Climate warming is expected to impact the response of species to insecticides. Recent studies show that this interaction between insecticides and temperature can depend on other factors. Here, we tested for the influence of transgenerational effects on the Insecticide × Temperature interaction in the crop pest moth Spodoptera littoralis. Specifically, we analysed reaction norms among experimental clutches based on a split-plot design crossing the factors temperature, insecticide and clutch. The study was performed on 2280 larvae reared at four temperatures (23, 25, 27 and 29 °C), and their response to the insecticide deltamethrin (three concentrations and a control group) was tested. Temperature had a global influence with effects on larval survival, duration of development, pupal body mass, and significant reaction norms of the clutches for temperature variations of only 2 °C. In addition to the expected effect of deltamethrin on mortality, the insecticide slightly delayed the development of S. littoralis, and the effects on mortality and development differed among the clutches. Projection models integrating all the observed responses illustrated the additive effects of deltamethrin and temperature on the population multiplication rate. Variation in the response of the clutches showed that transgenerational effects influenced the impact of insecticide and temperature. Although no evidence indicated that the Insecticide × Temperature interaction depended on transgenerational effects, the studies on the dependence of the Insecticide × Temperature interaction on other factors continue to be crucial to confidently predict the combined effects of insecticides and climate warming.

International audience | Climate warming is expected to impact the response of species to insecticides. Recent studies show that this interaction between insecticides and temperature can depend on other factors. Here, we tested for the influence of transgenerational effects on the Insecticide x Temperature interaction in the crop pest moth Spodoptera littoralis. Specifically, we analysed reaction norms among experimental clutches based on a split-plot design crossing the factors temperature, insecticide and clutch. The study was performed on 2280 larvae reared at four temperatures (23, 25, 27 and 29°C), and their response to the insecticide deltamethrin (three concentrations and a control group) was tested. Temperature had a global influence with effects on larval survival, duration of development, pupal body mass, and significant reaction norms of the clutches for temperature variations of only 2°C. In addition to the expected effect of deltamethrin on mortality, the insecticide slightly delayed the development of S. littoralis, and the effects on mortality and development differed among the clutches. Projection models integrating all the observed responses illustrated the additive effects of deltamethrin and temperature on the population multiplication rate. Variation in the response of the clutches showed that transgenerational effects influenced the impact of insecticide and temperature. Although no evidence indicated that the Insecticide x Temperature interaction depended on transgenerational effects, the studies on the dependence of the Insecticide x Temperature interaction on other factors continue to be crucial to confidently predict the combined effects of insecticides and climate warming.

Sustained cultivation of Bacillus thuringiensis (Bt) transgenic crops requires stable transgene expression under variable abiotic conditions. We studied the interactions of Bt toxin production and chronic ozone exposure in Bt cry1Ac-transgenic oilseed rape and found that the insect resistance trait is robust under ozone elevations. Bt Cry1Ac concentrations were higher in the leaves of Bt oilseed rape grown under elevated ozone compared to control treatment, measured either per leaf fresh weight or per total soluble protein of leaves. The mean relative growth rate of a Bt target herbivore, Plutella xylostella L. larvae was negative on Bt plants in all ozone treatments. On the non-transgenic plants, larval feeding damage was reduced under elevated ozone. Our results indicate the need for monitoring fluctuations in Bt toxin concentrations to reveal the potential of ozone exposure for altering dosing of Bt proteins to target and non-target herbivores in field environments experiencing increasing ozone pollution. Elevated atmospheric ozone can induce fluctuations in insecticidal protein concentrations in transgenic plants.

v | 2009 | ok | puj

Insecticides have long been used as the main method in limiting agricultural pests, but their widespread use has resulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects of sublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larvae.

Insecticides have long been used as the main method in limiting agricultural pests, but their widespread use hasresulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects ofsublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larvae.

International audience | Insecticides have long been used as the main method in limiting agricultural pests, but their widespread use has resulted in environmental pollution, development of resistances, and biodiversity reduction. The effects of insecticides at low residual doses on both the targeted crop pest species and beneficial insects have become a major concern. In particular, these low doses can induce unexpected positive (hormetic) effects on pest insects, such as surges in population growth exceeding what would have been observed without pesticide application. Methomyl and chlorpyrifos are two insecticides commonly used to control the population levels of the cotton leafworm Spodoptera littoralis, a major pest moth. The aim of the present study was to examine the effects of sublethal doses of these two pesticides, known to present a residual activity and persistence in the environment, on the moth physiology. Using a metabolomic approach, we showed that sublethal doses of methomyl and chlorpyrifos have a systemic effect on the treated insects. We also demonstrated a behavioral disruption of S. littoralis larvae exposed to sublethal doses of methomyl, whereas no effects were observed for the same doses of chlorpyrifos. Interestingly, we highlighted that sublethal doses of both pesticides did not induce a change in acetylcholinesterase activity in head of exposed larvae