Effects of cuticular waxes on permeation of fungicides azoxystrobin and chlorothalonil into apples

Time-dependent permeation characteristics of two fungicides azoxystrobin and chlorothalonil into apples were investigated in the presence and absence of the cuticular waxes. Either apple samples which were subjected to wax-removing treatment or not (raw) were individually submerged in each dilution solution of the tested fungicides for a short time, and some of each submerged sample were then washed in running tap water. All apple samples were incubated under controlled conditions and collected sequentially after 1, 24, and 48h. The collected apple samples were divided into four tissue parts before fungicide residue analysis: peel, pulp-1, pulp-2, and pulp-3. Most residues of azoxystrobin (70.786.4%) in apples were present in the peel, and the residual extents in the pulps increased by removal of cuticular waxes. By washing treatment, 52.3-69.2% of azoxystrobin residues in raw apples were removed. Meanwhile, all chlorothalonil residues were determined in the peel of apples, and their concentrations slightly increased by wax removal. However, significant chlorothalonil residues (84.5-91.1%) were removed by washing the apple surface. Results in this study may be extensively utilized as basic data to understand characteristics of cuticular permeation and translocation of fungicides applied on fruit crops.