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Experts Find Bacteria That Help Pests Change Colour

Scientists in Japan and France have identified a bacterium which appears to turn red plant lice green, enabling them to evade predators and thrive on crops.

The discovery has important implications for pest control as these lice, or aphids, are among the most destructive insects in temperate regions, sucking on the sap of cultivated plants.

“These bacteria makes aphids invisible to predators like the ladybird and beetle,” said the lead author of the study, Tsutomu Tsuchida of the Molecular Entomology Laboratory at RIKEN (Advanced Science Institute) in Saitama prefecture in Japan.

“If we can eliminate these bacteria, the aphids will stay red and they will be easily recognized by predators. This discovery is very useful for agricultural purposes,” he said by telephone.

The study was published Nov. 19 inSciencemagazine.

There are 4,400 species of aphids – small, soft-bodied insects with long, slender mouths that pierce stems, leaves, and other tender plant parts to suck out fluids. They may be green, yellow, brown, red or black, depending on the species and the plants they feed on.

Almost every plant has one or more species which feed on it.

Well adapted and difficult to eliminate, aphids cause 30 per cent of losses in wheat crops in France and 50 per cent in barley.

Tsuchida and col leagues were studying aphids feeding on peas in France when they found green aphids producing red offspring that later turned green as they matured.

Using antibiotics, they eliminated a string of other bacteria from the aphids and singled out a new bacterium, Rickettsiella, which appeared to turn red aphids green.

Tsuchida said this effect of colour change may be tranferrable to baby aphids through the ovaries – which explains why the offspring appear red at first but turn green.

“Their phenotypic effect, i.e. changing body colour, is also transmitted to the next generations,” he said.

Tsuchida’s team has already begun work to try to thwart the effects of the bacteria on aphids but this will take time.

“We are trying to eliminate these bacteria by using many antibiotics, but we can’t do it. Now we are examining the mechanism by which the bacteria affects later generations of aphids and how it changes their body colour,” he said.

“Once we understand the mechanism, we can try to (stop or reverse) the colour change.”

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