Natural predators have key role in killing resistant aphids

Natural predators could have a vital role in controlling insecticide-resistant peach potato aphids, with new research suggesting they are more susceptible to attack than those without the mutation.

Pyrethroid resistance has been increasingly seen over the years since it was first discovered in arable pests in 1997 and its overuse may be to blame.

Sacha White, senior research entomologist at Adas, pointed to the growing use of pyrethroids over the last 40 years, at the recent Association of Independent Crop Consultants conference near Towcester.

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“In the late 1980s, pyrethroids accounted for one-quarter of total pesticide usage.”

It jumped to 80% in the 1990s and by 2012, more than 90% of insecticides applied were pyrethroids, he added.

Resistance pressure

This has created huge resistance pressure, exacerbated by few new insecticides becoming available to farmers.

One key pest showing resistance is the peach potato aphid, which carries many costly diseases including turnip yellows virus and beet yellows virus.

Routine sampling in England by Rothamsted shows most carry both super knockdown resistance to pyrethroids and Mace resistance to pirimicarb.

While this makes control difficult, he suggested that there was a glimmer of hope because of their differing responses to the alarm pheromone.

Aphids produce alarm pheromones to warn others when they come under attack.

In addition, there have been suggestions that these pheromones could be used to repel aphids off crops.

However, Dr White’s research found that resistant peach potato aphids are less responsive.

“So could they be more sensitive to parasitoids?”

Parasitoids are insects where the larvae live inside the pest and eventually kill it.

One example is the parasitic wasp and Dr White found in a trial that there was an increased kill of peach potato aphids. He believes it also applies to other predators.

“This suggests you need to keep your friends, as beneficials can help.”