Suckling, D. M. | Search bioRxiv

bioRxiv2016

First record of double-edged sword effect of caterpillar-induced plant volatiles in nature

Plants release volatiles in response to caterpillar feeding that attract natural enemies of the herbivores, a tri-trophic interaction which has been considered an indirect plant defence against herbivores. The caterpillar-induced plant volatiles have been reported to repel or attract conspecific adult herbivores. Apple seedlings infested with Pandemis pyrusana larvae uniquely release five compounds (benzyl alcohol, benzyl nitrile, phenylacetaldehyde, indole, and (E)-nerolidol). These compounds and other known caterpillar-induced plant volatiles were tested to investigate the response of both herbivores and natural enemies. In field tests, binary blends of benzyl nitrile and acetic acid or 2-phenylethanol and acetic acid attracted a large number of conspecific male and female adult moths. On the other hand, a ternary blend of benzyl nitrile, 2-phenylethanol and acetic acid attracted the largest numbers of the general predator, the common green lacewing, Chrysoperla carnea. This study provides the first record of caterpillar-induced plant volatile attraction to conspecific adult herbivores as well as predators under natural conditions.

ecology↗

bioRxiv2016

Use of phenylacetonitrile plus acetic acid to monitor Pandemis pyrusana (Lepidoptera: Tortricidae) in apple

A recent discovery have demonstrated that herbivore induced plant volatile compounds from apple tree infested with leafrollers were highly attractive to con-specific adult male and female leafrollers. However, this work has been conducted in New Zealand and Canada testing only low doses of kairomone. This study has been conducted in US to assess the attractiveness of higher doses of the six apple volatiles provisory identified in apple trees infested by tortricid larvaeto the leafroller, Pandemis pyrusana Kearfott. These volatiles included, {beta}-caryophyllene, germacrene D, benzyl alcohol, phenylacetonitrile, (E)-nerolidol, and indole. No volatiles were attractive to P. pyrusana when used alone. However, traps baited with phenylacetonitrile plus acetic acid caught both sexes of P. pyrusana. Traps baited with the other volatiles plus acetic acid caught zero to only incidental numbers of moths, [≤] 1.0. Adding phenylacetonitrile to traps baited with pear ester, ethyl (E,Z)-2,4-decadienoate plus acetic acid significantly reduced catches of codling moth, Cydia pomonella (L.). However, adding phenylacetonitrile to traps baited with codling moth sex pheromone, pear ester, and acetic acid did not similarly reduce moth catches of C. pomonella. Interestingly, traps baited with phenylacetonitrile plus acetic acid caught significantly more P. pyrusana than traps baited with a commercial sex pheromone lure. The evaporation rate of the acetic acid co-lure was an important factor affecting catches of P. pyrusana with phenylacetonitrile, and studies are needed to optimize the emission rates of both lure components. Further studies are warranted to develop phenylacetonitrile and possibly other aromatic plant volatiles as bisexual lures for the range of tortricid pests attacking horticultural crops.

ecology↗