Whiteflies Interfere with Stressed Plants' Chemical Cry for Help

Plants under herbivore attack are able to protect themselves by emitting chemical signals recognized by the herbivore's natural enemies. For instance, bean plants under spider mite (Tetranychus urticae) attack produce compounds to attract predatory mites (Phytoseiulus persimilis). These mites are specialized predator of spider mites, acting as a type of "bodyguard" for the plant. However, little is known about how plants respond to infestation by multiple herbivores, particularly if these belong to different feeding guilds.

Researchers at Wageningen University in the Netherlands describe in a paper published by PNAS how whiteflies (Bemisia tabaci) interfere with the chemical signal production of bean plants under attack by spider mites. The scientists looked at the production of the compound beta-omicene. They found that the compound is produced in much lower quantities if the plant is not only attacked by spider mites, but also by whiteflies. The production of the odor decreases because of a lower expression rate of the plant gene that codes for a crucial enzyme in the production chain. When the researchers added ocimene to the odor of plants which were attacked by both species, the attraction of predatory mites was restored. The researchers observed that spider mites produce more offspring on a plant under attack by whiteflies.

The results of this study are significant for integrated crop protection in which a combination of methods can be used to fight various pests infesting a crop. Once it becomes clear which insects weaken plant defense systems and which strengthen them, more focused research on environmentally-safe pest control will be possible, according to the researchers.

The original article is available at http://www.wageningenuniversity.nl/UK/newsagenda/news/White091125.htm Download the PNAS paper at http://dx.doi.org/10.1073/pnas.0907890106