Characterization of the insecticidal properties of acetamiprid under field and laboratory conditions.

Abstract

Acetamiprid, a member of the neonicotinoid insecticide family, is a fairly new insecticide that has recently entered the market place. Its unique mode of action offers control against many important pests that had previously evolved resistant strains to most insecticides. Acetamiprid is very selective and provides outstanding control of sucking pests such as aphids and whiteflies without having detrimental effects on non-targets. Also, laboratory and greenhouse testing revealed acetamiprid's ovicidal activity against many pest species, including the bollworm, Helicoverpa zea (Boddie).

Field trials were conducted to evaluate the ovicidal properties of acetamiprid (Intruder 70WP) and other various neonicotinoids, against Helicoverpa zea (Boddie) under field conditions in Washington, Perquimans and Nash counties, North Carolina during 2001 and 2002. Newly laid (white) bollworm eggs were collected from cotton foliage within respective treatments at 0, 1, and 2 days after application and evaluated in the laboratory for ovicidal and eclosion mortality. During 2001, acetamiprid initially (0 day) provided mortality of bollworm eggs comparable to that obtained with two ovicide standards, thiodicarb and lambda-cyhalothrin. For eggs collected at one day after application, ovicidal activity of acetamiprid had declined more than that observed for the two standard ovicides; only the highest rate of acetamiprid provided comparable ovicide activity. There was no significant ovicidal activity with any of the insecticides for eggs deposited two nights after application (2 DAT). During 2002, the neonicotinoids acetamiprid, imidacloprid, and thiamethoxam provided mortality for eggs present on the plants at application (0 DAT), comparable to that obtained with thiodicarb and lambda-cyhalothrin. Mortality of eggs deposited the night after application and collected 24 hr after application (1 DAT) dropped precipitously in all insecticide treatments, except thiodicarb. Egg mortality at 1 DAT was comparable for all neonicotinoids. For eggs collected at two day after application, ovicidal activity of the neonicotinoids had ceased and egg mortality in the standard treatments had declined to ca. 25%. These studies confirmed ovicidal activity of all tested neonicotinoids under field conditions; however ovicidal activity of neonicotinoids was ephemeral and not comparable to that of the ovicide standards.

Comparative effects of various insecticide residues on populations of certain beneficial and pest arthropod species in cotton were examined in two field studies. Treatment effects were evaluated by population assessment through sweep net sampling at 1, 4, 7 and 14 days after application. Acetamiprid, spinosad, indoxacarb, and methoxyfenozide had no adverse impact on numbers of beneficial or pest species population levels when data were averaged over sampling dates and test locations. The lack of an observed treatment effect for any of the insecticides tested, particularly at 1 and 4 DAT, confirmed the selective toxicity profiles of the compounds.

Acetamiprid, imidacloprid, lambda-cyhalothrin, spinosad, and thiodicarb were evaluated to access their toxicity to preimaginal Trichogramma exiguum in a laboratory study and in a field study to determine the toxicity of residues on adult T. exiguum. Lambda cyhalothrin and spinosad caused very high mortalities of preimaginal T. exiguum when applied to host eggs; imidacloprid caused intermediate mortality, and acetamiprid and thiodicarb were not toxic. Acetamiprid was the only insecticide that was not toxic to T. exiguum adults when exposed at 1 DAT to residues on leaves of treated cotton plants in the field. None of the insecticides were toxic to adult T. exiguum at 6 DAT under field conditions.