02363nas a2200193   4500008004100000020001400041245013300055210006900188260001100257300001200268490000800280520163700288653002301925100002201948700002201970700001801992700002402010856013502034       2009                        eng d  a0931-204800aDeltamethrin-induced feeding plasticity in pyrethroid-susceptible and -resistant strains of the maize weevil, Sitophilus zeamais0 aDeltamethrininduced feeding plasticity in pyrethroidsusceptible   cAugust  a524-5320 v1333 aPhenotypic plasticity contributes to the adaptative evolution of populations exposed to new or altered environments. Feeding plasticity is a component of phenotypic plasticity not usually considered in insect strains adapted to insecticide-altered environments, but which may either accentuate or mitigate insecticide resistance. This is a concern in the pyrethroid-resistant strains of the maize weevil Sitophilus zeamais Motsch. (Col., Curculionidae), and the reason for this study. A pyrethroid-susceptible and two pyrethroid-resistant strains of maize weevil were subjected to free-choice and no-choice tests with maize grains sprayed with increasing doses of the pyrethroid, deltamethrin. The insects from the pyrethroid-resistant strains exhibited higher feeding avoidance with increased deltamethrin doses than insects from the susceptible strain when subjected to free-choice tests. The strains of maize weevil physiologically resistant to pyrethroids were also behaviourally resistant to deltamethrin [long dash] an additional management concern. The resistant strains avoid deltamethrin-sprayed grains and are less nutritionally affected by this compound, with divergent responses from the susceptible strain with increased doses of deltamethrin. Furthermore, the higher relative growth rate and consequently higher efficiency of food conversion observed in the insecticide-resistant strains were significant even without insecticide exposure, indicating that these traits are stimulus-independent and may persist even without further insecticide selection, potentially limiting the options available for their management.10aSitophilus zeamais1 aGuedes, N., M. P.1 aGuedes, R., N. C.1 aSilva, L., B.1 aCordeiro, E., M. G.  uhttps://weevil.myspecies.info/deltamethrin-induced-feeding-plasticity-pyrethroid-susceptible-and-resistant-strains-maize-weevil-si02659nas a2200205   4500008004100000020001400041245011700055210006900172260000800241300001400249490000700263520191900270653002402189100001902213700002302232700002402255700001802279700002202297856013402319       2011                        eng d  a0261-219400aInsecticide resistance, mixture potentiation and fitness in populations of the maize weevil (Sitophilus zeamais)0 aInsecticide resistance mixture potentiation and fitness in popul  cDec  a1655-16660 v303 aHigh levels of pyrethroid resistance and emerging organophosphate resistance in Brazilian populations of the maize weevil Sitophilus zearnais (Coleoptera: Curculionidae) led to the registration of esfenvalerate + fenitrothion against them. Thus, a survey of physiological and behavioural resistance was carried out in 27 insect populations for two pyrethroids, esfenvalerate and permethrin, and the esfenvalerate + fenitrothion mixture. Physiological resistance to fenitrothion was also assessed, as was the potentiation of the mixture. The potential fitness cost associated with insecticide resistance was also investigated. The resistance levels were low to fenitrothion (<14.1-fold), low to moderate to the pyrethroids (1.6-70.0-fold) and low to the pyrethroid-organophosphate mixture (<5-fold) with a high heterogeneity of response among populations. The potentiation of insecticidal activity achieved with the insecticide mixture was very high (>350-fold) reinforcing its usefulness for managing weevils. There was little variation in walking behaviour (and insecticide avoidance) among populations: there was no significant variation in fitness, body mass and respiration rate among the populations of the insect. These however, displayed variable rates of grain consumption and activity of amylase and lipase. A decrease in insecticide resistance in maize weevil populations was observed relative to previous studies, but with an initial development of resistance to the insecticide mixture. Behavioural and physiological resistance were not correlated and not associated with fitness cost. Our results support the use of esfenvalerate + fenitrothion against the maize weevil, which is likely to have reduced the levels of pyrethroid resistance in field populations. However, resistance to this mixture seems to be evolving, justifying concerns regarding its use. (C) 2011 Elsevier Ltd. All rights reserved.10aSitophilus zearnais1 aCorrea, A., S.1 aPereira, E., J. G.1 aCordeiro, E., M. G.1 aBraga, L., S.1 aGuedes, R., N. C.  uhttps://weevil.myspecies.info/insecticide-resistance-mixture-potentiation-and-fitness-populations-maize-weevil-sitophilus-zeamais