Abstract
The parasitoid wasp Aphelinus mali,Haldeman, 1851 (Hymenoptera: Aphelinidae) is the most important biological control agent against the woolly apple aphid, Eriosoma lanigerum (Hausemann, 1802) (Hemiptera: Aphididae), which is an important apple orchards pest throughout the world. Based on the importance of using low-risk compounds to protect beneficial agents, the present study was carried out to evaluate the toxic and repellent effects of two conventional chemicals (imidacloprid and thiacloprid) and coconut-derived biopesticide soap (PalizinÒ) toward A. mali. The results of residual bioassays on apple leaf discs indicated that imidacloprid after 24 h and insecticide soap after 72 h exposure time categorized at the highest and no/little toxicity rates, respectively. Ingestion bioassays on filter papers revealed that imidacloprid and thiacloprid had moderate toxicity rate, while insecticide soap had a low-level toxicity rate. Repellency test at Y-tube olfactometer showed that the repellent effects of both chemicals were more than that of insecticide soap. It is concluded that coconut-derived soap was compatible with the parasitoid activity, and the caution should be paid when including the two neonicotinoid insecticides imidacloprid and thiacloprid for E. lanigerum management.
Highlights
The woolly apple aphid (Eriosoma lanigerum (Hausemann, 1802), Homoptera: Aphididae) is important pest in apple orchards
Apple branches (‘Red Delicious’) infested with E. lanigerum were collected from apple orchards at Miami County (Semnan province, Iran) (36°N 55°E), in June 2016, and placed in one-liter flasks until emergence of the parasitoid wasps
Three commercial formulations of insecticides were used in the present study: imidacloprid concentrate suspension (Confidor®), provided as a commercial product by Paksame Iranian Company with 35 % active ingredient, thiacloprid (Calypso®) concentrate suspension, provided as a commercial product formulized by Bayer Company with 48 % active ingredient, and the coconut soap (Palizin®) as concentrate suspension was purchased from Iranian Kimia Sabzavar Company with 65 % active ingredient
Summary
The woolly apple aphid (Eriosoma lanigerum (Hausemann, 1802), Homoptera: Aphididae) is important pest in apple orchards. The woolly aphid parasitoid [Aphelinus mali Haldeman, 1851, (Hymenoptera: Aphelinidae)], is a specific and very efficient endoparasitoid of E. lanigerum that had been introduced from North America to other apple-growing regions of the world, such as in Iran (Heunis & Pringle, 2003, Su et al, 2017). Organic phosphorus insecticides, which are widely applied to reduce populations of E. lanigerum, cause severe damage in its parasitoid wasp populations (Beers et al, 2007). Acute toxicity of mineral oil and pyriproxyfen (a juvenile hormone mimic) was tested against the parasitoid wasp Aphytis melinus DeBach, 1959 (Aphelinidae). Mineral oil had high mortality on the adults of A. melinus, but pyriproxyfen had neither lethal nor sublethal effects. Parasitoid larvae were very susceptible to pyriproxyfen (Biondi et al, 2015)
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