In a recent post on genetically modified wheat crops producing the aphid alarm pheromone (E)-beta-farnesene, I suggested some doubts related to results published in literature. I concluded my post writing: “This does not imply that this trial is not interesting at all, since there is scattered evidence in the literature suggesting that alarm pheromone emission might serve as an indirect defense by attracting aphid predators and it will be very interesting to see what will happen to aphid predation”.
A further doubt emerges now from a recent paper published by Ameixa & Kindlmann in the Journal of Applied Entomology where one of the most surprising results is that (E)-beta-farnesene did not elicit any strong response from the Aphidius colemani aphid parasitoids. Furthermore, it seems that in order to influence the behaviour of A. colamani, the (E)-beta-farnesene must be in a combination with other plant volatiles. This result support a previous study by Mumm and Hilker (2005) who has shown that a high concentration of (E)-beta-farnesene became repellent to the egg parasitoid Chrysonotomyia ruforum.
To achieve a complete understanding of the parasitoid behaviour in this system, further observations and ﬁeld experiments should be made in the future and probably it is too early for suggesting that genetically modified wheat crop will be the final solution for aphid damages. We have a lot of work to do since, as recently Carl Zimmer stated, in biology being the godawful mess that it is, it seems that different factors work together, rather than in isolation.
Mumm R, Hilker M (2005) The signiﬁcance of background odour for an egg parasitoid to detect plants with host eggs. Chem. Senses, 30, 337-343
Ameixa O, Kindlmann P (2011) Effect of synthetic and plant-extracted aphid pheromones on the behaviour of Aphidius colemani Journal of Applied Entomology, in press.
Image: Bio-bee biological systems