Persistence and nimaticidal efficacy of phorate in soil and residues in fruit of Citrus reticulata (L.)

Appliitian of phorate @ 0.5 and 1.0 kg a.i./ha in the basin area of Citrus reticulata (L.) resulted in the persistence of its residues in soil beyond 60 days as determined by quantitation of residues in gas chromatographic analysis. In the top 15 cm soil, the nematicide dissipated in a linear fashion and showed a half-life of 8.9 and 11.9 days at the low and high rates of application, respectively. Leaching of phorate residues (0.11–0.40μg/g) beyond 15cm depth was observed within 10 days following flooding of the orchard in the first week of applicatian. However, the residues were retained mainly in the top 15 cm soil layer. Basin treatment even at a low rate of 0.5 kg a.i./ha was quite effective against citrus nematode, Tylenchulus semipenetrans as well as other ectoparasitic nematodes in the soil. The residues in peal, juice and rind of fruit as analysed from 3 days onwards, varied between non-detectable to trace level only.