Apathetic aphids - which become accustomed to ignoring genetically engineered chemical alarms in plants and alarms sent by fellow aphids - become easy prey for ladybugs. That's good news for farmers, according to researchers at the Boyce Thompson Institute for Plant Research and Cornell University.
The study, 'Alarm pheromone habituation in Myzus persicae has fitness consequences and causes extensive gene expression changes,' was authored by Georg Jander, associate scientist at the Boyce Thompson Institute (BTI) located on the Cornell campus, and Robert Raguso, Cornell professor of neurobiology and behaviour. Co-authors also include 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.
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, said Jander: 'When we put ladybugs into the mix, the ones that are habituated to the alarm pheromone get eaten more.' 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.