TechNotes Nov. 20 - Rust, Leaf Removal, Soil Temperatures

Recovering from Rust

Rust caused by the pathogen Puccina graminis continues to be evident in many cool season lawns throughout the northern United States. Slow growth and drier conditions enhance this disease. Rust is especially severe on drought stress perennial ryegrass because it actually enhances water loss (ruptures the epidermis, leading to increased water loss). Perennial ryegrass infected with rust appears yellowish to orange in color. Closer observations of the leaf blades reveals the brownish-orange colored pustules on the leaf.

If dry conditions persist and temperatures warm, relieving dry soil conditions should be attempted to reduce the severity of rust. Late season fertilization will help promote the recovery of rust infected lawns.  Nitrogen applied once turfgrass growth has ceased but the turf is still green will help make for a healthy lawn going into the winter season.     

Leaf Removal is Beneficial

Fall leaf removal is not only necessary from an aesthetic perspective but also from an agronomic perspective. Although turfgrass growth slows or ceases this time of the year, the plant will continue to photosynthesize as long as the turf is green. Energy in the form of carbohydrates captured and stored from photosynthesis will go to enhance root growth and accumulate in the storage compartments (nodes, crowns, etc) to be used the following year.

Shading occurs when the leaves are left on the turf reducing the turf plants ability to photosynthesize. Thus, the full potential to capture sunlight is greatly diminished when leaves are left on the turf. Additionally, if the leaves get wet a microclimate under these leaves that promote disease development. The primary diseases that are favored by this environment are Microdochium patch (also known as pink snow mold or fusarium patch) and powdery mildew. Thus, blowing or raking those leaves off the turf is an important fall agronomic practice.

Soil Temperature Map