Principles of insecticide resistance management

La demande pour des stratégies efficaces de gestion de la résistance se fait de plus en plus pressante, au fur et à mesure que le nombre d'espèces résistantes aux insecticides augmente mondialement alors que les ressources insecticides diminuent. Les perspectives de développement de telles stratégies sont accrues par les développements récents en biochimie, en génétique moléculaire, en écologie, en dynamique, en dépistage et dans d'autres aspects importants de la résistance. Les approches généralement reconnues pour la gestion de la résistance sont regroupées en trois catégories principales: une pression de sélection faible, complétée par une composante élevée de mesures non-chimiques (gestion par modération); l'élimination de l'avantage sélectif des individus résistants en augmentant l'absorption des insecticides par l'utilisation d'attractifs, ou en supprimant les enzymes de detoxication par l'utilisation de synergistes (gestion par saturation); l'application d'une sélection multi-directionnelle au moyen de mélanges ou de rotations d'insecticides non-apparentés ou par l'utilisation d'insecticides à plusieurs sites d'action (gestion par attaque multiple). Ces approches ne sont pas mutuellement exclusives et des éléments de chacune peuvent être utilisés pour la formulation d'un programme saisonnier de gestion. La stratégie choisie doit être basée sur une connaissance approfondie des effets sur la résistance des insecticides envisagés, et de la biologie et de l'écologie des espèces concernées, et elle doit utiliser toutes les méthodes de lutte non-chimiques disponibles.The need for effective strategies in resistance management is becoming more pressing as the number of insecticide-resistant species continues to increase worldwide while insecticide resources are diminishing. Prospects for development of such strategies are enhanced by recent advances in knowledge on the biochemistry, molecular genetics, ecology, dynamics, monitoring, and other important aspects of resistance. The generally recognized approaches to resistance management are grouped under three principal categories: first, low selection pressure, supplemented by a strong component of non-chemical measures (management by moderation); second, elimination of the selective advantage of resistant individuals by increasing insecticide uptake through the use of attractants, or by suppressing of detoxication enzymes through the use of synergists (management by saturation); and third, application of multi-directional selection by means of mixtures or rotations of unrelated insecticides or by use of chemicals with multi-site action (management by multiple attack). These approaches are not mutually exclusive and elements from each can be used to formulate a season-long management program. The strategy chosen must be based on a thorough knowledge of the resistance implications of the candidate insecticides and of the biology and ecology of the species concerned, and must make use of all available non-chemical control measures

A discrete host-parasitoid model with development of pesticide resistance and IPM strategies

The development of pesticide resistance significantly affects the outcomes of pest control. A quantitative depiction of the effects of pesticide resistance development on integrated pest management (IPM) strategies and pest control outcomes is challenging. To address this problem, a discrete host-parasitoid model with pesticide resistance development and IPM strategies is proposed and analyzed. The threshold condition of pest eradication which reveals the relationship between the development of pest resistance and the rate of natural enemy releases is provided and analyzed, and the optimal rate for releasing natural enemies was obtained based on this threshold condition. Furthermore, in order to reduce adverse effects of the pesticide on natural enemies, the model has been extended to consider the spraying of pesticide and releases of natural enemies at different times. The effects of the dynamic complexity and different resistance development equations on the main results are also discussed

Resistance of Brazilian diamondback moth populations to insecticides

Plutella xylostella is a recurring pest on cruciferous crops around the world. In Brazil, it typically requires large number of insecticide sprays, which may lead to fast evolution of resistance. The aim of this study was to assess the susceptibility of Brazilian diamondback moth populations to the insecticides abamectin, deltamethrin, and spinosad. Leaf dip bioassays were used to determine mortality data obtained after 48 h of exposure to insecticides and subjected to Probit analysis. The population from Bonito, state of Pernambuco, Brazil, had the highest toxicity ratio (20.2 - fold) to abamectin compared to the reference population. The LC50 values for deltamethrin ranged from 85.2 to 360.1 mg L-1, demonstrating a high survival of populations in relation to this insecticide field dose rate (7.5 mg L-1). The toxicity ratios of the estimated LC50s, however, were very low (varying from 2.2 - to 4.2 - fold). Most populations exhibited toxicity ratios for spinosad, ranging from 2.3 - to 5.1 - fold, while both the LC50 and LC95 values reflected a high susceptibility to the spinosad field dosage (120 mg L-1). Only the Bonito - PE population resisted to abamectin, while all P. xylostella populations were resistant to deltamethrin, but particularly susceptible to spinosad because of the absence of selection pressure with it in these areas.Plutella xylostella é uma praga recorrente em brássicas de todo o mundo. No Brasil, normalmente exige grande número de pulverizações de inseticidas, que pode levar à rápida evolução da resistência. Avaliou-se a suscetibilidade de populações brasileiras da traça das crucíferas aos inseticidas abamectina, deltametrina e espinosade. Bioensaios de imersão de folhas foram utilizados para determinar a mortalidade, sendo os dados obtidos após 48 h de exposição aos inseticidas e submetidos à análise de Probit. A população de Bonito-PE apresentou a maior razão de toxicidade (20,2 vezes) para abamectina em relação à população de referência. Os valores de CL50s para deltametrina variaram entre 85,2 - 360,1 mg L-1, demonstrando alta sobrevivência das populações a este inseticida com relação à dose de campo (7,5 mg L-1). Entretanto, as razões de toxicidade das CL50 estimadas foram muito baixas (variando de 2,2 a 4,2 vezes). A maioria das populações apresentou razões de toxicidade para espinosade, variando de 2,3 para 5,1 vezes, embora os valores de CL demonstram alta suscetibilidade delas à dose de campo para espinosade (120 mg L-1). Apenas a população de Bonito PE apresentou resistência a abamectina, enquanto todas as populações de P. xylostella estão resistentes a deltametrina, mas suscetíveis ao espinosade particularmente devido à ausência de pressão de seleção com este nestas áreas

Variation in organophosphate resistance and esterase activity in Culex quinquefasciatus Say from California

International audienc

Prevention of changes in the electrophoretic mobility of overproduced esterases from organophosphate-resistant mosquitos of the Culex pipiens complex

International audienc