Jasmonic acid induces the production of gerbera volatiles that attract thebiological control agent Phytoseiulus persimilis

Jasmonic acid (JA) is a plant hormone that is involved in the induction of plant defence in response to herbivore attack. We studied the effect of exp osure of gerbera leaves to JA on indirect plant defence, i.e. attraction of natural enemies of herbivores. Treatment of gerbera leaves with JA or feed ing damage by the herbivorous spider mite Tetranychus urticae, both induced the production of a complex odour blend that attracts the predatory mite P hytoseiulus persimilis. This phytoseiid predator is a very effective biolog ical control agent of the spider mite T. urticae. Comparison of headspace c omposition of gerbera leaves exposed to either JA or T. urticae revealed a large degree of resemblance, but some quantitative and qualitative differen ces were recorded. The major chemical group in both treatments is formed by the terpenoids which quantitatively comprised up to 80% of the total odour blend. These terpenoids included (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-be ta-ocimene and linalool that are known to attract P. persimilis. Aldehydes, alcohols, esters and ketones, together with nitrogenous compounds formed t he remaining constituents of the odour blend. The induction of predator att ractants in plants by JA may be applied in biological control programs, whi ch is discussed in this paper.