Dry cropping season prompts cereal root disease alert

Cereal root disease alert

Cropping
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Graingrowers in the southern cropping region who have experienced a dry growing season this year are being warned of a potential increase in the risk of some soilborne diseases in 2019.

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NEW INFO: Attending the PREDICTA® B Root disease risk management course for agronomists were Western AG's Clare Svilans, Kaniva, Vic, and YP Ag's Luke Harrop, Kadina.

NEW INFO: Attending the PREDICTA® B Root disease risk management course for agronomists were Western AG's Clare Svilans, Kaniva, Vic, and YP Ag's Luke Harrop, Kadina.

Graingrowers in the southern cropping region who have experienced a dry growing season this year are being warned of a potential increase in the risk of some soilborne diseases in 2019.

Rhizoctonia root rot and crown rot are two cereal diseases likely to pose a problem in parts of SA and Vic where rainfall was below average this year.

A lack of rainfall has reduced the breakdown of cereal stubbles in pulse and oilseed break crops, promoting the risk of disease next season.

Soilborne disease experts are advising growers to know their paddocks’ disease risk profile well ahead of sowing in 2019 by having their soils tested.

Leader of SARDI’s soil biology and molecular diagnostics group Alan McKay said the risk of disease in 2019 would be heightened where growers decide to sow wheat back into this year’s failed wheat crops.

“I expect rhizoctonia and crown rot will be the main issues as a result of low growing season rainfall, and growers should also keep an eye on cereal cyst nematode as levels have been trending higher over the past five years,” he said.

“Rhizoctonia, especially, has a competitive advantage in low moisture situations and its levels have almost certainly increased this year. It survives best when there is no summer rainfall and therefore reduced soil microbial activity.

“If we do experience a dry summer and the break to the season is late, crop seedlings will be exposed to high levels of rhizoctonia next year.”

Rhizoctonia root rot can reduce cereal yields by more than 50 per cent, with barley being the most susceptible.

Dr McKay said development of the PREDICTA® B soil testing service for rhizoctonia has been a success in enabling pathogen levels to be effectively monitored to inform growers’ paddock planning.

Testing for crown rot ahead of sowing in 2019 is also being strongly encouraged.

SARDI research scientist Marg Evans said although crown rot requires moisture in autumn to infect the crop, a dry spring such as the one experienced this year will favour expression of the disease.

“The fungus grows quicker in water-stressed plants and in warm weather, and damage is more likely in intensive cereal rotations, especially in durum,” she said. 

Whiteheads can be symptomatic of crown rot but given these only appear in seasons with a dry finish, the absence of whiteheads does not indicate freedom from crown rot.

“That is why it is so important to know what is happening in the paddock,” Dr Evans said.

Crown rot survives for up to four years in plant residue/stubble and infection occurs when plants come in close contact with infected residues.

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