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.

The toxicity of red pine needle hydrodistillate, its constituents, and 12 structurally related compounds to third instar larvae of insecticide-susceptible Aedes aegypti and wild Aedes albopictus was examined using a direct-contact bioassay. Results were compared with those of the currently used larvicides fenthion and temephos. The red pine needle hydrodistillate constituents were identified by GC-MS and co-elution of authenticated samples following co-injection. Based on 24 h LC50 values, 3-carene (8.60–9.33 mg/L), limonene (10.34–10.77 mg/L), and thymol (10.65–11.45 mg/L) were the most toxic constituents. The moderate toxicity was produced by (1S)-(–)-α-pinene, p-cymene, geranyl acetate, myrcene, and β -caryophyllene (LC50, 27.62–38.01 and 28.61–39.52 mg/L). Overall, these compounds were less effective than either fenthion (LC50, 0.012–0.022 mg/L) or temephos (LC50, 0.010–0.015 mg/L). In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, red pine needle hydrodistillate and the compounds described merit further study as potential larvicides for the control of mosquito populations.