Entomologist's bug warning for farmers as the climate gets warmer

It’s not quite a horror movie but insects with faster growth rates, increased reproduction and less likelihood of being killed during winter are a scary prospect for crop farmers in Tasmania.

Tasmanian Institute of Agriculture entomologist Dr John Finch spoke at the field day at Forthside Vegetable Research Facility on Tuesday and sent a clear message to growers that climate change is great for bugs and that could result in a productivity drop by up to 20 percent over the next 50 years.

“Because climate change is happening and we’re seeing increased temperatures, changes in rainfall patterns and more Co2 in the air, insects will respond to all of those things and became more problematic than ever before,” he said.

“More Co2 means plants take it in and grow more and the relevant amount of nitrogen decreases in their tissues – that means the insect has to eat more material to fill that nitrogen deficit, so they do more damage.

“It’s a bit like an athlete switching from eating a high protein diet to living off pasta – they must eat more pasta to get enough protein.

Dr Finch said that at the moment a lot of pests are controlled by predators like ladybirds, but when environmental conditions change, the predators respond different to the pests and they become de-coupled.

“All of this put together means it’s likely we’ll see increased pest pressure in the future and lower yields,” he said.

Dr Finch said that as an island state Tasmania has some advantages with a more reliable rainfall than the mainland and a natural border that keeps out some of the worst pests.

He said another advantage is that we’re always changing crops and that doesn’t give the bugs one uniform thing to do. 

However he believes that the ban on GMO crops is a disadvantage as that is likely to be a key tool in the future for managing pest numbers.

“I think we should be looking at everything in the toolbox to maintain productivity in the future,” Dr Finch said.

“We’re looking at a 2-4 degree temperature increase that is going to devastate the agricultural system so you really need everything possible to allow growers to adapt as quickly as possible to that changing landscape.”

Some of TIA’s research is around what can be planted as a “trap crop” to protect raspberries and other berries – something to intercept the march of bugs when the grass dries off in January and February and they seek out irrigated crops.

“However this method relies on giving up some land to grow the trap and the jury is still out on if that’s an economic option,” Dr Finch said.

Intercropping is another option, and researchers are trialling the integration of a crop of pyrethrum with potatoes to see if that slows down the spread of the pest.

“Forecasting will also come to the fore to give growers advance warning that these things are going on – such as sampling the air to see what’s flying around, model how crops grow by thinking about temperature, water and soil and model how insects grow by thinking about temperature again,” he said.

“But what we really need to do in the future is put those models together so they can talk to each other and that’s going to allow us to predict things in advance and let growers know so they can take evasive action.

“I can see a day when a farmer wakes up in the morning and receives a text message to say ‘this insect is on the move’ and they’re advised to do something about it.”