Blackleg, caused by the fungus Leptosphaeria maculans, is the major disease of canola (Brassica napus) in Australia. The development of blackleg-resistant B. napus varieties has been a major factor in the resurgence of the industry nationwide. The main sources of resistance used in Australian public breeding programs are Japanese spring varieties and French winter varieties. In these programs, all early generation material is screened in field blackleg nurseries sown on, or adjacent to, infested canola stubble from the previous season. Little is known about the genetic control of resistance, and the mechanisms responsible for generating pathogenic variability of L. maculans isolates in Australia is largely uncharacterised. Australian B. napus varieties are the most blackleg-resistant spring varieties in the world. Apart from growing blackleg-resistant varieties, other strategies that minimise infection and delay any breakdown in varietal resistance include growing canola on the same area only once every 3 years, destroying stubble, and eradicating volunteer plants between cropping seasons. Additionally, strategic use of chemicals can provide effective control to supplement varietal resistance in areas prone to severe blackleg infestation.

Seedling and adult plant studies were used to identify the race structure of Leptosphaeria maculans (the cause of blackleg) on oilseed Brassica species in Australia. Host-pathogen interactions using a set of 12 differential host lines identified 14 seedling relationship, however, between seedling and adult plant reactions to individual isolates, indicating that seedling and adult plant resistance are under different genetic control. While non-specific adult plant resistance was observed in the B. napus line Jet Neuf, host-pathogen interactions confirmed the existence of race-specific adult plant resistances in other differential lines.

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Control of take‐all (Gaeumannomyces graminis var. tritici) of wheat, with fungicides applied at seeding, was investigated at three naturally infested field sites. Fungicides were applied with seed either as granules or as pellets at rates ranging from 1‐5 to 140 kg a.i./ha. Treatment with benzimidazole and triazole fungicides resulted in lower disease severity on seminal roots, up to 100% fewer deadheads and more than 200% greater yields.

The effect of flutriafol, applied at sowing as fungicide coated superphosphate, on the severity of blackleg disease of rapeseed was studied in the field. Fungicide rates from 50 to 200 g a.i./ha reduced disease severity and markedly increased yields. With blackleg resistant cultivars, economic yield responses were achieved even when disease severity was low.