Many of the same pests are attacking crop
plants now as 20 years ago, but some that
were rare are common, and vice versa.
Image: iStockphoto
Climate change and other drivers are altering the make-up of Australian agriculture’s invertebrate pest populations and presenting new challenges for researchers and grain growers.
Professor Ary Hoffmann from the University of Melbourne’s Centre for Environmental Stress and Adaptation Research (CESAR) said a project comparing historical pest reports in southern Australia had revealed changes in pest outbreak patterns over the past 20 years, with some species increasing in number and others declining.
In their paper recently published in the Australian Journal of Experimental Agriculture, Professor Hoffmann and colleagues found some pest species of grains crops had become more important in recent times, while others that were important 20 years ago are now quite rare.
Professor Hoffmann emphasizes that a combination of approaches will ultimately be required to control pests in the grains industry, and that climate change adds an extra layer of complexity.
“We have to understand how pests and the beneficial species that help control them are going to respond to climate change both directly and in response to altered farming practices. We need to prepare for new emerging pests to help produce grain while maintaining low chemical inputs.”
“A comparison of pest outbreak reports from the early 1980s to 2006-07 from south-eastern Australia highlights a decrease in the importance of pests like armyworms. Others like lucerne flea, Balaustium mites, blue oat mites and Bryobia mites have increased in prominence. Parallel changes are being seen in Western Australia.”
These species are among the most important agricultural pests in Australia, attacking a variety of crop plants and often leading to entire paddocks needing to be re-sown.
“Climate change has led to drier conditions and increased temperatures, and this seems to have already impacted some invertebrate pests. For example, outbreaks of armyworms were common in the 80s, but have probably reduced as a direct effect of drier conditions.”
The build up of this migratory pest occurs when there are wet conditions in inland NSW and Queensland - conditions that allow huge populations to develop and then spread into southern areas such as Victoria. We now rarely see the weather systems that produce these wet conditions.”
Professor Hoffmann suggests that the management responses growers make in response to changing conditions are often just as important as the direct effects of the climatic conditions themselves.
“For instance, many farmers have reduced tillage of the soil as a way of conserving soil moisture as conditions have become drier. This in turn has allowed some types of pests such as slugs to thrive.”
However he indicates that there are also benefits arising from these changes.
“When soil tillage is reduced, populations of beneficial insects like predatory beetles can build up more easily, and these can suppress populations of some pests.”
The introduction of genetically modified grain crops will also undoubtedly change farming practices in the future and therefore be a future driver that may impact on pests. GM grain crops will provide new options for control, but are also likely to present challenges, as pest dynamics shift.
Incorporating GM grain crops in Australia should also reduce the number of sprays and reliance on harsh insecticides, and potentially reduce negative effects of chemical applications on non-target organisms.
Professor Derek Russell, a visiting fellow at The University of Melbourne, has been managing projects in Asia and Africa connected with cotton and later with GM crops for over 20 years.
“The rapid spread of herbicide-tolerant GM canola in Canada and soy bean in Argentina have resulted in a dramatic shift to low tillage systems with consequent water and soil conservation benefits but equally with shifts in the pest and beneficial insect complexes” says Professor Russell.
“In Australia, the introduction of GM cotton over a decade ago has led to large reductions in insecticide applications, significantly reduced the environmental impact of growing cotton and enabled the widespread adoption of Integrated Pest Management (IPM) within the industry”, Professor Russell says.
“Incorporating GM grain crops in Australia might be expected to have similar benefits and potentially reduce negative effects of chemical applications on non-target organisms”.
Editor's Note: Original news release can be found here.
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