Reentry problems involving the use of dialifor on grapes in the San Joaquin Valley of California

An illness episode characterized by cholinesterase depression and cholinergic symptoms was noted among 118 field workers harvesting grapes treated with dialifor and phosalone compounds in a vineyard near Madera, Calif. Dialifor had been applied at the rate of 1.0 lb/acre in 30 gal of water from 15-40 days earlier using a kinkelder air blast sprayer. Workers were exposed to levels of dislodgeable residues as high as 0.7 mg/sq cm; however, most residue levels were in the range of 0.11-0.45 mg/sq cm. Dialifor residues on the foliage in 36 other grape vineyards in the San Joaquin Valley were determined at the time of harvest and were shown to be 0.13 mg/sq cm. None of the field workers in these vineyards showed abnormally high blood cholinesterase values. The investigation indicated that, with initial dislodgeable dialifor residue levels as high as 2.3 mg/sq cm, a period of at least 65 days is required before a possibly safe levels of less than 0.06 mg/sq cm is reached. Phosalone residues in the vineyard were not responsible for the illness of the field workers.