Phytophthora infestans, the oomycete responsible for potato late blight, has been a global challenge for potato crops, leading to annual losses of around 5%. The disease favors moderate weather conditions, often linked to La Nina events in Australia, and can lead to total crop failures if unmanaged. Despite its widespread presence, Australia has successfully prevented the entry of more aggressive strains, maintaining control over the disease through stringent biosecurity protocols.
In contrast, Europe and North America have experienced severe outbreaks, with the Netherlands facing its worst in 30 years during 2023. The emergence of a new aggressive strain and evolving fungicide resistance have compounded the issue. The disease's complexity is further highlighted by its two mating types, A1 and A2, with the latter being particularly concerning due to its ability to recombine and form oospores, enhancing disease survivability and resistance.
Australia's situation remains relatively stable, with only the A1 mating type detected, a strain that has not changed since the early 1900s. This stability allows for effective disease management through good farm hygiene, certified seed usage, resistant cultivars, and appropriate fungicide applications. The Australian strain remains sensitive to metalaxyl, unlike its counterparts in other regions.
Symptomatically, late blight manifests as pale-grey lesions on leaf margins, progressing rapidly and affecting tubers with a tannish-brown rot. The disease can also impact other solanaceous plants, acting as a disease reservoir. Monitoring for exotic, more aggressive strains is crucial, as they may present resistance to metalaxyl and thrive under different conditions.
If an exotic strain is suspected, immediate reporting to the Exotic Plant Pest Hotline is advised to safeguard Australia's potato industry from these more virulent threats.
Source: AusVEG