Crop Watch September 2020

Crinkly faba beans

Physiological leaf crinkle has been observed in PBA Bendoc faba beans in the lower north, mid north and south east of South Australia this year. The affected plants also show discolouration underneath the leaf. These symptoms were also seen in 2019 on both PBA Bendoc as well as Kareema broad beans, however plants grew out of them with no apparent impact on yield.

Chocolate spot in PBA Amberley faba beans

Higher than expected levels of chocolate spot have recently been reported in field observations of PBA Amberley faba beans in Victoria, indicating that fungicide sprays could be required for disease management in this cultivar. PBA Amberley was released in 2019 with a provisional MR rating to chocolate spot. Growers should be alert and monitor their crops closely as disease development can progress rapidly over just a few days especially when the weather is warm and humid. In conducive conditions, chocolate spot can rapidly defoliate plants and severe infection can cause pod splitting and seed staining.

Diseased samples sought of pulse and canola for GRDC funded research

Diseased samples from this year’s commercial pulse and canola crops are being sought by South Australian Research & Development Institute (SARDI) research scientist Sara Blake to assist with monitoring the nature and extent of disease in 2020.

Grain growers and advisers are being asked for help in providing samples of ascochyta blight in lentil, faba bean and chickpea as well as sclerotinia in pulse and canola crops.

These samples will contribute to GRDC project investments that screen for any changes in ascochyta blight disease resistance of current cultivars, to monitor pathogen population changes and to also understand how serious a disease sclerotinia is for the southern pulse industry.

Collection kits with return envelopes will be provided to growers and advisers willing to provide samples. Please contact:

Sara Blake
Email: sara.blake@sa.gov.au
Phone: 8429 2248
Twitter: @Sara_N_Blake

Cereal disease observations

Wheat rust reports

Stripe rust

SARDI has now received multiple reports of wheat stripe rust hotspots across the state. Reports are from the following regions: the Mid and Upper North, the Yorke Peninsula, the Murray Mallee and the South East on the varieties Trojan and Scepter.

Leaf rust

SARDI have received reports of wheat leaf rust in DS Bennett from the Mallee and South East.

Net form net blotch (NFNB) fungicide resistance update

Following the discovery of SDHI resistant NFNB on the Yorke Peninsula in 2019 a further two reports of resistance have been confirmed by Centre for Crop Disease Management (CCDM) Curtin University, and are present in the South East and on the Eyre Peninsula. These are caused by three separately occurring mutations. Following a crop survey in August it is apparent that SDHI seed treatments are not controlling NFNB in some crops on the upper western Eyre Peninsula.

Oat red leather leaf (RLL)

Severe RLL has been observed in the Mid North in paddocks sown into oat stubble. Ongoing cool damp conditions will see symptoms continuing to develop.

Powdery mildew (PM)

There have been recent observations of PM in wheat and some susceptible cultivars are seeing high levels of disease in a range of regions including the Yorke Peninsula, Upper Yorke Peninsula, Upper North, and around Strathalbyn. The CCDM have now recorded fungicide resistance in this pathogen to strobilurins and tebuconazole. Many commonly grown cultivars are now susceptible to this disease and infection in the head can result in significant yield losses.

This is a timely reminder to monitor crops closely for disease development. For assistance with disease diagnosis, leaf samples can be sent to SARDI Cereal Pathology.