The 2022 growing season has provided a range of challenges for growers and these will continue to have an impact into 2023. Crops that have had severe disease infections are likely to have grain quality impacts and carry disease inoculum into the next cropping season.
Considerations for harvest and grain use in 2023
Many crops will have discoloured and small or shrivelled grain due to multiple diseases. Recent testing of a heads from a small number of cereal crops has revealed a combination of rust, Septoria nodorum blotch, Fusarium head blight and field fungi. The relative importance of each of these varied depending on local climate and fungicide history for the season. The effects of these fungi will likely vary significantly between crops and may result in downgrading or rejection of some grain loads at receival. It will be important to remove as much of the small and damaged grain during harvest as possible to maximise grain quality.
Feed quality
Growers will need to consider the end use of the product. There is the potential for reduced feed quality given the seasonal conditions during 2022. The conditions have also been ideal for the development of fungi. This includes fungi that produce toxins which can have a negative impact on livestock. Testing grain and hay for feed quality and mycotoxins will allow grain at risk of causing adverse animal health and productivity impacts to be identified and avoided. Lupin crops that had Phomopsis infections will be at risk of causing lupinosis in sheep. For further information on Phomopsis see Phomopsis Stem and Pod Blight of Lupins.
Disease carryover and considerations for 2023
There is an increased risk of disease carryover into 2023 for all crops. The risk will depend on the carryover mechanism of each individual pathogen but they can be broadly categorised into one or more of the four groups below. See tables 1 & 2 below for a summary of key diseases and their transmission mechanism in Victoria.
- Stubble-borne diseases predominantly survive on plant debris. These include Crown rot, Septoria tritici blotch, Ascochyta blight, and Net blotches. Crop rotations provide an excellent break for these diseases – avoid sowing back into stubble from the same crop from the last two years. Time of sowing is also important – consider sowing at risk paddocks later in the program (mid-late May).
- Volunteer plants: most diseases can carryover on volunteer plants or weeds, however, for rusts and non-seed borne viruses this is the main form of carryover. This also includes insects which transmit these viruses. Control of the Greenbridge 6-8 weeks prior to sowing can provide an important break for these diseases.
- Seed-borne diseases can infect the grain and are then transmitted to the next crop via this infected seed. These diseases include fungal diseases such as Ascochyta blight and Botrytis grey mould, bacterial blights and viruses such as Pea seed-borne mosaic virus and Cucumber mosaic virus. To find out more about seed-borne viruses see the chapter Viruses of Field Crops.
- Seed contamination: These are caused by diseases that develop sclerotes (eg Sclerotinia white mould and Botrytis grey mould) or other seedlike structure such as Ergot in wheat which can contaminate harvested grain. Sclerotes are small black granules that can range in size from less than 1mm to more than 10mm in diameter. Sclerotes can easily mix with grain when harvesting as they are a similar in size. Some sclerotes may be screened from grain, but they can often be difficult to remove. There are reports of sclerotes surviving up to 15 years with even broken or damaged sclerotes able to reinfect subsequent crops. Growers are advised to sown the cleanest seed available and avoid carrying disease into paddocks that have not yet been affected by this disease. Ergot is rarely seen in Victoria. To find out more about Ergot please visit CropWatch – Ergot in wheat.
Other factors
Seed quality will also be impacted by disease and potentially impact emergence and vigour next season. To reduce the impact of disease, sow the healthiest looking seed, and avoid shrivelled and stained seed where possible. For disease specific information see Identification & Management of Field Crop Diseases in Victoria.
Testing for general seed quality and vigour can also help. See Testing of farm-retained and carryover seed. The GRDC has also released a paddock practices guide to help growers understand the potential impact of a wet harvest. See Paddock Practices: Wet harvest implications and resources.
Seed testing
Commercial testing services that test seed for fungal infections include Crop Health Services (Ph: 03 9032 7515) for samples from Victoria (sample submission form attached) and SARDI seed and crop testing (Ph: 08 8429 2214) for samples from South Australia.
Crop Health Services (Vic): Diagnostic services | Agriculture Victoria
SARDI seed and crop testing (SA): Seed and crop testing – PIRSA
Broadacre seed testing DA FORM 13 CHS Specimen Submission Form_V1
Table 1: Common fungal disease carry over of pulses (for viruses see Virus chapter)
| Transmission mechanism | Pulse crops |
|---|---|
| Seed contamination | Botrytis grey mould Sclerotinia |
| Seed-borne | Ascochyta blight Botrytis grey mould Viruses |
| Stubble | Ascochyta blight Botrytis grey mould |
| Volunteers/weeds | Rusts Viruses |
Table 2: Common fungal disease carry over of cereals (for viruses see Virus chapter)
| Transmission mechanism | Wheat | Barley |
|---|---|---|
| Seed-borne | Fusarium head blight Crown rot | Scald Net form of net blotch |
| Stubble | Yellow leaf spot Septoria leaf blotch Fusarium head blight Powdery mildew Crown rot Take-all | Scald Net form of net blotch Spot form of net blotch |
| Volunteers/weeds | Rusts Yellow leaf spot Septoria leaf blotch Powdery mildew | Rusts Scald Net form of net blotch Spot form of net blotch Powdery mildew |
| Seed contamination | Ergot |
Further information links
Identification and Management of Field Crop Diseases in Victoria
Acknowledgments
Thank you to Mark McLean (Agriculture Victoria, Senior Research Scientist – Field Crop Pathology) and Joshua Fanning (Agriculture Victoria, Research Leader – Plant Pathology) for their contributions and expertise.
The author wishes to acknowledge the funding provided by Agriculture Victoria and the GRDC that allows this work to occur. This information has been generated by the GRDC funded project DJP2103-005RTX and the Agriculture Victoria funded project, CropSafe.
