ABSTRACT
In agroecosystems with papaya, the neonicotinoid insecticide thiamethoxam is used by producers for its high effectiveness in controlling pests in soil and plant. In Mexico, to date, there are no regulations that control the use and management of thiamethoxam, however, internationally the EPA (Environmental Protection Agency), EFSA (European Food Safety Authority) and FAO (United Nations Organization for Food) have established maximum tolerance and residuality limits. In view of the above, this study was conducted with the purpose of determining the presence and residuality of the insecticide thiamethoxam in agroecosystems with papaya, and thus know the relationship with its use and management. The chosen study area is located in the municipality of Cotaxtla, Veracruz, Mexico. Three stages were raised, in the first one a survey of agricultural producers was carried out to know what pesticides they handle in papaya crops and also the structure of the agroecosystem. Subsequently, using the snowball technique a survey was conducted on the management of thiamethoxam in the agroecosystem. The second stage of the investigation consisted in determining the concentrations of thiamethoxam in soil matrices, irrigation water, plant and fruit. The treatments corresponded: T1 = Watermelon cultivation, T2 = Land preparation, T3 = Papaya transplant, T4 = Papaya fruit production, using HPLC-UV equipment for its determination. The third stage consisted of carrying out a risk projection of the management of thiamethoxam, evaluating four doses of thiamethoxam in papaya cultivation for this purpose and also estimating the bioconcentration of thiamethoxam in soil, irrigation water, plant and papaya fruit. The agroecosystem is structured in 27% by papaya producers, another 45% of them associate the cultivation of papaya with watermelon and the remaining 28% cultivates other fruits. Of the papaya-related producers, 6% manage pest control using neonicotinoid insecticides. The results denoted residual thiamethoxam in soil, irrigation water, papaya plant and fruit, in the different phenological phases of papaya and watermelon cultivation. Concentration levels exceeded the tolerance and residual limits of EPA, EFSA and FAO. The contamination by thiamethoxam management corresponds to a bioaccumulation of 17.63 kg/ha in soil, 45 kg/ha in irrigation water of the crop, 20 g/ha in papaya plant and 89.1 g/ha in whole papaya fruit. The scenario shown in the thiamethoxam risk projection on the Cotaxtla and Soyolapa river, as it does not present a control in the management that avoids the presence and residuality of thiamethoxam in the papaya agroecosystem, could affect aquatic organisms and public health.
Keywords: Neonicotinoids, tropical fruit trees, pollution