Summer crop paddocks across northern New South Wales, southern Queensland and central Queensland, were surveyed to monitor fungal and bacterial diseases present in the 2018-2019 summer cropping season. In comparison to the 2017-2018 season, it was drier (Figure 1), making it unfavourable for most grain crop diseases to develop. Observations for maize, mungbean, sorghum, soybean and sunflower are given below.
Most maize paddocks surveyed were free from disease except for:
- One paddock in Jondaryan with low incidence of common boil smut (Ustilago maydis)
- One paddock in northern NSW heavily infected with grey leaf spot (Cercospora zea-maydis)
Due to dry conditions and rains too late in most locations, fewer mungbean crops were planted than usual.
The diseases that were most commonly observed were:
- Tan spot, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens was found in low to moderate incidences (1-30%) in southern Queensland, due to favourable dry and hot weather
- Gummy pod was present in a few paddocks in southern Queensland (25% incidence) and northern NSW (15% incidence)
- Fusarium wilt at low incidence (<5%)
Precipitation played an important role in disease incidence in sorghum. Northern NSW and central Queensland had enough soil moisture at post-flowering which saved the sorghum crop from diseases induced by moisture stress, charcoal rot (Macrophomina phaesolina) and Fusarium stalk rot (Fusarium spp.).
In contrast, in southern Queensland, where there was low or no precipitation during the post-flowering months of mid-January to mid-March, high levels of stalk rots, particularly charcoal rot was observed.
Charcoal rot was prevalent in Dalby, Chinchilla, Bowenville and MacAlister, whereas incidence of Fusarium stalk rot was high in Dalby and MacAlister, albeit at low levels in most of the paddocks surveyed.
A paddock in Clermont central Queensland was heavily infected by black mould, caused by several species of dark pigmented fungi such as Alternaria, Aspergillus, Curvularia and Penicillium. Infected seeds will have reduced quality, size, viability and storage life. Prolonged periods of warm, wet weather favours development of this disease (English et al, 2005).
Soybean crops were planted only in a few irrigated paddocks.
No disease issues were present on the crop paddocks surveyed in Bongeen, southern Queensland.
Very few sunflower crops were planted due to limited rains, thus too late for commercial plantings in most locations.
No disease issues were found or reported from the sunflower paddocks that were surveyed in central Queensland (2 paddocks), southern Queensland (5 paddocks) and northern NSW (1 paddock).
What can be done
In preparation for the next summer cropping season, the best disease management option is to practice preventive measures, to minimise incidence of the disease. Disease management options are described in the following resources:
Click here for disease diagnostic support
Precila Gonzales, USQ Centre for Health
Vicki Green, GRDC
Agronomists and growers from NNSW, SQ and CQ
English M, Cahill M, Grains Research and Development Corporation (Australia), Queensland. Department of Primary Industries and Fisheries, 2005, Sorghum disorders: the ute guide, Queensland : Dept. of Primary Industries and Fisheries