Fungicide residues in pears, apples and grapes after post harvest treatments by thermonebulization.

In the context of trials conducted in cold store, in order to investigate efficacy of fruit protection applying agrochemicals, the fate during the storage of two active ingredients (a.i.): pyrimethanil and imazalil, have been studied. The experimental trials were done on eight varieties of apples and pears and two of grapes. Only field use of named pesticides was already authorised on fruits and maximum residue limits (MRL) fixed. In the present biennial experimentation (apples and pears in the first year; grapes in the second one). Two fungicides formulations were applied and treatments have been executed by thermonebulization technique. The storage cell, had a volume of 110 m3 filled up with the fruits until 80% of its capacity. Each fruit variety constituted one thesis of 4 replicates. For each trial, only one treatment was performed at the beginning of conservation period (72 days for pears and apples, and 57 days for grapes). In order to estimate fungicides persistence, residues determinations have been carried out. From results obtained especially on grape, not homogenous residues distribution on treated commodities was observed. For all theses, residue level has not evidenced statistically significant decrement as function of time, behaviour not as observed in field tests. The following average values of residues have been determined: in apples and pears, 0.7 mg/kg of imazalil much lower than 5 mg/kg (RML fixed for field use), and 1.2 mg/kg of pyrimethanil little higher than 1 mg/kg (RML fixed for field use); in grapes 0.5 mg/kg pyrimethanil much lower than 3 mg/kg (RML fixed for field use).