Uptake of the insecticide, fenitrothion, by fruit bodies of shiitake (Lentinus edodes) from treated bed logs

Abstract

The uptake of fenitrothion by fruit bodies of shiitake, Lentinus edodes (BERK.) SING., from treated bed logs was investigated. Chemical treatment of bed logs colonized with shiitake was performed by immersion in a diluted emulsion of the chemical or by spraying. The fruit bodies and the surface barks of bed logs were sampled at intervals during about one year for residual analyses of fenitrothion. It was detected in the fruit bodies, indicating that it was transferred to them from the bed logs by vegetative hyphae. The amounts of fenitrothion in the fruit body samples varied and were correlated with the chemical treatment methods. No difference of fenitrothion concentrations was detected between pilei and stems of the fruit bodies. The residues of fenitrothion in fruit bodies growing on bed logs treated by the spraying method were less than the tolerance level set by the Ministry of Health and Welfare, Japan for fenitrothion residues in food. An abundance of chemical was detected in the barks of bed logs, but it decreased gradually after chemical treatment.