Wintergreen = Biocontrol Aromatherapy

WHEN ENTOMOLOGISTS hip to chemical ecology speak of HIPPOs, they mean HERBIVORE INDUCED PLANT PROTECTION ODORS, not the massive hippopotamus native to riverine Africa. At Washington State University (WSU), David James and his entomological colleagues have spent the last several years testing fragrant wintergreen oil, a common HIPPO produced by distressed plants, as a means to boost biological control of crop pests by natural enemies.

The same fragrant wintergreen oil (high in methyl salicylate) used in mints and mouthwashes can be formulated into slow-release dispensers to attract beneficial insects into crops in greater numbers earlier in the season than would otherwise be the case. The dispensers minimize environmental and worker health impacts and crop damage (phytotoxicity). Also, the dispensers can last 3-4 months, providing extended periods of natural enemy attraction. Sprays evaporate more quickly, potentially meaning more applications. Nevertheless, spray technologies are still very popular and 2% wintergreen oil in canola oil is being test sprayed worldwide in crops ranging from hops and cotton to soybeans, strawberries and sweet corn.

In their earliest hop yard and grape vineyard field tests, James and his coworkers found that wintergreen oil attracted significantly higher numbers of pest natural enemies like predatory green lacewings, minute pirate bugs (Orius spp.), spider mite-eating lady beetles (Stethorus spp.), and aphid-eating syrphid flies. By getting higher numbers of natural enemies into the fields earlier than might otherwise have been the case, pests like spider mites were kept under biological control all season long. Leafhopper numbers were also lower, leading James to suspect that parasitic wasp species attacking this pest were also boosted by wintergreen oil.

This is the basis for commercial products such as PredaLure, sold by Rincon-Vitova Insectaries and others to maximize natural enemies providing biological pest control. Plants are virtual chatterboxes of chemical communication, and wintergreen oil and methyl salicylate are just the tip of the iceberg in terms of natural compounds awaiting field testing. Farnesene, caryophyllene and the male-produced lacewing aggregation pheromone iridodial are among the other green lacewing attractants attracting research attention.

When attacked by insects, spider mites, and pathogens (e.g. viruses, bacteria, fungi) or under environmental stress (e.g. chilling, drought, salinity), plants can ooze chemical exudates from their roots into the soil and waft a variety of communication chemicals into the wind. Thereby neutralizing pathogenic soil microbes, luring in pest-eating natural enemies and tipping off downwind neighbors in the plant community to ramp up their immune response in preparation for impending pest attacks.

We have only scratched the surface of what exists and what is possible to develop for biological insect control.

9 Responses to Wintergreen = Biocontrol Aromatherapy

  1. Tnelson says:

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  2. Your site was extremely interesting, especially since I was searching for thoughts on this subject last Thursday.

  3. Alia says:

    It looks like MeSA can signal fungi, too! I ran across this article and it made me think of your post:

    Hountondji FCC, Hanna R, Sabelis MW. 2006. Does methyl salicylate, a component of herbivore-induced plant odour, promote sporulation of the mite-pathogenic fungus Neozygites tanajoae? EXPERIMENTAL AND APPLIED ACAROLOGY, 39(1):63-74.

    Abstract: Blends of volatile chemicals emanating from cassava leaves infested by the cassava green mite were found to promote conidiation of Neozygites tanajoae, an entomopathogenic fungus specific to this mite. Methyl salicylate (MeSA) is one compound frequently present in blends of herbivore-induced plant volatiles (HIPV) as well as that of mite-infested cassava. Here, we investigated the effect of methyl salicylate in its pure form on the production of pre-infective spores (conidia), and the germination of these spores into infective spores (capilliconidia), by a Brazilian isolate and a Beninese isolate of N. tanajoae. Mummified mites previously infected by the fungal isolates were screened under optimal abiotic conditions for sporulation inside tightly closed boxes with or without methyl salicylate diffusing from a capillary tube. Production of conidia was consistently higher (37%) when the Beninese isolate was exposed to MeSA than when not exposed to it (305.5 +/- 52.62 and 223.2 +/- 38.13 conidia per mummy with and without MeSA, respectively). MeSA, however, did not promote conidia production by the Brazilian isolate (387.4 +/- 44.74 and 415.8 +/- 57.95 conidia per mummy with and without MeSA, respectively). Germination of the conidia into capilliconidia was not affected by MeSA for either isolate (0.2%, 252.6 +/- 31.80 vs. 253.0 +/- 36.65 for the Beninese isolate and 4.2%, 268.5 +/- 37.90 vs. 280.2 +/- 29.43 for the Brazilian isolate). The effects of MeSA on the production of conidia were similar to those obtained under exposure to the complete blends of HIPV for the case of the Beninese isolate, but dissimilar (no promoting effect of MeSA) for the case of the Brazilian isolate. This shows that MeSA, being one compound out of many HIPV, can be a factor promoting sporulation of N. tanajoae, but it may not be the only factor as its effect varies with the fungal isolate under study.

  4. Jan Meneley says:

    We are the U.S. supplier for PredaLure, the controlled release dispenser of wintergreen. Many university publications on PredaLure efficacy. Sprays do have to be repeated about every 7-10 days because of volatility.

    We also supply various insect pheromone lures and traps.

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