| Resumo: |
Increasing horticultural production under protected cultivation requires more detailed studies about the occurence of pesticide residues, due to the special and peculiar environment under controlled conditions, in which some pests, that are of little concern in the field, become important. The insecticide acephate and its methamidophos metabolite residues were evaluated in greenhouse-grown tomatoes and compared to an open-field tomato crop. The treatments: (a) check; (b) one application of 75 g a.i. acephate.100 L-1 water; (c) one application of 150 g a.i.100 L-1 water; (d) four applications of 75 g a.i.100 L-1 water were evaluated. Fruit, leaf and soil samples were taken at (-1), zero, 1, 3, 7, 14, 21 days after the last or only application. The quantitative determinations were done by gas chromatography, using flame-photometric detector. The acephate and methamidophos residues in fruits harvested in the greenhouse and in the field were always below their respective maximum residue levels (MRL) during the whole sampling period. The metabolism of acephate into methamidophos was very low in fruits, especially important in leaves, but not well characterized in soil. Acephate residues were higher in the greenhouse than in the field, especially in leaves and soil, showing stability and persistence up to the 7-day-sampling after application.
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