Crop pests in for surprise

Pest insects really love their food, say scientists. But new research is trying to understand why insect pests feed on some plants but not others.

CSIRO Entomology postdoctoral scientists Yasmin Cardoza, Sheena Cotter and Sam Migui are investigating what makes a pest stick to a particular diet.

"Herbivorous insects vary in the range of plants they will feed on. Some only feed on a single host plant species," says Dr Owain Edwards, head of CSIRO’s pest management - field crops project.

"But pest insects usually have a very wide host range," he says. "Very little is known about what factors determine what plants insects will feed on and what plants they won’t."

CSIRO Entomology and the Grains Research and Development Corporation (GRDC) hope that when these factors are identified, damaging pests can be prevented from feeding on key cropping species.

Under a new agreement between CSIRO and GRDC, Dr Migui, based in Montpellier, France, will be looking at genes in wheat which give some varieties resistance to the exotic pest, Russian wheat aphid. "This pest isn’t in Australia yet but is slowly spreading world wide," says Dr Migui.

"Its introduction would devastate Australian wheat crops," he says, "but I hope to identify resistance genes which can be introduced into popular Australian wheat varieties should the aphid ever be introduced to this country."

Dr Cardoza is studying the green peach aphid that feeds on plants in over 50 families.

"This feeding pattern is complicated by the fact that some populations within this species have a much more restricted host range with a few so specialised they feed on only one host," she says.

"Some experts consider these to be separate species," says Dr Cardoza. "I will be comparing the biology, behaviour, and genetics of green peach aphid "biotypes" to identify the factors responsible for this variation in host range."

Using a different approach, Dr Cotter is studying the highly destructive cotton bollworm (Helicoverpa armigera).

"The cotton bollworm also feeds on hosts in a number of plant families," she says, "but unlike the green peach aphid, it does not appear to form "biotypes" specialised to particular host plants."

Using a closely related species, which does not feed on legumes, Dr Cotter will compare hybrids of the two that can and cannot feed on legumes to identify the factors that allow legume feeding in the cotton bollworm.

HEADLINE | SECOND-PAGE