Every year, approximately 700,000 people die from complications associated with etiologic disease agents transmitted by mosquitoes. While insecticide-based vector control strategies are important for the management of mosquito-borne diseases, insecticide-resistance and other logistical hurdles may lower the efficacy of this approach, especially in developing countries. Repellent technologies represent another fundamental aspect of preventing mosquito-borne disease transmission. Among these technologies, spatial repellents are promising alternatives to the currently utilized contact repellents and may significantly aid in the prevention of mosquito-borne disease if properly incorporated into integrated pest management approaches. As their deployment would not rely on prohibitively expensive or impractical novel accessory technologies and resources, they have potential utility in developing countries where the burden of mosquito-borne disease is most prevalent. This review aims to describe the history of various repellent technologies, highlight the potential of repellent technologies in preventing the spread of mosquito-borne disease, and discuss currently known mechanisms that confer resistance to current contact and spatial repellents, which may lead to the failures of these repellents. In the subsequent section, current and future research projects aimed at exploring long-lasting non-pyrethroid spatial repellent molecules along with new paradigms and rationale for their development will be discussed.

There is an urgent need to explore and utilize naturally occurring products for combating harmful agricultural and public health pests. Secondary metabolites in the leaves of the Tree of Heaven, Ailanthus altissima L. have been reported to be herbicidal and insecticidal. The mode of action, however, of the active compounds in A. altissima are not understood. In this paper, we report the chemical characteristics of the herbicidal and insecticidal components in this tree, and will discuss the effect of light on the bioactivity of the active components. Extracts from the fresh leaves of A. altissima showed a strong plant germination/growth inhibitory effect in laboratory bioassays against alfalfa (Medicago sativa). The effect was dose-dependent. The growth inhibitory components were in the methylene chloride soluble fraction of the extract. The effect was greater in the light than in the dark. Other fractions had plant growth enhancing effect at lower concentrations. The extract was slightly insecticidal against yellow fever mosquito larvae (Aedes aegypti). The extract or its semi-purified fractions of A. altissima were strong plant growth inhibitors, therefore good candidates as potential environmentally safe and effective agricultural pest management agents. The finding that light affects the activity will be useful in the application of such natural products.

Mosquito-borne diseases account for the deaths of approximately 700,000 people annually throughout the world, with many more succumbing to the debilitating side effects associated with these etiologic disease agents. This is exacerbated in many countries where the lack of mosquito control and resources to prevent and treat mosquito-borne disease coincide. As populations of mosquito species grow more resistant to currently utilized control chemistries, the need for new and effective chemical means for vector control is more important than ever. Previous work revealed that plant essential oils enhance the toxicity of permethrin against multiple mosquito species that are of particular importance to public health. In this study, we screened permethrin and deltamethrin in combination with plant essential oils against a pyrethroid-susceptible and a pyrethroid-resistant strain of both Aedes aegypti and Anopheles gambiae. A number of plant essential oils significantly enhanced the toxicity of pyrethroids equal to or better than piperonyl butoxide, a commonly used synthetic synergist, in all strains tested. Significant synergism of pyrethroids was also observed for specific combinations of plant essential oils and pyrethroids. Moreover, plant essential oils significantly inhibited both cytochrome P450 and glutathione S-transferase activities, suggesting that the inhibition of detoxification contributes to the enhancement or synergism of plant essential oils for pyrethroids. This study highlights the potential of using diverse plant oils as insecticide additives to augment the efficacy of insecticidal formulations.

Veterinary antibiotics enter the environment through the application of organic fertilizers to cropland. In this study, the aerobic degradation of tylosin, a widely used antibiotic in the production of livestock and poultry, was conducted in water and in soil in an effort to further investigate its environmental fate. Tylosin is a macrolide antibiotic, which consists of four factors (A, B, C, D). Water and soil were sampled at selected times and analyzed for tylosin and its degradation products by high-performance liquid chromatography (HPLC), with product identification confirmed by HPLC-mass spectrometry. Tylosin A is degraded with a half-life of 200 d in the light in water, and the total loss of tylosin A in the dark is 6% of the initial spiked amount during the experimental period. Tylosin C and D are relatively stable except in ultrapure water in the light. Slight increases of tylosin B after two months and formation of two photoreaction isomers of tylosin A were observed under exposure to light. However, tylosin probably would degrade faster if the experimental containers did not prevent ultraviolet transmission. In soil, tylosin A has a dissipation half-life of 7 d, and tylosin D is slightly more stable, with a dissipation half-life of 8 d in unsterilized and sterilized soil. Sorption and abiotic degradation are the major factors influencing the loss of tylosin in the environment, and no biotic degradation was observed at the test concentration either in pond water or in an agronomic soil, as determined by comparing dissipation profiles in sterilized and unsterilized conditions.