Twelve Lamiaceae plant essential oils (EOs) and their components were evaluated for their fumigant and contact toxicities. Inhibition of AChE by the major components of active EOs was also assessed. Strong fumigant toxicity was observed from EOs of Mentha piperita and Perilla frutescens. Menthone and menthol, and perilla aldehyde were identified as major components of the above two EOs, respectively. The LC50 (mg/L) values of M. piperita, P. frutescens, menthone, menthol and perilla aldehyde were 3.87, 2.44, 5.76, 1.88, and 0.99 against male, and 4.10, 3.31, 5.13, 1.94, and 1.15 against female, respectively. Strong contact toxicity was observed from the EOs of Satureja montana and Thymus zygis. Thymol and carvacrol were major components of these two EOs. The LD50 (μg/fly) values for contact toxicity of S. montana, T. zygis, thymol and carvacrol were 2.95, 2.93, 1.63, and 1.30 for male, and 4.59, 5.09, 2.68, and 2.60 for female, respectively. Among the five major components, perilla aldehyde showed most active inhibition activity against AChE of both sexes of SWD.

Essential oils from 22 plant species were tested for their insecticidal activities against spotted wing drosophila (SWD), Drosophila suzukii Matsumura, using fumigation and contact bioassay. Responses varied with the essential oils, their constituents and concentrations. Strong fumigation activities were observed from the essential oils of wintergreen (Gaultheria fragrantissima), croton (Croton anisatum) and star anise (Illicium verum). Strong contact activities were observed in the essential oils of oriental sweetgum (Liquidambar orientalis), cassia (Cinnamomum cassia), damask rose (Rosa damascena) and sandalwood (Santalum album). The compositions of these selected essential oils were identified using gas chromatographymass spectrophotometer. The compounds identified were tested individually for their insecticidal activities against SWD. Responses varied by doses for each compound. The results showed that natural materials are as effective as synthetic pesticides.

Fumigant and contact toxicities of 11 Myrtaceae plant essential oils and their constituents against adult male and female Blattella germanica were evaluated. Of 11 Myrtaceae plant essential oils, Eucalyptus polybractea, E. smithii, E. radiata, E. dives, E. globulus, and Melaleuca uncinata, showed 100% fumigant toxicity against adult male German cockroaches at a concentration of 7.5 mg/liter air concentration. In contact toxicity tests, E. polybractea, E. smithii, E. radiata, E. dives, E. globulus, M. dissitiflora, and M. uncinata produced strong insecticidal activity against adult male and female German cockroaches. Of the essential oil constituents, terpinolene, α-terpinene, and terpinen-4-ol demonstrated strong fumigant toxicity against adult male and female B. germanica. Eugenol, isoeugenol, methyl eugenol, and terpinen-4-ol showed strong contact toxicity against adult male B. germanica. The toxicity of the constituent blends identified from M. dissitiflora essential oils indicated that terpinen-4-ol were major contributor to the fumigant activity or contact toxicity of the artificial blend. Only isoeugenol exhibited inhibition activity against male acetylcholinesterase. IC50values of isoeugenol were 0.22 mg/mL against male acetylcholinesterase.

An assessment was made of the toxicity of hiba, Thujopsis dolabrata var. hondai, oil and 24 oil constituents and control efficacy of four experimental spray formulations containing the oil (0.5. 1, 2, and 3% sprays) to adult American house dust mite (AHDM), Dermatophagoides farinae, and copra mite (CM), Tyrophagus putrescentiae. Results were compared with those of three conventional acaricides benzyl benzoate, N,N-diethyl-3-methylbenzamide (deet), and permethrin. Based on 24 h LC50 values, (–)-thujopsene was the most toxic constituent against AHDM (9.82 μg/cm2) and CM (10.92 μg/cm2) and the toxicity of the compound was nearly identical to that of benzyl benzoate (9.33 and 10.14 μg/cm2). High toxicity was also observed with (–)-(E)-pinocarveol, carvacrol, (+)-terpinen-4-ol, β-thujaplicin, cedrol, α-terpineol, (+)-ledene, thymol, and 2,4-di-tert-butylphenol against both mite species (LC50, 11.92–19.19 and 12.49–22.97 μg/cm2). These constituents were more toxic than deet (LC50, 35.53 and 38.42 μg/cm2). Hiba applied as 2 and 3% sprays provided >95% mortality against both mite species, whereas permethrin (cis:trans, 25:75) 2.5 g/L spray treatment resulted in ca 11% mortality. Global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments justify further studies on hiba oil preparations containing the constituents described as potential contact-action fumigants or lead molecules for the control of mite populations.

The toxicity of red pine needle hydrodistillate (RPN-HD), 19 RPN-HD constituents and 12 structurally related compounds and control efficacy of four experimental spray formulations containing RPN-HD (0.5. 1, 2 and 3% sprays) to adult Dermatophagoides farinae was evaluated. RPN-HD (24 h LC50,68.33 μg cm–2) was toxic. Menthol was the most toxic compound (12.69 μg cm–2) and the toxicity of this compound and benzyl benzoate did not differ significantly from each other. High toxicity was also produced by α-terpineol, bornyl acetate, geranyl acetate, thymol, linalyl acetate, terpinyl acetate, citral, linalool and camphor (18.79–36.51 μg cm–2). These compounds were more toxic than either deet or dibutyl phthalate. In vapour-phase mortality tests, these compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapour action. RPN-HD 3% experimental spray provided 95% mortality against adult D. farinae, whereas permethrin (cis:trans,25:75)2.5gL–1 spray treatment resulted in 0% mortality. In the light of global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments, RPN-HD and the compounds described merit further study as potential biocides for the control of Dermatophagoides populations as fumigants with contact action.