Science & Environment

Red alert for oilseed rape as colour change curbs pests

oilseed rape
Image caption When coloured red, oilseed rape is not as attractive to pollen beetles

The blazing yellow colour of oilseed rape that dominates the UK countryside in the spring could one day become a sea of red, say scientists.

Researchers at Rothamsted found that changing the colour of the crop's petals from yellow to red can be an environmentally friendly method of controlling pollen beetles.

This insect is becoming increasingly resistant to chemical pesticides.

The study has been published in the journal Arthropod-Plant Interactions.

Although traditionally used to give soils a break between crops of wheat or barley, oilseed rape has boomed in the UK in recent years as demand has soared for the oil made from the plant.

But the bright yellow petals and sweet scent of the plant have attracted growing numbers of pests, especially pollen beetles. Chemical sprays have long been used to control the insect but resistance has been rising.

Red effect

Now scientists at Rothamsted say they have a new strategy for containing the beetle. In this experiment the researchers used food colouring to change the colour of the leaves of a variety with white petals.

"We grew oilseed rape in pots, washed off the soil and put the plants into buckets of water," lead author Dr Sam Cook told BBC News.

"And we basically poured food colouring into the water. This was taken up by the roots of the plant and was manifested in the colour of the petals."

Image caption Oilseed rape is widely grown across the UK as demand has soared for biofuels

The team coloured the petals yellow, blue and red. In the laboratory and in field trials over two years they found these made a big difference to the pollen beetles.

"Red was significantly less preferred than the blue, and then yellow and white were pretty much the same," said Dr Cook.

"It's a bright red - almost a blood red really," she said.

The researchers showed that the beetles are more attracted to objects that are highly reflective of ultraviolet light. This knowledge could open up new strategies for managing the pest say the research team.

"We could breed red coloured plants. The anthocynanin gene is responsible for purple and red colouration - this gene is present in the oil seed rape family so we could breed that into oilseed rape to give a red colouration to the green parts and the petals," said Dr Cook.

Colour trap

One alternative being examined by several companies is to have no petals at all. Another approach could be to mix and match colours that the insects find attractive and repellent.

Image caption An artists impression of how the UK countryside might look in the future with yellow plants acting as insect traps on the outer edges of fields

By planting yellow varieties around the edge of a field with red cultivars in the middle you would design a trap, that would keep the pests from the oil producing crop.

"It's a push pull strategy - the main crop is pushing the insect away and the trap crop is pulling it into this area where it can be controlled more easily," said Dr Cook.

She says that the fields of the UK could one day become a multicoloured mosaic.

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