This study examines the food-chain transfer of Zn from two plant species, Urtica dioica (stinging nettle) and Acer pseudoplatanus (sycamore maple), into their corresponding aphid species, Microlophium carnosum and Drepanosiphum platanoidis. The plants were grown in a hydroponic system using solutions with increasing concentrations of Zn from 0.02 to 41.9 mg Zn/l. Above-ground tissue concentrations in U. dioica and M. carnosum increased with increasing Zn exposure (p < 0.001). Zn concentrations in A. pseudoplatanus also increased with solution concentration from the control to the 9.8 mg Zn/l solution, above which concentrations remained constant. Zn concentrations in both D. platanoidis and the phloem tissue of A. pseudoplatanus were not affected by the Zn concentration in the watering solution. It appears that A. pseudoplatanus was able to limit Zn transport in the phloem, resulting in constant Zn exposure to the aphids. Zn concentrations in D. platanoidis were around three times those in M. carnosum. Concentrations of Zn in two aphid species are dependant on species and exposure.

The transfer of Cd and Zn from soils amended with sewage sludge was followed through a food chain consisting of wheat, aphids and the predator Coccinella septempunctata. Multiple regression models were generated to predict the concentrations of Cd and Zn in C. septempunctata. No significant model could be generated for Cd, indicting that the concentration of this metal was maintained within relatively narrow limits. A model predicting 64% of the variability in the Zn concentration of C. septempunctata was generated from of the concentration of Zn in the diet, time and rate of Zn consumption. The results suggest that decreasing the rate of food consumption is an effective mechanism to prevent the accumulation of Zn and that the availability of Zn in the aphid prey increased with the concentration in the aphids. The results emphasise the importance of using ecologically relevant food chains and exposure pathways during ecotoxicological studies. Arthropod predators can regulate trace metal body burden through physiological and behavioural mechanisms.

Aphids are important insect pests and are considered a major threat to various crops. In the laboratory experiment, our objective is to assess the toxicity level of some newer synthetic insecticides, viz. Imidacloprid, Flonicamid, and Spirotetramat against different species of aphids viz. maize leaf aphids (Rhopalosiphum maidis), green peach aphids (Myzus persicae), and mustard aphids (Liphaphis erysimi). The leaf dip bioassay was conducted to evaluate the LC50 and LT50 values. Among these novel molecules, Spirotetramat was the most toxic insecticide against R. maidis and M. persicae, with median lethal concentrations (LC50) of 0.68 and 3.99 ppm, and Flonicamid was the most toxic against L. erysimi with an LC50 value of 5.79 ppm. The median lethal concentrations for the Imidacloprid, Flonicamid, and Spirotetramat are different for each species of aphids. The LT50 values of the given insecticides revealed that the Imidacloprid has the potential for giving effective control of R. maidis, M. persicae, and L. erysimi species, as evidenced by the shorter time required for 50% mortality with LT50 values of 44.53, 49.19 and 44.90 hrs respectively with median lethal concentrations of 4.20, 5.14 and 10.86 ppm. The results indicated variations in toxicity among these different chemicals against different insect species.

We expose here a detailed spatially explicit model of aphid population dynamics at the scale of a whole country (Metropolitan France). It is based on convection–diffusion-reaction equations, driven by abiotic and biotic factors. The target species is the grain aphid, Sitobion avenae F., considering both its winged and apterous morphs. In this preliminary work, simulations for year 2004 (an outbreak case) produced realistic aphid densities, and showed that both spatial and temporal S. avenae population dynamics can be represented as an irregular wave of population peak densities from southwest to northeast of the country, driven by gradients or differences in temperature, wheat phenology, and wheat surfaces. This wave pattern fits well to our knowledge of S. avenae phenology. The effects of three insecticide spray regimes were simulated in five different sites and showed that insecticide sprays were ineffective in terms of yield increase after wheat flowering. After suitable validation, which will require some further years of observations, the model will be used to forecast aphid densities in real time at any date or growth stage of the crop anywhere in the country. It will be the backbone of a decision support system, forecasting yield losses at the level of a field. The model intends then to complete the punctual forecasting provided by older models by a comprehensive spatial view on a large area and leads to the diminution of insecticide sprayings in wheat crops.