Bioassays of Rosmarinus officinalis L. essential oil and blends of its major constituents were conducted using host-specific strains of the two-spotted spider mite, Tetranychus urticae Koch, on bean and tomato plants. Two constituents tested individually against a bean host strain and five constituents tested individually against a tomato host strain accounted for most of the toxicity of the natural oil. Other constituents were relatively inactive when tested individually. Toxicity of blends of selected constituents indicated a synergistic effect among the active and inactive constituents, with the presence of all constituents necessary to equal the toxicity of the natural oil.

Contact toxicity of essential oils of Litsea pungens Hemsl. and L. cubeba (Lour.) Pers. (Lauraceae) and of blends of their major constituents was assessed against third-instar Trichoplusia ni larvae via topical application. Both oils showed moderate activity against T. ni larvae with LD(50) values of 87.1 and 112.5 microg/larva, respectively. 1,8-Cineole from the essential oil of L. pungens and gamma-terpinene from the oil of L. cubeba accounted for much of the toxicity of the oils to T. ni larvae. The toxicity of blends of selected constituents indicated a synergistic effect among putatively active and inactive constituents, with the presence of all constituents necessary for full toxicity of the natural oils. The results show that essential oils of L. pungens and L. cubeba and some of their constituents have potential for development as botanical insecticides.

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Rosemary [Rosmarinus officinalis L. (Lamiaceae)] essential oil has insecticidal properties and is the active ingredient in a number of commercial insecticides. Like other plant essential oils, the chemical composition of rosemary oil can vary based on genotype, geography, climate, and method of preparation. This study explored the relationship between chemical composition and insecticidal activity of 10 commercial samples of rosemary oil, based on laboratory bioassays with two agricultural pests, the armyworm Pseudaletia unipuncta Haworth (Noctuidae) and the cabbage looper Trichoplusia ni Hübner (Noctuidae). Nine major terpenoid constituents of rosemary oil were quantified in the samples by gas chromatography-mass spectrometry (GC-MS). The major constituents were 1,8-cineole, α-pinene, β-pinene, and camphor; on average 1,8-cineole made up 52% of the oil by weight. Bioassayed individually, camphor was the most toxic compound to the armyworm (LD 50 =189.4 µg larva −1) whereas µ-terpineol was the most toxic to the looper (LD 50 =128.5 µg larva −1). LD 50 values for the ten rosemary oils ranged from 167.1 to 372.1 µg larva −1 in the armyworm and from 58.9 to 335.9 µg larva −1 in the looper. Correlation analysis comparing rosemary oil toxicity to chemical composition revealed slight but significant correlation for d-limonene and α-terpineol in bioassays with the looper but no correlations between constituents and toxicity with the armyworm. An "artificial" rosemary * Dedicated to Professor John Thor Arnason of the University of Ottawa, Department of Biology, on the occasion of his sixteith birthday.

Extracts from three species of the plant family Piperaceae, Piper nigrum [L.], Piper guineense [Schum & Thonn, and Piper tuberculatum [Jacq.], were tested for efficacy against insects from five orders. All three species contain isobutyl amides, plant secondary compounds that act as neurotoxins in insects. These materials are considered safe to mammals because Piper spp. were used for centuries for spice and medicinal purposes. When 24-h P. nigrum LC50 values were compared between common insect pests from eastern Canada and the northeastern United States, the most sensitive species in order of increasing lethal concentration were eastern tent caterpillar, Malacosoma americanum (F.) < European pine sawfly larvae, Neodiprion sertifer (Geoffroy) < spindle ermine moth larvae, Yponomeuta cagnagella [Hübner] < viburnum leaf beetle larvae, Pyrrhalta viburni [Paykull] < stripped cucumber beetle adults, Acalymma vittatum (F.) < Colorado potato beetle adults, Leptinotarsa decemlineata (Say) < Japanese beetle adults, Popillia japonica [Newman] < hairy chinch bug, Blissus leucopterus hirtis [Montandon]. The life stage tested was the point at which each species causes the greatest amount of damage to the host plant and the point at which most gardeners would likely choose to treat with a conventional synthetic insecticide. Greenhouse trials revealed that the pepper formulations also had a repellent activity, thus protecting plant leaves from 1) herbivory (lily leaf beetle, Lilioceris lilii [Scopoli], adults and larvae and stripped cucumber beetle adults) and 2) oviposition [European corn borer, Ostrinia nubilalis (Hübner)]. Combinations with other botanical extracts were additive at best in toxicity and repellent trials. Nontarget toxicity to beneficial invertebrates is a possibility because the P. nigrum LC50 for beneficial ladybird beetles was 0.2%. P. nigrum extracts can provide a reasonable level of control against lepidopteran and European pine sawfly larvae and also will work as a short-term repellent and feeding deterrent. It is recommended that the use of Piper extracts be restricted to small-scale spot treatments in residential areas where insect pest outbreaks have occurred.