Effects of neonicotinoids on adult and immature Drosophila suzukii in the laboratory and in an experimental blueberry field

Charles Clark Coslor

The lethal and sublethal effects of four neonicotinoid insecticides on different life stages of Drosophila suzukii were examined. In the laboratory, adult flies were exposed to residues and topical applications of acetamiprid, dinotefuran, imidacloprid, and thiamethoxam to assess toxicity. In another study, females were allowed to oviposit on blueberries dipped in the four neonicotinoids and the effects on egg and larva survivorship and oviposition were examined. Field studies were conducted to test translaminar and systemic uptake of neonicotinoids into blueberry fruit for D. suzukii suppression. Ground applications of dinotefuran and imidacloprid were applied to ‘Elliott’ blueberry bushes with a backpack sprayer and laboratory females were allowed to oviposit on sampled berries. Acetamiprid, dinotefuran, and imidacloprid were injected into drip irrigation to assess systemic uptake into ‘Bluecrop’ and ‘Elliott’ blueberry bushes. Berry samples were exposed to females and the effects of neonicotinoids on egg and larva survivorship and oviposition were examined to assess systemic uptake into the fruit. Leaf and berry samples were sent to a commercial laboratory to quantify insecticides in the treated blueberry bushes. Results showed that residues and topical applications of neonicotinoids are toxic to D. suzukii but not at acceptable levels for pest management. Females are more tolerant to neonicotinoid residues than males. The neonicotinoids acetamiprid, dinotefuran, and imidacloprid suppressed oviposition when applied to berries. Neonicotinoids reduced the survivorship of eggs and larvae in laboratory studies. In the field, ground applications did not have the same effects as in the laboratory, and no significant differences were found that suggested oviposition deterrence, ovicidal or larvicidal effects. Results of the chemigation bioassays revealed that there was no oviposition deterrence, ovicidal or larvicidal activity in berries sampled from treated blueberry bushes. Results of the commercial laboratory tests confirmed that there was no uptake of neonicotinoids into the berries but uptake of imidacloprid and dinotefuran into the leaves of treated bushes did occur. These findings show that neonicotinoids will reduce D. suzukii infestations in the laboratory though implementation may be impractical. Neonicotinoid chemigation may be a useful tactic for controlling arthropod pests that feed on blueberry vegetative tissue.

Effects of neonicotinoids on adult and immature Drosophila suzukii in the laboratory and in an experimental blueberry field

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