Oat foliar disease management and control
Gone are the days of oat being considered the poorer cousin of wheat and barley.
Increased values and yields are proving that the grain is worth looking after to ensure maximum performance and avoid hefty downgrades. Elders Narrogin agronomist Helen Wyatt explains the best strategies to manage foliar disease and maximise yield and quality.
The main drivers of oat variety selection are yield, grain hectolitre weight and/or hay quality.
In milling grain oats (OAT1/OAT2), falling out of specification guides, especially weight, can result in very large price penalties and potentially limit your market size.
Across many key growing regions in Western Australia this has led to a large uptake of Bannister oats (approximately 40 per cent), for its high yield and good reliable grain weight. This variety is however susceptible to Septoria which can cause gran staining in high pressure scenarios, and consequent downgrade at harvest. In hay crops, Septoria can affect colour and hay quality.
To best control Septoria, management every year with a foliar fungicide is advised. You can also further reduce the risk by mixing up the rotation and variety of crops – avoiding planting oats on oats, and burning stubble to reduce inoculum.
Both stem and leaf rust require management in both grain and hay crops too, however newer varieties have genetics with greater rust resistance (see table below) and their presence requires a green bridge over summer which varies season to season.
The risk of rust can be decreased by controlling summer weeds/volunteers – although don’t forget that spore movement on wind can still bring the disease in. In hay crops, bacterial blight is another disease that can degrade quality and is primarily controlled by rotating to non-host crops and burning stubble.
A two-spray regime at stem elongation and flag emergence will achieve the greatest benefit for Septoria in grain oats, when disease pressure is high early in the season. When disease pressure is lower, or when disease enters the canopy later in the season, a single application at flag leaf emergence is the best strategy.
Rainfall between grain-fill and harvest can also result in grain staining in Bannister, but applying late fungicides has proved unreliable. In hay, oats where Septoria occurs at early growth stages, fungicide applications around stem extension can reduce development of disease in the lower canopy and therefore spread into the upper canopy.
Fungicide application following flag leaf emergence is recommended to protect the upper canopy from disease development during head emergence and flowering. It will lead to greater retention of green leaf area for optimum hay quality – growers applying at this stage must be aware of cutting/grazing withholding periods. Fungicide application for rust is best applied once the disease is identified (it often begins in hotspots) but before the infection becomes too widespread.
The choice of fungicide will depend on the level of infection and disease/s present. Rotating chemistry, especially where a two-spray strategy is used in one season to reduce the risk of fungicide resistance, is extremely important. See the table of registered products below.