Wild Plants Call to Carnivores to Get Rid of Pests
Wild Plants Call to Carnivores to Get
Rid of Pests
While this strategy may work in
someone's backyard, it's not an option on a large farm. In an October 4 Trends in
Plant Science Opinion paper, agricultural researchers in Sweden and Mexico
argue that one way around the scalability problem is to bring back the odors
and nectars found in wild plants that attract pest-eating predators. This could
be done either through breeding programs or by using artificial devices.
"Wild plants commonly emit
natural odors when they are damaged that attract natural enemies of pest
insects--even as humans we smell it when our neighbour is mowing the lawn --
odors can carry very precise information," says co-author Martin Heil of
CINVESTAV-Irapuato in Mexico. "Agriculture has bred such defenses out of
crops, and since these odors have no negative effects on human consumers, we
want to replace what the plant would already be doing."
It's also not unusual for wild
plants to produce nectar on their leaves to feed carnivores. While leaf-eating
caterpillars or beetles are munching away on plant matter, predatory ants or
wasps have a sugary substance to drink and a well-stocked spot to lay their
eggs.
Heil and others theorize that the
reason these rather helpful traits no longer exist in crops is because plant
breeders and decision makers couldn't tell the difference between helpful
insects and pests. Only in the past 30 years has it been recognized that plants
use odors to communicate to one another and to other species. Such defenses
involve multiple genes, however, and it won't be easy to simply bring them
back.
One faster alternative would be
to plant crops alongside other species that both attract carnivores and repel
pests. The downside is that intercropping requires more work during harvesting
and its success rate isn't 100%. Another option is to create mechanical
dispensers that could release carnivore-calling odors and fungicidal nectar,
which is something Heil and his team are now developing and testing.
"New regulations and
changing consumer demands are gradually improving the prospects for more
sustainable agriculture," Heil says. "This provides a ready market if
we can give crops back their own immune system, either by breeding, genetic
engineering, or replacing the traits artificially."