Future use of plant signals in agricultural and industrial crops

Entomologists have begun to develop techniques involving vaccinations and applications of chemical elicitors to protect crops, applying what they know about the signals that mediate induced resistance. Apple and strawberry growers who tolerate some mites have realized reduced subsequent pest problems. Winegrape growers who have had chronically devastating populations of Pacific mites vaccinate their vines with less damaging Willamette mites and achieve smaller pest populations and improved yield. Vaccinations using live herbivores provide all the signals that plants use to induce resistance but are logistically difficult. Many chemicals have been identified as elicitors of induced resistance including one (benzothiadiazole) that is now marketed commercially for use against plant diseases. Exogenous application of jasmonic acid (JA) induces accumulation of many putatively defensive compounds and reduces herbivory in field situations. Ongoing experiments are evaluating the potential of exogenous JA applications in several crops. Recent evidence suggests that the pathways that plants use to protect against pathogens and against herbivores may be antagonistic, such that stimulating one depresses the other. The extent to which this trade-off may limit the ability of natural plants to defend themselves or agriculturists to limit plant parasites remains to be determined.