Insect pests on rise

Insect pests which could become a problem include brown planthoppers, green leafhopper and additional species of stink bugs to the one in the photo, which is already a pest of brassicas in NSW.

Pest insect management already costs Australian farmers $500 million a year - and now the rules for managing pests will need to change.

According to participants in a Grains Research and Development Corporation (GRDC) workshop held this month in Orange, higher temperatures will increase the risk of crops being susceptible to pest insects and pathogens.

The workshop, organised by the GRDC’s National Invertebrate Pest Initiative, drew together 65 scientists from State government departments, universities, farmer groups and CSIRO.

NSW Department of Primary Industries (DPI) health sciences research leader, Dr David Hall, said some of the major consequences of temperature increases are expected to be:

  • Greater survival of ‘over-wintering’ pests and pathogens, meaning outbreaks will develop faster in spring.
  • Changes to the relationship between pest and predator, which will affect the effective functioning of integrated pest management strategies.
  • More generations of pests because of the higher temperature.
  • The distribution of many warm climate pests and diseases will expand southwards.

One immediate effect is likely to be more fruit flies.

Andrew Jessup, the key NSW fruit fly researcher, said fruit flies could be expected to extend their range further south and the risk of tropical pests in general would increase.

The altered range of pests is also expected to affect the rice industry.

DPI principal research scientist, Dr Mark Stevens, said with warmer temperatures in winter, pests like stink bugs are more likely to survive in vegetation surrounding rice fields, and their populations in the crop would therefore develop faster.

"Many pests of quarantine concern which do not currently occur in Australia, such as the rice water weevil, would cause more damage at higher temperatures if they were to establish here," he said.

Dr Stevens said many pests that cause problems in tropical rice environments are already present in northern Australia.

"At the moment we don’t have these pests in southern NSW," he said.

"Those which could become a problem are brown planthopper, stem borers, green leafhopper and additional species of stink bugs."

The meeting was also told that higher CO2 levels would change the carbon to nitrogen ratios in plants and this would affect insects’ feeding behaviour.

An area where the climate change impact is less certain is rainfall. Dr Hall noted the delegates said this area was more complex and the predictions of effects on pests and pathogens were a lot harder to work out.