An assessment was made of the fumigant toxicity of 20 constituents from catnip oil and another additional five previously identified compounds of the oils and control efficacy of three experimental spray formulations containing catnip oil (1, 0.5 and 0.1% sprays) to females from B- and neonicotinoid-resistant Q-biotypes of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Spathulenol (LC50, 0.39 μg/cm3) and thymol (0.45 μg/cm3) were the most toxic compounds, followed by carvacrol, α-terpineol, nerol, linalool, menthol and eugenol toward Q-biotype females (0.85–1.24 μg/cm3). The toxicity of these compounds was virtually identical toward both biotype females, indicating that the terpenoids and the insecticides (neonicotinoids and dichlorvos) do not share a common mode of action or elicit cross-resistance. The 0.5% spray of oil formulation resulted in > 80% mortality toward both biotype females. Global efforts to reduce the level of toxic synthetic insecticides in the agricultural environment justify further studies on catnip oil-derived materials as potential contact-action fumigants for the control of B. tabaci populations.

The insecticidal activity of 120 plant essential oils and control efficacy of six experimental spray formulations (SF) containing the oils (SF-0.25, 0.5, 1, 2.5, 5 and 10% sprays) against both nymph and adult of citrus flatid planthopper, Metcalfa pruinosa, was examined using a direct contact application. Reponses varied according to dose (1000 mg litre-1 and 500 mg litre-1). Based on 24 h exposure in leaf dipping assay at 1000 mg litre-1 strong mortality was observed in more than 19 essential oils among 130 was screened. At 500 mg litre-1 very strong mortality (100%) was observed in cinnamon technical, cinnamon green leaf, cinnamon #500, cassia tree, citronella java and penny royal followed by origanum, thyme white, grape fruit, savory, fennel sweet, aniseed and cinnamon bark (93.3- 80%) showed considerable moratality against nymphs of M. pruinosa. The moderate mortality was found in thyme red, tagette, calamus, lemoneucalptus and geranium (73.3-60%). The other oil has low or very low mortality against M. pruinosa. The oil applied as SF-10% sprays provided 100% mortality against adult M. pruinosa. In particular cinnamon technical showed very strong (>SF-0.5= 100%) effect followed by cinnamon #500 (>SF-2.5=100%), cinnamon green leaf (>SF-2.5=100%) and penny royal (>SF-2.5=100%) respectively. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active essential oils as potential larvicides for the control of M. pruinosa populations as direct spray with contact action.

An assessment was made of the toxicity of basil, Ocimum basilicum, essential oil, 11 basil oil constituents, seven structurally related compounds and another 22 previously known basil oil constituents and the control efficacy of four experimental spray formulations containing the oil (1, 2, 3 and 4% sprays) to adult American house dust mites, Dermatophagoides farinae. Results were compared with those of two conventional acaricides benzyl benzoate and N,N-diethyl-3- methylbenzamide (deet). The active principles were determined to be citral, α -terpineol and linalool. Citral (24 h LC50, 1.13 μg/cm2) and menthol (1.69 μg/cm2) were the most toxic compounds, followed by methyl eugenol (5.78 μg/cm2). The toxicity of these compounds was more toxic than that of benzylbenzoate(LC50, 8.41 μg/cm2) and deet (37.67 μg/cm2). These compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapour action. Basil applied as 3 and 4% experimental sprays provided 97 and 100% mortality against the mites respectively, whereas permethrin (cis:trans, 25:75) 2.5 g/l spray treatment resulted in 17% mortality. Reasonable mite control in indoor environments can be achieved by spray formulations containing the basil oil (3 and 4% sprays) as potential contact-action fumigants.

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.