ISHS Acta Horticulturae 470: II International Symposium on Pistachios and Almonds
EFFECTS OF PYRETHROID INSECTICIDE RESIDUES ON ALMOND LEAVES ON THE BIOLOGY OF THE WESTERN ORCHARD PREDATOR MITE GALENDROMUS OCCIDENTALIS (NESBITT) (ACARI: PHYTOSEIIDAE) |
| Authors: | D. B. Walsh, Frank G. Zalom, M. Stimmann |
| Keywords: | pyrethroid insecticides, esfenvalerate, permethrin, predators, residue, almonds, Galendromus occidentalis |
| Abstract:
Residue analysis of leaves collected in late fall from almond trees treated with maximum label rates of permethrin or esfenvalerate at hullsplit in early summer yielded 0.130 ng/mm2 and 0.987 ng/mm2 of permethrin or esfenvalerate, respectively. In laboratory studies, leaf disks were dipped in one of six glycol-based spreader solution containing a range permethrin or esfenvalerate concentrations. These treatments resulted in residual levels of permethrin ranging from 0.0087 to 14.30 ng per mm2. Residual esfenvalerate concentrations ranged from 0.006 to 5.26 ng per mm2. The western orchard predator mite Galendromus occidentalis (Nesbitt) (Acari: Phytoseiidae) was chosen for bioassay of the effect of pyrethroid residues. Five gravid adult females were placed on treated leaf disks and evaluated 72 h following treatment for changes in behavior, mortality, and fecundity in comparison with controls treated solely in a glycol-based spreader solution. G. occidentalis exhibited distressed behaviors and were significantly (p<0.05) repelled by esfenvalerate at all observed residue levels, and by permethrin at all residue levels exceeding 0.042 ng/mm2. Significant mortality was observed at 72 h compared to the controls at all residue levels of esfenvalerate (F= 21.6, p< 0.01) and all residue levels of permethrin exceeding 0.039 ng/mm2 (F=36.1, p<0.01). Fecundity of surviving G. occidentalis was significantly reduced at residue levels exceeding 0.057 ng/mm2 for esfenvalerate and 0.039 ng/mm2 for permethrin, concentrations substantially below those measured on field samples collected in mid-November, 5 months after the insecticides were applied in mid-June. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
