Rust
Puccinia spp.
What is Rust (Puccinia spp) ?
Rust diseases are fungal infections that affect turfgrasses, caused by fungi in the Puccinia genus. They can be found on various types of grassy areas like golf courses, athletic fields, and home lawns. Symptoms include pale-yellow spots on leaves or stems that grow parallel to leaf veins. Over time, reddish-brown pustules form, releasing orange spores. Rust diseases usually appear in late summer or early fall, mainly affecting cool season grasses like perennial ryegrass and Kentucky bluegrass.
How does Rust (Puccinia spp) occur?
Rust diseases have a complex life cycle with different spore stages. The fungi produce windborne spores called urediniospores, which infect the host plant through tiny openings called stomata. Moisture, like heavy dew, is needed for spore germination and infection. Once inside the plant, the infection and spore production persist as long as the leaf lives. Rust fungi may need different host plants, including turfgrasses, shrubs, or ornamental plants, to complete their life cycle.
Symptoms
1 - Effects On plants
• Rust can cause reduced crop yield by damaging leaves, stems, and fruits. Severe infections weaken plants, making them more susceptible to other diseases, pests, and environmental stressors. • Additionally, infected plants may undergo defoliation, leading to decreased photosynthesis and energy production.
3 - Impacts on Environment and Soil
• Rust spores can be carried by wind or water, facilitating the spread of the disease to new areas. This can significantly impact ecosystems, affecting both cultivated and wild plants and potentially disrupting ecological balance. • Additionally, infected plant debris left behind can accumulate on the soil surface, leading to increased levels of organic matter.
Solutions
1 - Preventions
• Maintain adequate nitrogen and irrigation to promote healthy turf growth. • Avoid excessive thatch buildup and improve air circulation by regular aerating and dethatching. • Provide sufficient spacing between plants to promote air circulation, reducing humidity levels and creating less favorable conditions for rust development. • Remove and dispose of infected plant debris to reduce the source of inoculum. • Select rust-resistant turfgrass cultivars whenever possible.
2 - Application of fungicides
In cases of persistent rust problems, targeted application of fungicides may be necessary. • Triazoles: Tebuconazole, Propiconazole, and Metconazole • Strobilurins: Azoxystrobin, Pyraclostrobin • Copper-based fungicides: Copper sulfate, Copper hydroxide Mancozeb (Bonide® Orchard Spray) • Dithiocarbamates: Maneb, Mancozeb These are commonly used fungicides to prevent this disease. However, using these agents carefully and according to label instructions is vital to avoid unintended negative impacts on other organisms in the ecosystem.
