A new approach to enlisting beneficial insects in the war on mites, aphids, thrips and other

pests also may boost plant defences in other ways.

Researchers are showing that attractants placed in growers’ fields, orchards and vineyards

mimic defensive odours that plants release, drawing in greater numbers of hungry insect

predators. And some tests hint at a secondary pest-repelling effect.

Plants produce a variety of compounds known as herbivore-induced plant volatiles, or HIPVs,

in response to pest injury.

These chemicals in turn alert beneficial insects that prey is in the area.

Of them, methyl salicylate so far produces the best results, says David James, associate

professor of entomology at Washington State University’s Prosser research and Extension

centre.

Dispensers that emit methyl salicylate are available in both synthetic and organic forms from

InSense Pty. Ltd, of Cobram Australia.

PredaLure, the name under which the product is marketed, is being tested in crops ranging

from fruit, tomato, cabbage, broccoli, grapes, strawberries and corn.

Results show the influx of beneficial insects helps keep aphid, mite and leafhopper pest

populations below economic thresholds in test fields.

The compounds also seem to improve pest control with ripple effects.

“It’s a plant signal,” James says. “If one plant gives it off, adjacent plants recognize that pests

are nearby and do the same.”

Placing dispensers around crops early in the season jumpstarts that reaction and magnifies

the signal, pulling in defenders before pests arrive, he says. An “attract-and-reward” strategy

that also provides habitat for these incoming natural enemies can encourage them to stay

through the growing season.