Cropping

‘Watch and act’ to counter Ascochyta threat

Grain Central, June 6, 2017

CHICKPEA growers and agronomists are being advised to `watch and act accordingly’ when it comes to managing the fungal disease Ascochyta blight this season.

NSW DPI senior plant pathologist Dr Kevin Moore said there had been two recent detections of Ascochyta in southern Queensland in paddocks planted to Kyabra and the recently released PBA Seamer variety.

This follows two recent detections of Ascochyta in southern Queensland in paddocks planted to Kyabra and the recently released PBA Seamer variety.

NSW Department of Primary Industries (NSW DPI) senior plant pathologist Dr Kevin Moore recommended that all varieties, including PBA Seamer and PBA HatTrick, be sprayed with a registered Ascochyta fungicide prior to the first rain event after crop emergence.

He said many paddocks planted to chickpeas in 2017 already contained the Ascochyta fungus because they were chickpea on chickpea or because they were inoculated with wind borne infected chickpea residue during harvest of 2016 and also possibly with residue from Ascochyta-infected 2015 chickpea crops.

“This means chickpea plants will be infected during the first post-emergent rain event if they are not sprayed with a registered fungicide before that rain event,” Dr Moore said.

The initial diagnosis of Ascochyta was made by a local agronomist based on symptoms and the presence of pycnidia in leaf and stem lesions and samples were then sent to NSW DPI for confirmation.

According to Dr Moore, the crop was planted in the last week of April and received 15mm of rain in mid-May but was not sprayed with a fungicide prior to the rain.

Although the outbreak could have involved seed borne Ascochyta, Dr Moore said the multiple lesions on infected plants suggested a high level of Ascochyta inoculum was present in the paddock at planting as infected chickpea residue from the 2016 crop (i.e. chickpea on chickpea).

For years Dr Moore has warned against planting back-to-back chickpeas, saying growers risked up to 100 per cent crop losses if conditions favoured disease development.

“This case highlights one of the risks of planting chickpea back into its own residue. Other risks are Sclerotinia and Phytophthora, which unlike Ascochyta, cannot be controlled in-crop,” he said.

If serious disease outbreaks were to occur, they would pose costly and long-term implications for the entire grains industry according to Dr Moore.

“The first implication is the increased risk of the pathogen becoming more virulent and aggressive,” he said.

“Secondly, it places increased pressure on the resistance genes in new varieties as crops are subject to earlier infection and potentially more disease cycles within a season; and thirdly, we could see an increased risk of the pathogen developing resistance to fungicide.

“The resounding advice is that planting chickpea on chickpea is far too risky and the risks to the grower and the industry far outweigh any potential gains.”

Dr Moore said the best practice recommendations for disease control in chickpea crops were to maintain a 1-in-4 year rotation; avoid planting next to last year’s chickpea stubble if possible; ensure all planting seed is pickled and follow the recommended in-crop Ascochyta fungicide strategy for the variety being grown.

The Grains Research and Development Corporation (GRDC) recently released a Know More video to help growers with Ascochyta blight identification and management which is available on the GRDC’s YouTube channel www.YouTube.com/theGRDC or by following this link.

For more information, contact Dr Moore on 0488 251 866 or 02 6763 1100, fax 02 6763 1222 or email [email protected], watch the GRDC’s Ascochyta Know More video or visit the GRDC-supported eXtension AUS website www.extensionaus.com.au.

Source: NSW DPI, GRDC

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