Abstract Fruit-disc samples were assayed microbiologically to determine streptomycin residues on the skin and in the flesh of peach, plum, apricot, apple, and pear fruits taken from trees which had received four to five sprays of ‘Agrimycin 17’ containing 100 ppm streptomycin. The sampling and assay method employed allows quantitative measurements to be made quickly on large numbers of samples. It was found that streptomycin deposits of the order 0.01 μg/0.5 cm2 of skin and 0.05 μg/0.5 cm2 of fruit flesh could be detected. All detectable streptomycin on sprayed fruit was confined to the skin. Streptomycin deposits were greater and their removal was slower on the hairy-skinned fruits such as peaches and ‘Newcastle’ apricots than on apples, pears, and plums. Deposits on apples and peaches decreased with time after spraying, both with and without rain or artificial washing. Washing removed some of the streptomycin, but other factors appear to be involved in its removal or decay on fruit surfaces. On all frui...
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