| dc.description.abstract | The topical toxicity of 12 essential oil components (carvacrol, 1,8-cineole, trans-cinnamaldehyde, citronellic acid, eugenol, geraniol, S-(-)-limonene, (-)-linalool,
(-)-menthone, (+)-α-pinene, (-)-β-pinene, and thymol) to adult male, adult female, gravid female, and large, medium, and small nymphs of the German cockroach, Blattella germanica (L.) was determined. Thymol was the most toxic essential oil component to adult males, gravid females, and medium nymphs with LD50 values of 0.07, 0.12, and 0.06 mg/cockroach, respectively. Trans-cinnamaldehyde was the most toxic essential oil component to adult females, large nymphs, and small nymphs with LD50 values of 0.19, 0.12, and 0.04 mg/cockroach, respectively. (+)-α-Pinene was the least toxic essential oil
component to all stages of the German cockroach. S-(-)-Limonene had the least effect on ootheca hatch, with 35.21 (mean) nymphs hatching per ootheca. (-)-Menthone had the
greatest effect on ootheca hatch with 20.89 nymphs hatching per ootheca. The numbers of nymphs hatching from each ootheca generally declined as dose increased.
The fumigant toxicity of the 12 essential oil components to all life stages of the German cockroach, Blattella germanica (L.) was determined. 1,8-Cineole was the most toxic essential oil component to adult males and females, gravid females, and large nymphs with LC50 values of 6.84, 8.43, 5.31, and 11.44 mg/L air, respectively. (-)-Menthone and carvacrol were the most toxic essential oil components to medium and small nymphs with LC50 values of 8.96 and 3.63 mg/L air, respectively. Citronellic acid was the least toxic essential oil component to all stages of the German cockroach. Citronellic acid had the least effect on ootheca hatch (100% hatch). (-)-Menthone had the greatest effect on ootheca hatch (73% hatch). The percentage hatched oothecae decreased linearly with increasing concentration.
The repellency of the 12 essential oil components to adult male German cockroaches, Blattella germanica (L.) was determined using Ebeling choice boxes and the harborage-choice method. Repellency ranged from a high of 45% for citronellic acid to 6% for S-(-)-limonene in the Ebeling choice box. Repellency was negatively correlated with fumigant toxicity. Repellency ranged from 76% for carvacrol to 43% for 1,8-cineole using the harborage-choice method. Repellency was negatively correlated with vapor pressure. ANOVA showed that there was a significant effect of day on repellency for both the Ebeling choice boxes and the harborage-choice method. The Ebeling choice box is the superior method for determining the repellency of essential oils to the German cockroach because it is a better approximation of normal cockroach habitat, and it is designed to measure the percentage of repelled cockroaches, rather than repellency persistence. | en |
