Harvesting into the future

At a glance

• Spatial models are being used to track aphid movements to predict future impacts.
• Early results indicate barley yellow dwarf virus may have reduced impact, but more research is required.
• Future studies will look at Victoria.

Victorian scientists are investigating the impact of a changing climate on farm biosecurity and the productivity of future wheat crops.

Using existing data, scientists are building spatial models to predict how climate change will affect aphid behaviour, the barley yellow dwarf virus and ultimately wheat production.

The challenge

DPI modeller Dr Jean-Philippe Aurambout

Barley yellow dwarf virus can reduce yields in wheat by up to 25 per cent or $1.2 billion dollars over a 10-year period, according to DPI scientist Jean-Philippe Aurambout.

And little information is available on what it may do in the future under projected climate scenarios.

“Climate change is triggered by an increase in the atmosphere of greenhouse gases, mainly carbon dioxide,” Dr Aurambout said.

“Carbon dioxide is also food for crops and if water, nutrients and temperature are not a limitation, wheat could grow better under elevated CO2 than under current concentrations.

“But we also know that with climate change the rainfall will vary and yields may be lower.”

Dr Aurambout said the impact on insects and pathogens further complicated the situation because aphids and other insects respond differently to changes in climatic or environmental conditions.

“Right now we cannot just guess what will happen with yield. That is why we need computer models because they help assemble all the available data and allow us to look at various interactions and test different scenarios,” Dr Aurambout said.

Barley yellow dwarf virus is typically brought in by aphids, which move from pastures onto wheat crops as they emerge.

Dr Aurambout said the aphid and the barley yellow dwarf virus were the focus of the study.

“We have three players and the theatre is the crop and the climate.”

The models

FIGURE 1 - Illustration of the structure of the wheat/aphid/BYDV model (from Parry et al. 2011). Aphids move away from irrigated grasses into wheat patches where they can start an infection of Barley Yellow Dwarf virus

What do the models do?

“Our model looks at how the climate impacts on wheat, so how quickly the wheat will grow and what we should expect,” explained Dr Aurambout.

“It also looks at the aphid to see when it moves from the surrounding grassland to the wheat, which is when we will have outbreak problems.”

The models (see Figure 1) consider each of these parameters and apply them to possible future climatic conditions, using projections from the CSIRO atmospheric sciences.

“The model is designed to be applicable to any region, providing the data is available,” Dr Aurambout said.

He said the model had been run in regions in South Australia and Western Australia because this is where DPI and their CSIRO collaborators had access to existing aphid population data to compare results.

To improve predictions for Victoria, further research is required on aphid population data on local wheat crops.

“When you develop a model it cannot be applied until it is validated,” Dr Aurambout said.

Validating involves comparing the model’s predictions with data already recorded.

“In order to provide a better answer for farmers and the grains industry, we need to investigate the full range of possibilities.”

The results

Two years into the study the initial results are encouraging.

“With increased temperatures, the aphids leave the grassland later, which means they arrive later on the wheat,” Dr Aurambout said.

He said this meant the aphid and virus were less likely to make a substantial impact on production levels.

“If aphids arrive when the wheat is emerging, transmission of disease is the highest. But if the aphids arrive later, the impact of the disease will be minimal.”