Insecticidal activity of plant essential oils against Pediculus humanus capitis (Anoplura: Pediculidae)

The insecticidal activity of 54 plant essential oils against female Pediculus humanus capitis De Geer was examined using direct contact and fumigation methods, and compared with the lethal activity of delta-phenothrin and pyrethrum, two commonly used pediculicides. In a filter paper contact bioassay with female P. humanus capitis, the pediculicidal activity was more pronounced in eucalyptus, marjoram, pennyroyal, and rosemary oils than in delta-phenothrin and pyrethrum on the basis of LT50 values at 0.0625 mg/cm2. At 0.125 mg/cm2, pediculicidal activity of cade, cardamone ceylon, clove bud, myrtle, rosewood, and sage oils was comparable with that of the test insecticides. In fumigation tests with female P. humanus capitis at 0.25 mg/cm2, eucalyptus, marjoram, pennyroyal, and rosemary oils were more effective in closed containers than in open ones, indicating that the effect of these oils was largely a result of action in the vapor phase. Neither delta-phenothrin nor pyrethrum exhibited fumigant toxicity. The essential oils described herein merit further study as potential control agents for P. humanus capitis.