Lacewings (Neuroptera: Hemerobiidae and chrysopidae) and integrated pest management: Enzyme activity as biomarker of sublethal insecticide exposure

Specific activities of head acetylcholinesterase (AChE) and whole body glutathione-S-transferase (GST) were assayed as biomarkers of sublethal exposure to insecticides in larvae of 2 lacewing species, the Chrysopid Chrysoperla carnea Stephens and the Hemerobiid Micromus tasmaniae Walker. When M. tasmaniae was exposed to the organophosphates methyl-parathion or azinphos-methyl, the rate of AChE-inhibition was toxin-specific, exponentially dose-dependent, and increased within 21 h of exposure. Activity of AChE was less inhibited in C. carnea larvae, which reflected its higher tolerance to organophosphates in mortality tests. No inhibition of AChE activity (e.g., resulting from nonspecific binding to the enzyme) was observed following treatment with the pyrethroid cypermethrin and the insect-growth regulators fenoxycarb, diflubenzuron, and tebufenozide. The activity of GST increased significantly in M. tasmaniae larvae treated with sublethal doses of cypermethrin and decreased significantly in larvae treated with fenoxycarb. In contrast, no changes in GST activity were observed in C. carnea larvae for any of the compounds tested. Inhibition of AChE in lacewings proved a useful tool to study the impact of different organophosphates used in integrated pest management. However, further investigations are necessary to evaluate the potential applicability of GST activity as a biomarker in lacewings as different results are likely for different lacewing species, varying exposure times, repeated dose levels, different-aged larvae, and different substrates for the enzyme reaction.