That’s good news for farmers, according to researchers at the Boyce Thompson Institute for Plant Research and Cornell University, including Georg Jander, associate scientist at the Boyce Thompson Institute (BTI) located on the Cornell campus; Robert Raguso, Cornell professor of neurobiology and behavior; Martin de Vos, a former BTI post-doctoral researcher; Wing Yin Cheng, a former undergraduate researcher in Jander’s lab; and Holly Summers, a graduate student in Raguso’s lab.

Their study – “Alarm pheromone habituation in Myzus persicae has fitness consequences and causes extensive gene expression changes,” – was published recently in the Proceedings of the National Academy of Sciences of August 3, 2010.

Under normal circumstances, when a ladybug captures and bites into an aphid, the victim releases an alarm pheromone called beta-farnesene, prompting nearby aphids to walk away or drop off the plant. When aphids are raised on plants genetically engineered to emit beta-farnesene, they become accustomed to the chemical and no longer respond to it – even when a predator is present – making them easy prey.

Aphids reared continuously on genetically engineered Arabidopsis thaliana plants that produced beta-farnesene became habituated to the pheromone within three generations and no longer responded to the compound. In the absence of predators, the habituated aphids produce more progeny, likely because they expended less energy on running away and focus more on feeding compared to normal aphids.

However, “when we put ladybugs into the mix, the ones that are habituated to the alarm pheromone get eaten more,” said Jander. Anxious aphids – those actually responding to pheromone alarms – had a higher survival rate in the presence of predators.

Genetically engineered crop plants or those that naturally produce the aphid alarm pheromone, for instance some potato varieties, could be used to increase the effectiveness of aphid predators as part of future crop protection strategies.