Cropping

New podcast to help growers cope with crop disease

By Rodney Woods

This season, many cereal growers across the southern region are reporting uneven patches, bare areas, slow growth and stunted plants, yet nothing is obvious when examining plant leaves and stems.

The answer to the crops’ lack of performance may require a deeper look.

South Australian Research and Development Institute principal scientist in soil biology and molecular diagnostics, Alan McKay, said uneven crop growth could be caused by a number of factors including drought, soil structure or toxicity issues, nutrient deficiencies or soil-borne disease.

Dr McKay said mid to late winter was an ideal time to examine crop roots to assess the presence and the impact of soil-borne diseases.

“Several years of dry spring and summer conditions can be conducive to the build-up of fungal diseases such as rhizoctonia root rot, which can cause yield losses of 10 to 50 per cent in cereals,” he said.

“This disease is particularly problematic in cases where growers have planted cereal on cereals, but where high inoculum levels are present this disease may even impact pulse and canola crops.”

In a new Grains Research and Development Corporation podcast — Rhizoctonia in 2020 — Dr McKay and fellow scientist Blake Gontar discuss the disease, which is a significant issue for lower rainfall zones and lighter soils in Australia's western and southern grain regions.

“We expected rhizoctonia root rot to be an issue this year, given the seasonal conditions we’ve experienced in recent years, and particularly in paddocks where cereals were grown after cereals,” Dr McKay said.

“Sowing crops early allows the seminal root system (roots from the seed) to establish and while most rhizoctonia seed treatments provide reasonable protection of the seminal roots, they offer limited protection to the secondary roots which develop later from the crown.

“So, while the crop may get off to a good start, if these crown roots are impacted by disease, plants are limited in their ability to forage for nutrients and moisture which manifests as stunted and uneven growth across the paddock.”

Dr McKay said while there were limited actions growers could take mid-season to control rhizoctonia, accurately identifying the presence of soil-borne diseases was critical to inform decision making that could reduce the impact and financial losses in subsequent seasons.

For more information about rhizoctonia, listen to the new GRDC podcast at: https://bit.ly/338kheQ or check out the GRDC regional fact sheets at: https://bit.ly/335WYSX