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🇦🇺 Australia /Health & Science

Cotton growers race to treat leaf disease after mysterious arrival

From ABC Australia · () English

Summarized and contextualized by DistantNews.

At a glance

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  • A new and aggressive cotton disease, Ramularia leaf spot, has mysteriously appeared in northern Australia, causing significant crop damage.
  • Growers have limited treatment options as no chemicals are registered for the disease in Australia, with early planting being the primary strategy.
  • Industry groups are urgently seeking access to chemical treatments and developing a control strategy to prevent further spread and resistance.

Cotton growers in northern Australia are racing against time to combat a newly arrived and aggressive fungal disease, Ramularia leaf spot, which is wreaking havoc on crops. The disease, known by several names including areolate mildew and grey mildew, thrives in hot, humid, and wet tropical conditions, leading to outbreaks.

It's also called areolate mildew, grey mildew, or false mildew, because it looks like a mildew, but it's not a mildew

— Linda SmithDr. Smith explained the various names and nature of the Ramularia leaf spot disease.

Linda Smith, principal plant pathologist at the Queensland Department of Primary Industries, stated that treatment options are scarce. "It's a fungal disease that loves hot, humid, wet tropical conditions, and when you get these conditions you get disease outbreak," she explained. The disease, more common in the southeastern United States and Brazil, has caused significant yield loss and reduced fiber quality overseas. Its detection in Queensland, with evidence of defoliation, has raised serious concerns.

It's a fungal disease that loves hot, humid, wet tropical conditions, and when you get these conditions you get disease outbreak

— Linda SmithDr. Smith described the environmental conditions that favor the spread of the disease.

Growers face a critical challenge as no chemical treatments are currently registered for Ramularia leaf spot in Australia. Simon Struss, an agronomist in the Callide-Dawson region, reported that "every farm, every field showed symptoms of the disease." The primary strategy for growers is to plant their crops early, before the disease typically takes hold. After harvest, farmers are urged to bury infected crops to kill volunteer cotton and avoid consecutive plantings.

Overseas, it has been causing some significant yield loss … it can reduce both the yield and the fibre quality

— Linda SmithDr. Smith highlighted the economic impact of the disease observed in other countries.

Industry bodies are actively working to find solutions. "The race is on for Australia to access a chemical treatment," Dr. Smith said. Efforts are underway to secure permits for fungicides, aiming to develop a control strategy that employs multiple modes of action. This approach is crucial to reduce the development of fungal resistance and provide growers with viable choices. The industry is learning from past experiences, particularly regarding resistance management, to ensure a sustainable approach to combating this new threat.

With the detection now in Queensland and some evidence of defoliation of the crops, we're really concerned about it

— Linda SmithDr. Smith expressed concern over the disease's presence and impact on crops in Queensland.
DistantNews Editorial

Originally published by ABC Australia. Summarized and contextualized by our editorial team with added local perspective. Read our editorial standards.

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