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Secondary transmission of fipronil toxicity between Oriental cockroaches Blatta orientalis L in arenas
Author(s) -
le Patourel Geoff
Publication year - 2000
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/1526-4998(200009)56:9<732::aid-ps206>3.0.co;2-f
Subject(s) - nymph , biology , toxicity , instar , toxicology , cockroach , zoology , fipronil , veterinary medicine , botany , pesticide , ecology , larva , medicine
Mixed colonies of adult male and female Oriental cockroaches were conditioned to a 12:12 h photocycle in arenas (0.23 m 2 ) with a harbourage, food and water and then exposed to deposits (30 mg or 2 × 30 mg) of 0.5 g kg −1 fipronil gel bait at the beginning of a dark phase. The bait was rapidly consumed by the first sub‐group of insects to emerge from the harbourage; any residual bait was removed from the arenas 4 h into the following light phase. Third‐instar nymphs were then introduced and mortality was monitored over the subsequent 14 days with all cadavers left in situ . Death of cockroaches under these conditions was due to direct poisoning of the sub‐group of the adults that consumed the bait and to secondary transfer of toxicity to the remainder of the adult and to the nymphal populations. Mean mortality in the adult populations increased to > 96% (females) and > 53% (males) with consistently higher mortality of females than males; that in the third‐instar nymph (unexposed) populations increased to 25–50%. Some cadavers were wholly or partially eaten by other cockroaches during this period, and this was interpreted as the major mechanism of secondary transfer of toxicity. Individual adult females were fed weighed bait deposits (10 mg) and, following death (24 h), the cadavers were transferred to closed containers held at 33%, 52% or 76% relative humidity /28 °C for periods of up to 7 weeks. They were then added individually to groups of five adult females provided with water but no alternative food source. Mean mortalities (>64% at 1 week and > 96% at 7 weeks) were not significantly lower than mean mortalities produced by freshly poisoned cockroaches, showing that no loss in the insecticidal activity of the cadavers occurred under these storage conditions. The potential of necrophagy to supplement the primary action of fipronil bait treatment of Oriental cockroach infestations by inhibiting colony redevelopment is discussed. © 2000 Society of Chemical Industry