The protection of carrots against carrot fly (Psila rosae) with granular and emulsifiable concentrate formulations of chlorfenvinphos incorporated in gels used for drilling pre germinated seed in a sandy loam

Abstract

SUMMARYField experiments were done in a sandy loam in 1979 and 1980 to investigate the performance against carrot fly on carrots of e. c. and granular formulations of chlorfenvinphos incorporated in gels used for drilling pre‐germinated seed.With 9·4–66·7 mg a. i./m row, the two formulations performed similarly in a natural hydrocolloid and a mineral colloid gel. Thus the emergence of carrot seedlings 6–7 wk after drilling was similar on plots with untreated gel and those with insecticide‐treated gel and, about 6 months after drilling when > 90% of carrots grown without insecticide were damaged by carrot fly larvae, an approximately six‐fold increase in dose of both formulations increased the estimated larval mortality from about 70 to 95%. Mean concentrations of residues of total (Z + E) isomers of chlorfenvinphos in harvested carrots treated with 9·4–56·5 mg a. i./m row were<the proposed FAO/WHO tolerance for chlorfenvinphos (0·4 mg/kg). The initial rates of release of available chlorfenvinphos from a granular formulation immersed in the two types of gel differed markedly but, after 48‐h immersion, >50% of the insecticide had been released into both gels.