Wasp ‘bodyguards’ could be used as biological pesticide © Getty Images

Wasp ‘bodyguards’ could be used as biological pesticide

Older varieties of maize plant can send out a chemical signal to recruit parasitic wasps when 'stemborer' wasps lay their eggs on its leaves.

The natural ability of some maize plants to resist insect attack could be harnessed as a biological pesticide, according to new research led by Keele University.

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Pests can cause devastating losses to crops, but some maize plants will send out a chemical signal when a ‘stemborer’ moth has laid its eggs on the plant, in order to recruit parasitic wasps that lay their eggs in the moth caterpillars.

To find out more about the genetics behind the defence mechanism, Keele University’s Prof Toby Bruce, in collaboration with the International Centre of Insect Physiology and Ecology, and International Crops Research Institute for the Semi-Arid Tropics in Kenya, investigated the genetics of 146 types of maize plants.

The plants included traditional, farmer-selected varieties of maize (known as ‘landraces’), as well as inbred lines and commercial hybrids.

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The plants were exposed to stemborer eggs, in order to test the chemicals released and to measure how attractive they were to the wasps. They found that the wasp-attraction trait was more common in the landrace varieties, and they also pinpointed the region on the genetic code connected with the response.

“Farmers urgently need alternative approaches for managing crop pests as use of pesticides is increasingly restricted by changes in legislation and evolution of pesticide resistance,” said Bruce.

“Here we show how biological control of pests can be enhanced in crops. We have identified regions of the maize genome associated with a ‘cry for help’ trait that allows crops to call in parasitic wasp bodyguards to defend them when they are attacked by pests.”

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As crop plants have been selectively bred and domesticated, some have become more vulnerable to insect pests. There is increasing pressure on farmers to reduce their use of chemical pesticides, and this new genetic analysis could help in the development of crop varieties that can naturally resist pests. So while they might be annoying at your picnic, wasps are not all bad.

What’s the best way to get wasps to go away?

Wasps are attracted to white, bright blue and yellow, but can’t see red, so plan your wardrobe accordingly.

Their vision is also optimised to look for the sudden, sharp movements of insects, so wildly flailing as you try to swat a wasp will just make it more determined.

Killing a wasp also releases pheromones that will attract other wasps nearby. Instead, calmly trap the wasp under a glass, so it can’t return to the nest and tell the others where to find your food.

A 2012 study tested the wasp-repelling properties of different essential oils and found that a mix of clove, geranium and lemongrass oil was the most effective, so try a dab behind each ear.

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