International audience | 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-diffusionreaction equations, driven by abiotic and biotic factors. The target species is the grain aphid, Sitobion avenae F., considering both its winged and apterousmorphs. 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.

It has been 14 years since the world's largest Ulva bloom appeared in the Yellow Sea, China in 2007. Although it is clear that the Ulva bloom originates from the culture system of Porphyra yezoensis (Nori) in the southern Yellow Sea, how to control it is still little understood. Since overwintering banks played a crucial role in the development of spring population of green algae on the cultivation ropes, here, a promising method was presented to prevent the development of Ulva bloom by the inactivation of the overwintering banks of green algae on the P. yezoensis cultivation ropes during February and early March. Chlorine dioxide, an environment-friendly disinfectant was used as algaecide with dosage of no lower than 40 mg/L at the contact time of 1 min. The overwintering green algae gradually disappeared within two weeks after the treatment. Furthermore, the growth of spring population of green algae on the cultivation ropes was effectively inhibited for at least eight weeks, which contribute to prevent the formation of floating populations during cultivation facilities collection. It was expected that the present method, if to be applied in the P. yezoensis cultivation areas in southern Yellow Sea, may mitigate the magnitude of the Ulva blooms in the Yellow Sea at a lower cost.

The environmental characteristics of Ahe deep lagoon (Tuamotu Archipelago, French Polynesia) were studied over 3years with the aim of explaining the spatial and temporal variability of the natural food available for pearl oysters with a special focus on phytoplankton biomass and global photosynthesis/respiration ratio of the lagoon. Chlorophyll averaged 0.34±0.01μgL⁻¹ and our findings did not confirm increased phytoplankton biomass in deep lagoonal waters. Phytoplankton production appears to be limited firstly by nitrogen and respiratory processes overpass photosynthetic processes at least in the north-eastern edge of the atoll. Grazing by pearl oysters in culture seems to decrease the POC concentration but not the phytoplankton biomass. Oysters graze mainly on non chlorophyllian particles.

Since the invasion of the fall armyworm moth (Spodoptera frugiperda) in China in January 2019, damage to maize crops has gradually intensified, and chemical control has become the main control measure. This study aimed to examine methods of effective pest control while monitoring the environmental impact of pesticide use. The effectiveness of S. frugiperda pest control by foliar spraying and root irrigation of maize plants with acephate was determined, and the absorption, distribution, and dissipation of acephate and methamidophos by maize were studied. Field trials showed that acephate treatment at 6000 g a.i. ha⁻¹ was the most effective for controlling S. frugiperda. Acephate and methamidophos were absorbed from the roots, transported upward, and concentrated in the leaves, particularly new leaves. The terminal residues of acephate and methamidophos in maize grains were below detectable levels at 60 days after treatment. The results demonstrate that acephate treatment via root irrigation can more effectively control the infestation of S. frugiperda in maize than acephate treatment via foliar spraying. The translocation and distribution of acephate and methamidophos by root irrigation were more uniform, and the holding efficiency was higher than those in foliar spraying, suggesting an extended period of control efficacy. This pest control method could be utilized to reduce pesticide residues while safely and efficiently controlling S. frugiperda infestation.

Metal-containing plant incineration ash (MPIA), which was the by-product for metal extraction from soil by phytoextraction process, contains various kinds of heavy metal that have post potential risk to the environment. This study investigated the leaching efficiency and metal redistribution of MPIA using organic acid as leaching agents. The MPIA before and after leaching was characterized using the toxicity characteristic leaching procedure (TCPL) test, X-ray diffraction, scanning electronic microscopy, and Fourier transform infrared spectroscopy. The results showed that all tested organic acids resulted in the dissolution of metals, especially 1 mol L⁻¹ citric acid leaching achieved for the dissolution efficiency of 84% Mn, 87.01% Cd, 66.97% Zn, and 55.83% Pb. During leaching progress, the synergetic of chelation and acid soluble action accelerated the metal release and redistribution, and the dissolution of Mn, Zn, Pb, and Cd fit best to the shrinking core model of chemical control. Meanwhile, the leaching residue reached the regulatory standard. Thus, organic acid leaching may be a feasible strategy for detoxification of MPIA.

The diamondback moth, Plutella xylostella, is recognized as a widely distributed destructive insect pest of Brassica worldwide. The management of this pest is a serious issue, and an estimated annual cost of its management has reached approximately US$4 billion. Despite the fact that chemicals are a serious threat to the environment, lots of chemicals are applied for controlling various insect pests especially P. xylostella. An overreliance on chemical control has not only led to the evolution of resistance to insecticides and to a reduction of natural enemies but also has polluted various components of water, air, and soil ecosystem. In the present scenario, there is a need to implement an environmentally friendly integrated pest management (IPM) approach with new management tactics (microbial control, biological control, cultural control, mating disruption, insecticide rotation strategies, and plant resistance) for an alternative to chemical control. The IPM approach is not only economically beneficial but also reduces the environmental and health risks. The present review synthesizes published information on the insecticide resistance against P. xylostella and emphasizes on adopting an alternative environmentally friendly IPM approach for controlling P. xylostella in China.

Currently, the poor water quality in Taihu Lake is a major problem in China, so pollution control in the upstream areas has become a government priority. In Jiangsu Province, pollution emissions around the western areas of Taihu Lake, including Changzhou Municipality and Yixing City, need to be highly restricted, and calculating the water environmental capacity is important if pollution is to be reduced. In this study, 19 control units in these areas were established, and a 0-D mathematical model was used to calculate the water environmental capacity. For three important control units with important cross sections, a 1-D model was established to redress the results. Finally, the total maximum monthly loads of each control unit were obtained using temporal allocation principles. The results suggested that (1) the total pollution control of chemical oxygen demand was 58,894.2 tonnes per annum (t a⁻¹), with ammonia nitrogen, total nitrogen, and total phosphorus amounting to 3,808, 6,054.6, and 386.6 t a⁻¹, respectively; (2) water environmental capacity per unit water area in the ambient control units was smaller than that in the middle control units; and (3) the largest water environmental capacity was in June, and the smallest capacity was in December. The study provides important information for local governments, which will enable them to implement pollution control strategies that will improve the water quality in Taihu Lake.