Physiological Entomology (2006) DOI: 10.1111/j.1365-3032.2006.00525.x © 2006 The Authors Journal compilation © 2006 The Royal Entomological Society 1 Sub-lethal responses of the large pine weevil, Hylobius abietis, to the pyrethroid insecticide lambda-cyhalothrin D. ROSE, G. A. MATTHEWS and S. R. LEATHER Division of Biology, Imperial College London, Silwood Park Campus, Ascot, U.K. Abstract. The response of the large pine weevil ( Hylobius abietis) to the pesticide lambda-cyhalothrin, a pyrethroid, is investigated. Both behavioural (feeding prefer- ences) and nutritional and physiological (lipid content) responses are recorded. Hylobius abietis shows both a significant avoidance of pesticide-treated food sources and a decrease in lipid content after exposure, but a full recovery after feeding on untreated food. It is proposed that the mechanism for the pesticide avoidance and altered lipid levels is due to an anti-feedant effect of the pesticide. Implications for pest management programmes are described. Key words. Hylobius abietis, insecticide recognition, lambda-cyhalothrin, Sitka spruce, pyrethroids. Introduction Hylobius abietis Linnaeus (Coleoptera: Curculionidae) can typically cause 30–100% mortality of transplanted Sitka spruce ( Picea sitchensis Bong) saplings in the absence of in- secticide treatment (Heritage et al., 1989) and is one of the most destructive pests of European and Scandinavian forestry (Leather et al., 1995, 1999; Orlander et al., 2000). For this rea- son, the Forestry Commission in the U.K. uses prophylactic insecticide treatment. This has typically been applied using either the electrodyn spray-conveyor system (an electrostatic device that creates a static charge to attract a droplet towards a target) or by dipping the shoot and upper stem in a vat of the insecticide permethrin (Stoakley & Heritage, 1990; Heritage, 1996). These treatments are applied in the nursery before the saplings are transplanted. The applied insecticide gives one to two seasons protection from damage by H. abietis and also by the less damaging Hylastes spp. (Coleoptera: Scolytidae) (Heritage, 1997). Prophylactic treatment avoids the necessity of spraying nontarget areas and therefore some of the poten- tially hazardous effects of insecticide use. Previous work has shown that H. abietis have a strong ability to select for food sources that are not treated with in- secticides (Rose et al., 2005). However, in these experiments, Correspondence: S. R. Leather, Division of Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, U.K. Tel.: +44 (0) 20759 42316; fax: +44 (0) 20759 42339; e-mail: s.leather@imperial.ac.uk the Sitka spruce or Scots pine saplings ( Pinus sylvestris) were uniformly treated, with the majority of the surface be- ing sprayed with insecticide. Typically saplings treated in the field are unlikely to be completely covered by insecticide be- cause side branches may impede deposition of insecticide on the main stem. In these situations, it is important to know whether H. abietis is able to detect the treated and untreated patches, or if a small treated zone is enough to deter the in- sect from feeding. It has been reported for other beetles, no- tably Rhyzopertha dominica, that uneven insecticide coverage does not reduce the overall effectiveness of control (Muda & Cribb, 1999). However, this was for a stored grain pest and a minimum of 50% coverage was still required. Sub-lethal effects of insecticides on insects range from re- duced foraging activities due to increased grooming, hyper- activity with no repellency, decreased fecundity and delays in development or emergence from larval stages (Wiles & Jepson, 1994; Leather, 1995; Liess & Schulz, 1996; Alzogaray & Zerba, 2001; Epstein et al., 2001). Anti-feedant effects may be due to a stomach action of the insecticide, through a repellant action or by interruption of other behaviours lead- ing to the prevention of feeding (Armstrong & Bonner, 1985; Gerard et al., 1999). Anti-feedant effects on insects are reported for a variety insecticides, including pyrethroids (Tan, 1981; Armstrong & Bonner, 1985; Dobrin & Hammond, 1985; Eidmann et al ., 1996). Similar effects are shown with some other chemicals, such as limonene and Neem against H. abietis (Mukherjee & Sharma, 1996; Ibrahim et al ., 2001). The