PACIFIC SPIDER MITE CONTROL IN ALMOND, 2005
Arthropod Management Tests
Pacific spider mite: Tetranychus pacificus McGregor The year 2005 was recognized as one of the worst mite years in recent history for spider mites in almonds in the lower San Joaquin Valley, CA. Defoliation of almond orchards by spider mites was a widespread phenomenon across many locations farmed by many growers. This experiment was conducted during the late summer during 2005 in a 1-yr-old commercial block of almonds located in western Kern County, CA. We did a visual survey of trees in an
... y of trees in an area of approximately 2 acres and chose the 85 most heavily-infested trees. These trees were randomly assigned to one of five replicates each of 14 miticides with or without oil, oil alone, a water check, and an untreated check. Miticides were applied on 12 Aug 2005 with a CO 2 powered backpack sprayer. Some treatments included 1% 415 narrow range petroleum oil. Applications were made at 30 psi using an 8002 fan jet nozzle. The spray solution was prepared by mixing the miticides to a 200 gpa dilution and then spraying each individual tree with 500 ml of that solution, providing coverage that ranged from good coverage (leaf surface completely or close to completely damp) to slight runoff. At the time of application it was > 100°F, the leaves were hardened off and dusty, and there was a large amount of spider mite webbing covering many of the leaves. Mite populations were evaluated one day prior to treatment on 11 Aug and then again 3 DAT (15 Aug), 7 DAT (19 Aug), 14 DAT (26 Aug), and 21 DAT (2 Sep). On each evaluation date, 10 leaves were randomly collected from each tree. Leaves were placed into small paper bags, placed in a cooler, and evaluated under a scope in the lab for the total number of Pacific spider mite eggs and motiles (juveniles + adults). Mean no. motiles and eggs/leaf were calculated for each treatment. These data were transformed using squareroot (x) and analyzed by ANOVA with means separated by Fisher's Protected LSD at P ≤ 0.05. Data are presented as untransformed means. Under these sub-optimal conditions of heavy mite pressure with hardened off, webbed over leaves under temperature conditions over 100°F., several newer miticides, including Kanemite, Zeal, Envidor + Oil, both rates of Onager, Fujimite, and Acramite controlled Pacific mite well. The least effective of the miticides were the two abamectin products (Agri-Mek and A-8612), which are best known for their effectiveness prior to when leaves harden off.