This study investigated the effects of the Pymetrozine 50WG (PY) and Thiamethoxam 25WG (TH) on the cotton aphid parasitoid Aphelinus gossypii Timberlake (Hym.: Aphelinidae) and on the whitefly predator Delphastus pusillus (LeConte) (Col.: Coccinellidae). Cotton leaves containing mummies of A. gossypii were collected and treated with 75, 150, 250, 350, 450, 550 and 650 mg a.i. PY/L, and with 3.9, 7.8, 15.6, 31.25, 62.5, 125, and 250 mg a.i. TH/L. Mummies were individualized at spray time and at day 4 after spraying. Parasitoid emergence was not affected by PY and ranged from 59.9 to 75%, while it was inversely proportional to TH concentrations and ranged from 30.2 to 69.6%. Treated cotton leaves with PY and TH were collected 3h, 3 and 6 days after spraying and colonized with adults and 4th/5th-instar larvae of D. pusillus in the laboratory. Mortality was scored after 24h. Predators released on TH treated leaves experienced mortality from 70 to 100%, except for larvae released at day 6 after spraying time that had mortality from 48.1 to 63%. Predators released on PY treated leaves showed no mortality or <20%. Topical toxicity for both insecticides was studied on larvae, pupae and adults of D. pusillus. The percentage of adults living yielded after 6 days on leaves treated and infested with larvae, pupae and adults of D. pusillus were 100, 77, 100 and 69.6% under PY treatment, and 97.4, 2.7, 8.7 and 8.3% under TH treatment.
Species 1: Hymenoptera Aphelinidae Aphelinus gossypii (cotton aphid parasitoid)
Species 2: Coleoptera Coccinellidae Delphastus pusillus (whitefly predator)
Keywords: selectivity of insecticides, biological control
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