Toxicity and absorption of azadirachtin, diflubenzuron, pyriproxyfen, and tebufenozide after topical application in predatory larvae of Chrysoperla carnea (Neuroptera: Chrysopidae)

Abstract

Susceptibility of the generalist predator, the lacewing Chrysoperla carnea (Stephens), to the insect growth regulators azadirachtin, diflubenzuron, pyriproxyfen, and tebufenozide was tested in the laboratory. Third instars were topically treated with different doses of formulated materials of each compound by direct topical exposure. At maximum field-recommended dose, pyriproxyfen and tebufenozide were harmless to C. carnea, whereas azadirachtin and diflubenzuron were harmful (respective LD90s were 24.5 and 6.9 ng active ingredient [AI] per insect). At sublethal doses of azadirachtin and diflubenzuron, females laid fertile eggs, but azadirachtin caused a slight negative effect on oviposition. Pyriproxyfen and tebufenozide had no effect on oviposition and egg fertility. As a second approach of this study, toxicity data are discussed in relation to the rate of penetration and excretion after topical application. One hour after administration, ≈80% of pyriproxyfen had penetrated; whereas for diflubenzuron and tebufenozide, only percentages of 10-20% were recorded in the same time interval. However, although pyriproxyfen penetration was fast and high, most of the compound was also quickly eliminated via excretion. Our data suggest that the use of azadirachtin and diflubenzuron in combination with C. carnea in integrated pest management (IPM) programs should be carefully evaluated. Pyriproxyfen and tebufenozide are considered to be safe for C. carnea.