Behavior of acylanilide and dicarboximidic fungicide residues on greenhouse tomatoes

The residual behavior of four dicarboximidic and three acylanilidic fungicides was studied in greenhouse grown tomatoes. In different experiments tomatoes underwent single spraying and five sprayings with an interval of 21 days, at rates of application of 380 and 760 g/ha (acylanilides) and 1500 and 3000 g/ha (dicarboximides). The harvesting was carried out weekly. Residues recovered after repeated sprayings confirmed the well-known trend of the four dicarboximidic fungicides: toxically significant accumulation in fruits several days after recommended preharvest times. Among acylanilides, only furalaxyl and benalaxyl showed the accumulation of residues but always at concentrations lower than legal limits, even before the fixed preharvest times. The possible need is raised to revise preharvest times for both categories of fungicide. When tomatoes were single sprayed, the fungicide disappearance from fruits showed pseudo-first-order rate dependence only for dicarboximides; degradation products of the latter, found in a different matrix (wine), were not detected.