Toxicity of Petroleum Oils to Larvae and Eggs of Some Cotton Insects and Persistence of These Oils on Cotton Foliage12

Abstract

Two aromatic oils applied topically had LD50 values of 4.0 mg/g with larvae of the bollworm, Heliothis zea (Boddic), and 0.015 mg/g with the beet armyworm, Spodoptera exigua (Hubner). Low volume sprays of paraflinic and isoparaffinic oils applied in the laboratory to eggs of the tobacco budworm, H. virescens (F.), reduced hatch 70 and 86%, respectively, and a naphthenic oil used as a conventional spray on cotton plants in field cages reduced the rate of larval weight gain 25% in the cabbage looper, Trichoplusia ni (Hubner), and 66% in the tobacco budworm. Residues of paraffinic, naphthenic, and isoparaffinic oils on leaves of cotton plants in a field cage showed that 86–100% were lost 6 days after each of 2 applications. Also, only 39% of the methyl parathion diluted in acetone on cotton leaves was lost after 24 hours; much greater percentages of methyl parathion diluted in 4 other solvents (3 oils) were lost.