Leaf rust in wheat. Crop volunteers and weeds provide an ideal host for diseases like rusts which can rapidly spread to newly planted winter crops.
Grain growers across Queensland and New South Wales can be winter crop ready and avoid costly winter pest and disease issues by taking immediate action against weeds.
The Grains Research and Development Corporation (GRDC) is urging growers to control crop volunteers and weeds now and heading into autumn to reduce the risk of serious insect and disease damage to 2016 winter crops and avoid costly control measures.
Commonly known as the `green bridge’, crop volunteers and weeds provide an ideal host for insects and diseases which can rapidly spread to newly planted winter crops.
The risk is particularly prevalent for foliar cereal diseases such as rusts, especially in years when summer/autumn rainfall has resulted in a significant green bridge in paddocks or along headlands, roadways and other non-crop areas.
Spores are windborne and easily spread - as little as one infected leaf per 12 hectares of regrowth surviving through summer and early autumn can cause a rust epidemic in the following cereal crop.
According to the GRDC, outright kill of weeds and volunteers is the only way to guarantee they won’t play host to pests and disease. However, given the spores’ propensity to travel, effective control requires neighbours to undertake a coordinated management plan.
Department of Agriculture and Fisheries (DAF) principal pathologist Greg Platz said the occurrence of stripe rust and leaf rust in certain wheat and barley varieties during the 2015 season reinforced the need to implement an integrated control strategy ranging from weed control to variety selection.
“If high levels of rust are present in a green bridge when crops are sown, even varieties selected for their rust resistance may become heavily rusted,” Mr Platz said.
Resistance ratings for cereal rusts are usually based on adult plant responses. Yet with stripe rust, varieties with good adult plant resistance may be quite susceptible during tillering, according to Mr Platz.
“Heavy infection early in crop growth can challenge resistance at the adult stages. Controlling the green bridge and sowing resistant varieties offer the best means of avoiding serious yield losses to disease,” he said.
“Growers should keep abreast of the National Variety Trials (NVT) disease ratings as changes in pathotypes in one growing season can have major implications for varietal selection in the following season.”
The advice coincides with the recent confirmation that a new strain of wheat leaf rust detected in southern Australia in 2014 has now reached Queensland.
Mr Platz said once the winter cropping season began, it was imperative that growers regularly monitor crops for any signs of disease and apply fungicides as required.
“The impact of diseases on yield and quality varies with the severity of the disease, duration of the disease epidemic, resistance levels in the host variety and environment,” he said.
“It is difficult to be prescriptive as to when to spray but the more susceptible a variety is, the sooner it should be sprayed.
“Growers should manage the risks early, be aware of how crop varieties performed under disease pressure in 2015, keep up to date with NVT disease ratings and monitor closely as the season progresses.”
DAF Manager (Media)
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Sarah Jeffrey, Senior Consultant Cox Inall Communications
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