Rhizoctonia root rot (Rhizoctonia solani AG8) is a fungal pathogen that damages the roots of seedlings preventing the uptake of water and nutrients, causing stunted plant growth. In the paddock its presence is typically seen as a circular depression in the crop with a sharp edge. Within patches plant numbers may be decreased (at worst, to zero) and growth (height, tillering and vigour) may be slightly to severely reduced. Rhizoctonia patches range from less than a metre to several metres across. Patches are sometimes elongated in the direction of sowing. Odd shapes also occur and patches can coalesce.
Rhizoctonia (AG-8) can attack all crops grown in the agricultural region of Western Australia but most commonly affects cereals (in the order of barley, then wheat, then oats) and legumes (for example, lupins and pasture legumes). Canola can mitigate rhizoctonia so that it is reduced in the following crop. The incidence of rhizoctonia patches in a paddock may be from negligible to greater than 30% by area. Within the patches however, grain yield is significantly reduced (usually it is zero), as the few plants that do put out a head often lodge or contain small, immature grains that are lost in machine threshing.
That patches recur in a similar position over more than one season has been confirmed by previous studies. However, patches can migrate or completely disappear over time.
This project aims to ameliorate rhizoctonia root rot by developing a tool that can be used by farmers to develop a VR approach to applying fungicide at sowing to control this disease.
- Map rhizoctonia occurrence from season to season in selected paddocks using an unmanned aerial vehicle (UAV).
- In collaboration with ThinkSpatial, develop an automated program to identify and map rhizoctonia patches at a paddock scale.
- Develop a process by which clusters of patches in a paddock can be identified as economically viable to treat.
- Analyse farmer yield monitor data to determine if this could also be used to map rhizoctonia occurrence across paddocks.
Results so far:
- Harvest plant cuts were taken from rhizoctonia patches and nearby healthy crop to provide grain yield data. These showed that across all sites 2014 and 2015 the yield loss from rhizoctonia patches was high, ranging from 37-80% and in a farming situation with machine harvest, losses in patches would be closer to 100% as most tillers lodge. Grain quality in barley was also compromised by rhizoctonia; there were significant increases in screenings and significant decreases in grain brightness and size.
- A desktop study of the economic benefit to growers has shown that at the current fungicide cost and with a grain price of $230/t then treating rhizoctonia will return $6/t/ha where 10% of the treatment area is affected by rhizoctonia (assumes 80% yield penalty in rhizoctonia patches and that fungicide is applied in a variable rate manner so that only economically responsive crop areas plus a buffer, are treated). A 2015 Grains Research and Development Corporation Regional Cropping Solutions Network trial at Ravensthorpe returned a benefit of $18/ha ($11/t/ha) for a blanket fungicide application to control rhizoctonia.