Sublethal effects on reproduction and biomarkers by spinosad and indoxacarb in cockroaches Blattella germanica

摘要

The present project investigated effects of two insecticides, the naturalyte spinosad and the oxadiazine indoxacarb, against adults of the cosmopolitan pest insect Blattella germanica (L.). At 6 days after topical treatment on newly moulted adults, the median lethal dose (LD50) was 429 ng/insect for spinosad and 51 ng/insect for indoxacarb, indicating that indoxacarb was more active than spinosad. Both treatments showed a cessation of feeding, followed by paralysis and death. In continuation, surviving adults showed a reduced reproduction with a significant reduction in numbers of oocytes, in basal oocyte volume, and in numbers of laid and hatched eggs per ootheca. In parallel, we determined the biomarkers acetylcholinesterase (AChE), lactate deshydrogenase (LDH), glutathione S-transferase (GST) and glutathione (GSH) upon treatment. For both spinosad and indoxacarb, AChE and GSH were reduced, while LDH and GST were increased. The data are discussed in relation to insecticide use, sublethal effects, chemical stress and metabolism.