Susceptibility of the leaf-eating beetle, Galerucella calmariensis, a biological control agent for purple loosestrife (Lythrum salcaria), to three mosquito control larvicides.

We evaluated the susceptibility of Galerucella calmariensis, a species used to control purple loosestrife (Lythrum salicaria), to three mosquito control larvicides. Larvae and adults were fed loosestrife cuttings dipped in Abate (< or = 375 g x L(-1)), Altosid (< or = 250 g x L(-1)), and Bacillus thuringiensis var israeliensis (Bti) (< or = 110 g x L(-1)). Eggs on cuttings were dipped in the same concentrations. Pupae were immersed in Abate and Altosid solutions (< or = 474.4 microg x L(-1) and < or = 1,169.2 microg x L(-1), respectively). Hatching success of eggs dipped in Abate (> or = 3.75 g x L(-1)) was reduced significantly and survival was significantly lower among larvae and adults eating cuttings dipped in Abate (> or = 0.17 g x L(-1) and > or = 2.27 g x L(-1), respectively). Hatching success of eggs dipped in Altosid (> or = 2.52 g x L(-1)) was reduced significantly. With exposure to Altosid, larval survival to pupation and adult emergence was reduced significantly at concentrations of > or = 2.92 g x L(-1) and > or = 0.63 g x L(-1), respectively. Altosid (> or = 0.23 g x L(-1)) also delayed the onset of pupation and adult emergence among larvae that survived to pupate. Larvae that survived with exposure to Altosid (> or = 1.72 g x L(-1)) grew to 70% larger than those exposed to lower concentrations. Pupal survival was unaffected with exposure to Abate and Altosid and adult survival was unaffected with exposure to Altosid. Bacillus thuringiensis var israeliensis did not adversely affect any life stage of G. calmariensis. The mean Abate concentration on cuttings exposed to operational spraying was in the range that reduced egg hatchability and adult survival but was higher than concentrations that caused complete mortality of larvae. The mean Altosid concentration on cuttings exposed to operational spraying was in the range that reduced hatching success in eggs and delayed pupation and adult emergence of larvae.