Rust
Tranzschelia discolor
What is Peach rust (Tranzschelia discolor)?
Peach rust is a fungal disease caused by Tranzschelia discolor. It affects plants in the Prunus genus, including peaches, nectarine, almonds, plum, apricot, and cherry. The disease spreads through airborne spores, which require moisture for infection. Symptoms include yellow chlorotic spots on leaves, rust-colored spores on leaf undersides, water-soaked lesions on stems, and small brownish spots with green halos on fruit. Severe infections can lead to premature defoliation and reduced yields.
How does Peach rust (Tranzschelia discolor) occur?
The disease cycle involves multiple spore stages, including urediniospores, teliospores, basidiospores, and aeciospores. Moisture from precipitation or irrigation splashes spores onto nearby leaves, initiating infection. In subtropical regions, urediniospores overwinter in twig cankers and pustules under the leaves, serving as primary inoculum for the next growing season. The disease can also involve a sexual cycle, where infected leaves produce teliospores that overwinter and produce basidiospores capable of infecting alternate hosts.
Symptoms
1 - Plant Effects
• Severe infections lead to premature leaf drop, reducing photosynthesis and weakening the plant. • Infected plants experience decreased fruit production and lower crop yields. • Lesions on fruit affect quality, making them susceptible to decay and secondary infections.
2 - Soil Effects
• Reduced plant vitality impacts nutrient cycling and availability in the soil. Altered soil microbial communities and interactions due to changes in plant health and the presence of pathogens.
3 - Environmental Impact
Severe infections disrupt the ecosystem, affecting diversity and interactions among organisms in the orchard environment.
Solutions
1 - Cultural Practices
• Allow adequate air circulation to promote the drying of leaves and reduce disease spread. • Maintain a good canopy structure to improve air movement and sunlight penetration. • Choose resistant or tolerant peach and other cultivars to reduce susceptibility to peach rust.
2 - Monitoring and Management
• Implement monitoring programs to detect the disease early and take appropriate action. • Manage irrigation to minimize leaf wetness and reduce disease-friendly conditions. • Remove and destroy infected plant material to reduce inoculum sources.
3 - Applications of Fungicides
• Copper-based fungicides (e.g., Bordeaux mixture) • Sterol-inhibiting fungicides (FRAC Code 3) • Quinone outside inhibitor (QoI) fungicides (FRAC Group 11) • Succinate dehydrogenase inhibitors (SDHI) fungicides (FRAC Group 7) • Apply fungicides according to recommended schedules and timings.
