Lentil and faba bean are key crops in southern Australian broadacre cropping. In South Australia and Victoria, lentil planting area is expecting to exceed 1M ha in 2025. This expansion in cropped area has come at the expense of barley and canola and has largely been driven by high gross margins for lentil. In some areas, lentil and faba bean are cropped in tight 1:1 rotation with wheat. As cropping frequency increases, disease pressure is expected to increase as soilborne pathogen inoculum builds up. Industry reports of poor performing lentil and faba bean crops indicates that this has been occurring already.
A DNA-based survey of pulse root diseases conducted from 2019-2020 found Fusarium avenaceum was commonly associated with poor root health, and present in approximately 23% of samples nationally. However, F. avenaceum was more common in South Australia, present in 49% of lentil and 65% of faba bean samples, and in Victoria, present in 50% of faba bean, although only 7% of lentil.
Isolates collected from samples underwent pathogenicity testing; all isolates were found to be pathogenic across a range of pulses including lentil, faba bean, chickpea and lupin. A qPCR assay was developed by SARDI’s Molecular Diagnostic Centre, where a DNA-based soil testing service routinely provides growers with risk reports for cereal root diseases (PREDICTA B).
In 2023 and 2024, field experiments were established at Pinery, SA and Horsham, Victoria to determine impacts of five Fusarium species/species complexes inoculated into field plots. In 2023 at Pinery, three isolates of F. avenaceum reduced establishment by an average of 57% in lentil (P < 0.001) and 55% in faba bean (P < 0.001) compared to non-inoculated control plots. At Horsham, the same isolates reduced lentil and faba bean establishment by 76% and 27% (P < 0.001), respectively. At Pinery, lentil and faba bean yield were subsequently reduced by an average of 68% and 49% (P < 0.05), respectively.
In 2024, inoculated field experiments were conducted to further validate results and investigate the role of inoculum level in soil and possible management options, including fungicide seed treatments. Yield reductions were similar to previous experiments, with a linear response to inoculum rate noted at Pinery. Fungicide seed treatment was effective at reducing yield loss at Pinery, but not at Horsham (P > 0.05).
A controlled environment study has identified the susceptibility of alternative host crops as well as weed species, with F. avenaceum having less impact on wheat than on barley or oats, and high impact on lentil, canola and faba bean. These six crops types are most frequently considered in the regions where F. avenaceum has been identified as a potential issue.
This research has identified Fusarium avenaceum as a substantial yield limitation in lentil and faba bean cropping in southern Australia, identified its distribution across this region, developed a tool for detecting inoculum in soil which could be used to predict disease risk prior to cropping, and identified potential management options including an effective fungicide seed treatment and rotational crop options.