Phorate Residues in Tomato Fruit and Foliage1

Abstract

Phorate and oxidative metabolite residues in tomato fruit and foliage were determined by the cholinesterase inhibition procedure. In 10% granular form, up to 5 pounds active photate was applied in bands in soil furrows on either side of the row at transplanting and later dates. Fruit samples contained less than 0.10 p.p.m. phorate residues regardless of whether sampled in the immature green, mature green or pink ripe stage of development. Subsequent ill vitro oxidation of fruit resulted ill slightly greater cholinesterase ill only the immature green tomato fruit. Cholinesterase inhibiting residues in the tomato foliage range from less than 0.10 p.p.m. to 4.0 p.p.m. depending on prior treatments and sampling dates. Residues in the tomato foliage following a number of treatments appeared to approach a maximum at two periods of plant development. These peak residue periods in the foliage were usually correlated with preceding periods of relatively high field temperatures and ample rainfall. Control of serpentine leaf miners (Liriomyza brassicae (Riley)) was effective for at least 2 months after transplanting following application of 3 or 5 pounds of active phorate per acre to the soil.