10 leaves from the northeast quadrant of each tree and counting the number of live lst-instar nymphs. The following spring, 2 May 1997, citricola scale densities were evaluated by counting the number of life female citricola scale on 10 twigs (approximately 30 cm in length) per tree in each treatment.