Field Crop Diseases

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Disease-free winter crops, save for stem rust late in the season

Figure 1 Newly-emerged chickpea at Jondaryan QLD (Photo D.L Adorada).

Figure 1 Newly-emerged chickpea at Jondaryan QLD (Photo D.L Adorada).

Disease surveillance on winter grain crops in the GRDC Northern Region showed no major disease issues from July to September 2018.

Joining with Dr. Kevin Moore, a chickpea pathologist from NSW-DPI (Figure 1), more than 60 chickpea crop paddocks across central Queensland, southern Queensland and northern NSW were visited. Very few paddocks with ascochyta blight, botrytis seedling disease, phytophthora root rot and virus infection were observed during the survey (Figure 2), leaving little to worry about. Lack of moisture was the major issue observed.  However, this most likely contributed to the lack of disease as most pathogens need moisture to infect plants.

Figure 2 (a) Ascochyta blight on chickpea at Lonesome QLD (Photo D.L Adorada).

Figure 2 (a) Ascochyta blight on chickpea at Lonesome QLD (Photo D.L Adorada).

Figure 2 (b) Sclerotinia stem lesions on chickpea at Lonesome QLD (Photo D.L Adorada).

Figure 2 (b) Sclerotinia stem lesions on chickpea at Lonesome QLD (Photo D.L Adorada).

Of the wheat crop paddocks inspected, very low incidence of yellow leaf spot in two paddocks in southern Queensland was observed. This was most likely brought about by inoculum left from the previous year’s stubble. A paddock in central Queensland had very low incidence of a suspected phytophthora root rot infection.

Of the barley crop paddocks inspected, only one paddock was seen to have spot-form net-blotch (SFNB) (Figure 3) infection on the lower leaves at flowering stage. No fungicide spray was applied as incidence and severity were low and the disease would not cause significant yield loss.

Figure 3 Spot-Form Net Blotch on Barley lower leaves (Photo D.L Adorada).

Figure 3 Spot-Form Net Blotch on Barley lower leaves (Photo D.L Adorada).

Figure 3 (b) Spot-Form Net Blotch on Barley lower leaves (Photo D.L Adorada).

Figure 3 (b) Spot-Form Net Blotch on Barley lower leaves (Photo D.L Adorada).

Winter grain crops seemed headed towards at least average yields in spite of the dry conditions. However, after continuous October 2018 rain in southern Queensland there was a sudden outbreak of barley stem rust (Figure 4), particularly in the areas of Brigalow, Jandowae, Chinchilla, Dalby, Brookstead and Toowoomba. Samples sent to Professor Robert Park (University of Sydney) for pathotyping revealed that isolates were the Scabrum rust pathotype which is often observed in Queensland.

Figure 4 (a) Barley stem rust on QLD barley varieties (Photo R. Wood).

Figure 4 (a) Barley stem rust on QLD barley varieties (Photo R. Wood).

Figure 4 (b) Barley stem rust on QLD barley varieties (Photo R. Wood).

Figure 4 (b) Barley stem rust on QLD barley varieties (Photo R. Wood).

Figure 4 (c) Barley stem rust on QLD barley varieties (Photo R. Wood).

Figure 4 (c) Barley stem rust on QLD barley varieties (Photo R. Wood).

To prepare for the upcoming winter season, barley growers are encouraged to promptly implement control measures for weeds and crop volunteers to reduce the chances of costly disease issues like barley stem rust.

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