Key to Figures / Image Credits

Figure 1. The photograph of Mentha spicata was shared by Doug (shyzaboy@Flickr) of Troutville, VA via the Botany Photo of the Day Flickr Pool). Thank you for the contribution, Doug!

Figure 2. The illustration of Cinnamomum zeylanicum is from Köhler's Medizinal-Pflanzen (Band I), via Wikimedia Commons.

Figure 3. The photograph of the larva of Trichoplusia ni is courtesy of Alton N. Sparks, Jr., University of Georgia, Bugwood.org, Wikimedia Commons.

A belated ending to the Celebrate Research Week @ UBC series, due to a little bit of miscommunication. Here is the last entry for the series this year, organized by Claire. Claire introduces today's UBC researcher:

Yasmin Akhtar is a research associate in the insect toxicology lab with Dr. Murray B. Isman and lectures in the Faculty of Land and Food Systems. She works with botanical insecticides and antifeedants.

Yasmin writes: Culinary herbs including mint (Mentha spicata) (Figure 1) and spices such as cinnamon (Cinnamomum zeylanicum) (Figure 2) are used as insect control agents. Figure 3 shows a cabbage looper (Trichoplusia ni) larva, considered to be an agricultural pest.

Plants are sources of a bewildering array of natural products including terpenoids, phenolic and alkaloids, likely exceeding 100,000 chemical structures. Many of these chemicals provide defensive functions for the plants protecting them against herbivores and pathogens. Based on their defensive chemistry complex, vascular plants have been considered a valuable resource of natural insecticides, insect growth regulators, and behaviour modifying agents. Behaviour modifying agents may influence the feeding and oviposition (egg-laying) behavior of insects and may also serve as repellents.

The main focus of research in our lab is the development of botanical insecticides and antifeedants. We are exploring the potential use of natural pesticides based on plant essential oils. Some of these oils and their constituent chemicals are widely used as flavoring agents in foods and beverages and are even exempt from pesticide registration in the United States. Plant essential oils meet the criteria of reduced risk pesticides (Isman, 2008).

Plants producing essential oils that have been exploited for insect control include a number of herbs, most notably from the mint family (Lamiaceae), such as garden thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), and various species of mint (Mentha spp.). Other important sources are tropical trees, notably clove (Syzygium aromaticum) and cinnamon (Cinnamomum zeylanicum). Many of the essential oils have shown insecticidal, repellent, feeding deterrent (Jiang et al., 2010) and antimicrobial effects against a number of pests. Some of these oils or their constituents serve as active ingredients in commercially available insecticides, herbicides or repellents. Thymol, for example, a key essential oil constituent of garden thyme, is registered in Europe for the control of two important parasitic mites of the honey bee (Apis mellifera). Eugenol, a primary constituent of clove oil, is an active ingredient of a broad-spectrum insecticide (EcoPCO® D) sold by EcoSMART Technologies. Essential oil of rosemary is the active ingredient in two botanical insecticides currently used in the United States (HexacideTM and EcotrolTM).

We are also looking at the development of non-toxic crop protection chemicals that mimic naturally occurring bioactive odorants and tastants, and that are relatively easily prepared from commodity chemicals (Akhtar et al., 2010). We also look at the role of experience on the feeding behavior of larvae and oviposition choices of the subsequent moths with emphasis on habituation and dishabituation as well as learning and memory in insects (Akhtar et al., 2009). Cabbage looper (Trichoplusia ni), green peach aphids (Myzus persicae), confused flour beetles (Tribolium confusum), rust red flour beetle (Tribolium castaneum), and fruit flies (Drosophila melanogaster) are the major research insects. We also work with two-spotted spider mite (Tetranychus urticae). Bioassays are conducted to determine the feeding and oviposition deterrent effects of an essential oil. Feeding deterrent substances deter feeding in insects. Similarly, oviposition deterrent substances deter insects from laying eggs on the plants. Since insect damage to plants may result from feeding/oviposition or from transmission of pathogens during feeding, the chemicals that reduce pest injury by rendering plants unattractive or unpalatable may serve as potential substitutes for conventional insecticides.

References:

Akhtar, Y., Yu, Y., Isman, M.B., and Plettner, E. (2010). Dialkoxybenzene and dialkoxyallylbenzene feeding and oviposition deterrents against the cabbage looper, Trichoplusia ni: potential insect behavior control agents. Journal of Agricultural and Food Chemistry. 58: 4983-4991. DOI: 10.1021/jf9045123

Jiang, Z.L., Akhtar, Y., Zhang, X., Bradbury, R. and Isman, M.B. (2010). Insecticidal and feeding deterrent activities of essential oils in the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae). Journal of Applied Entomology. DOI: 10.1111/j.1439-0418.2010.01587.x

Akhtar, Y., Shikano, I., and Isman, M.B. (2009). Topical application of a plant extract to different life stages of Trichoplusia ni fails to influence feeding or oviposition behaviour. Entomologia experimentalis et applicata. 132: 275-282.

Isman, M.B. (2008). Botanical insecticides: for richer for poorer. Pest Management Science 64:8-11.