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Apathetic aphids become easier prey for ladybugs

August 11, 2010  By Fruit & Vegetable


August 11, 2010 –
Apathetic aphids – which become accustomed to ignoring genetically engineered
chemical alarms in plants and alarms sent by fellow aphids – become easy prey
for ladybugs.



August 11, 2010 –
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, 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.


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