Wet start to the growing season could increase disease risk

Countryman
Spot form net blotch (Pyrenophora teres f maculata) affecting barley plants.
Camera IconSpot form net blotch (Pyrenophora teres f maculata) affecting barley plants. Credit: Luise Sigel

A wetter-than-average start to the grain growing season in WA could cause an increase in crop disease levels in coming months, with growers urged to be on the look-out for sclerotinia and spot form net blotch in crops.

Two new research projects have been launched to increase knowledge and information relating to two key crop diseases and help grain growers with disease management and reduce yield losses.

The projects aim to address spot form net blotch of barley in low rainfall areas and sclerotinia stem rot in narrow-leaf lupin crops.

Grains Research Development Corporation has invested in the five-year projects led by the Department of Primary Industries and Regional Development. GRDC crop protection manager — west, Georgia Megirian said while considerable research had already been undertaken into sclerotinia in canola crops, there was “only limited information” available about the impact and management of sclerotinia in pulse crops including lupins.

“In recent years, sclerotinia has become a significant disease of narrow- leaf lupin in WA, driven by factors including the frequency of lupin within crop rotations and seasonal conditions,” she said.

Ms Megirian said observations in the field suggested sclerotinia behaved differently in pulse crop species compared to how it behaved in canola crops. She said the new research investment aimed to provide growers and advisers with data about the impact of sclerotinia in lupin crops.

“It will also provide a better understanding of how management practices influence disease development,” Ms Megirian said.

“For example, lupin crop canopies differ to canola canopies, which potentially has implications for the micro-environment and subsequent development of disease.

“Therefore, modifying cultural practices such as increasing the crop row spacing, lowering plant densities and altering the sowing time have the potential to provide disease control and reduce reliance on fungicides.”

Ms Megirian said the SFNB of barley investment aimed to provide growers and advisers in WA’s low rainfall areas with information to inform their decision making on how to manage this disease.

In recent years, sclerotinia has become a significant disease of narrow- leaf lupin in WA, driven by factors including the frequency of lupin within crop rotations and seasonal conditions.

Georgia Megirian

“Extensive research has already been conducted into SFNB in the State’s higher rainfall zones, leading to best practice management strategies being developed for these areas,” she said.

“However, in low rainfall zones there is a lack of knowledge about the factors that will cause outbreaks of SFNB and economic losses.

“Hence, growers tend to use a prophylactic approach, such as ‘insurance’ sprays, to cover envisaged risks – which increases production costs and increases the risk of fungicide resistance developing.”

Ms Megirian said the primary source of SFNB was inoculum contained in barley stubble.

“The persistence of stubble is therefore a critical factor influencing the amount of inoculum available to infect barley crops,” she said.

“The current recommendation to growers is there should be two ‘break’ years between barley crops to reduce the risk of SFNB re-infection.

“However, environmental conditions in the low rainfall zone means there may be a reduced risk of stubble decomposition and SFNB spore release infecting subsequent barley crops.”

Ms Megirian said the investment would help industry to understand how modifying cultural practices, such as stubble management or altered sowing time, have the potential to provide some disease control and/or to allow reduced fungicide use.

The SFNB of barley investment will also provide data on the economic and disease impact, including regionally relevant economic thresholds.

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