Rust disease is a major concern for farmers of sugarcane worldwide. Rust is caused by a fungus that attacks the leaves of sugarcane plants, resulting in reduced yields and poor sugar quality. The characteristic orange-brown pustules of rust disease are visible on the foliage and stems of infected plants. Managing rust disease in sugarcane requires a combination of cultural, chemical, biological, organic, and natural control strategies.
These include the selection of varieties resistant to rust, proper irrigation and drainage, removing and destroying infected plant material, and applying fungicides. Biological control methods employ naturally occurring microorganisms to combat the rust fungus. In contrast, chemical control involves the use of synthetic fungicides. Natural control methods include predators and beneficial insects.
Organic control methods employ natural products and cultural practices to regulate rust disease. Effective rust management in sugarcane requires an integrated strategy incorporating multiple control methods, routine monitoring, and prompt intervention. Sugarcane growers can minimize the impact of rust disease and ensure healthy, productive crops by employing the appropriate management techniques.
Rust Management in Sugarcane
The Causal Organisms of Rust Disease
Puccinia erianthi is the pathogen that causes Rust Disease in sugarcane. The disease can be identified by its reddish-brown, elongated uredinia with hyaline to light brown paraphyses. The thick-walled, orange-brown, obovoid urediniospores have an echinulate surface with four to five equatorial pores. The teliospores measure 30-43 x 17-23 m and are dark brown, clavate, two-celled, and slightly constricted at the septum.
The Disease Cycle of Rust Disease
Rust Disease in sugarcane starts its life cycle with the germination of urediniospores, which are disseminated by wind and rain splash. The spores then cause the characteristic orange-brown pustules on the host plant. Additional urediniospores are produced and then released within these pustules to continue the cycle. Later-season teliospores are overwintering structures, enabling the disease to persist into the next growing season.
Causes/Conditions Favorable for Rust Disease in The Field
Rust Disease in sugarcane is caused by the fungus Puccinia kuehnii, which is spread by microscopic and resilient spores readily dispersed by wind and water splash and can survive in plant residues in the soil. The disease flourishes in warm, wet, and humid conditions during summer and early autumn, typically infecting canes older than six months. The optimal growth and transmission of the disease occur between 20 and 30 degrees Celsius and 70 to 90 percent relative humidity. High wind speed and prolonged cloudiness may aggravate the disease.
Symptoms of Rust Disease
- Early symptoms consist of tiny yellow patches on both leaf surfaces.
- Lesions transform into orange-brown patches up to 4 mm in length and 3 mm in width, typically near the leaf base.
- orange spores created on the underside of leaves
- Severe infection causes crop canopy reduction and the appearance of brown patches on the leaf sheath.
- Lesions enlarge and change color from red-brown to brown.
- A band of pale yellow-green develops around lesions.
- Severe infection causes numerous brown or rust-colored lesions on individual leaves.
- The aggregation of lesions into large, irregular necrotic areas can lead to premature mortality of the leaf.
- A severe infection can substantially reduce a plant’s number of living leaves.
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