Vigilance the word for Ascochyta Blight

Image of Ascochyta blight in a lentil crop

Ascochyta blight in a lentil crop.

PHOTO: Rohan Kimber

Growers who have planted back-to-back lentils or tight lentil rotations this season are urged to monitor crops closely for ascochyta blight during August, particularly if a wet winter prevails.

The need to monitor crops for ascochyta blight in this period is particularly important following research that identified changes in the aggressiveness of ascochyta blight.

These changes led to the loss of effective resistance to ascochyta blight in the previously widely grown NipperA variety four years after its commercialisation.

The research was co-funded by the GRDC and the South Australian Grain Industry Trust and was undertaken by the South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA, and the University of Melbourne.

The finding is significant because although Nipper has now reduced in popularity, in 2012 it accounted for 20 per cent of the total lentil area in southern Australia and reached as high as 30 per cent of the lentil area on SA’s Yorke Peninsula.

Now, PBA Hurricane XT, which also has genetic resistance to ascochyta blight and boasts a range of other agronomic advantages such as Group B herbicide tolerance, has taken over as one of the more popular varieties. There are predictions it could make up 50 per cent of the Australian lentil area in the future.

The research suggests that widespread planting of lentil varieties with Indianhead parentage, including PBA Hurricane XT, PBA Ace, PBA Bolt and PBA Herald XT, could lead to a similar outcome to that observed in Nipper.

Ascochyta blight affects grain yield and quality through seed abortion and seed staining.

SARDI senior pulse pathologist Dr Jenny Davidson says if growers observe symptoms of ascochyta blight in PBA Hurricane XT and PBA Jumbo2, they should send leaf samples to SARDI. 

“Growers should be monitoring crops closely, particularly in August if we have a wet winter, and implementing a foliar fungicide program,” Dr Davidson says.

“In high-risk areas such as the Yorke Peninsula, those growing susceptible to moderately susceptible varieties such as PBA Flash and Nipper need to do a vegetative spray if ascochyta blight is present in order to hold the disease back.

“Following that, growers need to monitor all lentil crops during flowering and podding. Anything with susceptibility in the crops would need to be sprayed during podding if ascochyta blight is present.”

Dr Davidson says growers would also need to be spraying fungicide ahead of rain events during spring.

For botrytis grey mould, Dr Davidson says all lentil crops should be sprayed at canopy closure or immediately before closure to protect against the disease.

Subsequent sprays, she says, will depend on spring rainfall. 

More information:

Dr Jenny Davidson
08 8303 9389

Dr Rebecca Ford
Griffith University

End of Ground Cover issue 123 (southern edition)
Read the accompanying Ground Cover Supplement:

'More Profit from Crop Nutrition II'

GRDC Project Code DAS00139

Region South