Understanding Sclerotinia Risks Associated with Growing Peanuts in the South Burnett Area
by C.M Pepper, CQ University, Australia
Introduction
The South Burnett area in Queensland is the largest production region for peanuts in the State, and is therefore of national significance for agriculture in Queensland.
- the South Burnett area produces around 90% of Australia’s peanuts1
- crop yields in the region are commonly in the range 1.5 to 4.0 tonnes per hectare1
- peanut yield losses range around 10% and in some cases of severe disease outbreaks can cause yield losses of up to 50%2
The fungal pathogen Sclerotinia minor is a major threat to peanut production in the South Burnett, where in the 2017/18 summer growing season a widespread outbreak of the disease resulted in significant losses in farmers' crops.
Sclerotinia sp. are one of the hardest groups of fungal pathogens to manage in agricultural production systems, as the pathogen only occurs when environmental conditions are favourable, making it difficult to manage each season.
Aims
- To evaluate the severity of the Sclerotinia in the South Burnett area.
- To verify the potential of South Australia Research and Development Insitute (SARDI) new PreDictaB Test for Sclerotinia.
- To identify Sclerotinia risks only associated with growing peanuts.
- To develop a pre-season risk platform that will assist growers in peanut seed sowing decisions.
- To establish if correlations exist between the soil-borne disease incidence/severity and agriculture practices used in the region.
Methods
- Survey of 19 paddocks where peanuts were grown in the 2017/18 season
- Identify relationships between:
- disease severity
- pre-planting soil inoculum levels
- growers’ agricultural practices
- weather conditions.
- Paddock survey using pre-planting assessment tool PredictaB test –specifically S. Minor analysis.
- Polymerase chain reaction (PCR) extraction method of DNA from the soil sample; positive and negative results indicating presence of the disease or not.
- Average detection of Sclerotinia kDNA copies are graphed against the severity observed in the paddock.
Results
High proportion of peanut growers’ paddocks were identified to have moderate to high levels of disease inoculum in the soil – potentially leading to infection of plants and significant damage to crops in the South Burnett.
PreDictaB test by SARDI appears an useful tool to identify pre-planting risks for peanut crops and other susceptible plants. Soil inoculum levels shown to be an important indicator of the risk the disease poses, but other factors also influence the development of the disease in the peanut bush, such as soil type.
The risk matrix (below) is a resource to be used once a PreDictaB soil test has been conducted. Inoculum level results are converted to a Log value to produce an inoculum rating 1 to 4 (values greater than four are possible, but were not detected in this study).
The results from the PreDictaB assessment suggested that pre-plant inoculum levels of more than 1000 kDNA/g soil, or a log rating of four, were very likely to lead to severe disease damage in crops.
Sclerotinia risk matrix
Key: Green – low/nil risk, Yellow – medium risk and Red – high risk (potentially high plant death rate if peanuts were to be planted)
Conclusion
- The data collected and recorded suggests that weather patterns, soil type and peanut variety can interact and cause Sclerotinia to appear in the paddock.
- Heavier soils possess a higher susceptibility risk than lighter soils
- Intense and constant rain periods promote the occurrence of the pathogen greatly
- Through conducting more PreDictaB soil tests and gathering more data, the accuracy of this test can be validated, thus ensuring the efficiency of this resource that growers and advisors can utilise to make well-informed pre-season planting decisions.
- Further research is required to identify management strategies for Sclerotinia in peanuts, such as trials for new chemicals, alternative agricultural practices and nutrients to control its presence.
Acknowledgments
Thank you to Northern Agriservices and Peanut Company Australia (PCA) for providing the opportunity to investigate an issue within the South Burnett area and providing support in doing so.
References
- Wright, G., L. Wieck and D. O’Connor (2017). Peanut Production Guide Peanut Company Australia (PCA).
- Maas, A., K. Dashiell and H. Melouk(2006). "Planting Density Influences Disease Incidence and Severity of Sclerotinia Blight in Peanut." Crop Science46(3): 1341-1345.
Other resources
