COLUMBUS, Ohio -- Incorporating compost into soils when lawns are seeded reduces the severity of leaf rust, a fungal disease that attacks perennial ryegrass.
Ohio State University plant pathologists found that the amount of leaf rust on perennial ryegrass was reduced by 50 percent when the turfgrass was seeded into soils with at least a one inch layer of composted sewage sludge. The study is the first of its kind to document the suppression of a foliar turf disease through the incorporation of compost into the soil.
Mike Boehm, one of the project researchers, said the nitrogen that the compost adds helps ward off the disease. "We know that some fungi, like leaf rust, like to attack turf that is growing under nutrient-stressed conditions," said Boehm. "The perennial ryegrass grew so well with the additional nitrogen that the pathogens were not able to attack it."
Perennial ryegrass was chosen for the study since it is most susceptible to leaf rust and is a common turfgrass seeded in Ohio. Leaf rust, caused by a pathogen of the Puccinia species, is recognized by a yellowing of turf blades, followed by reddish or orange-colored streaks on the leaves. The disease is most active under continuous warm days with dry conditions. Fungicide applications are currently the most effective means of controlling the disease.
Boehm said it is unclear whether the reduction in leaf rust was caused exclusively by the additional nitrogen or if there were other factors involved.
"The compost is packed with microorganisms that do have plant-enhancing characteristics," said Boehm. "The study didn't separate the microbiology of the compost from the nutrient impact of the compost - whether the induced-resistance is from organisms that changed the physiology of the plant to make it less susceptible or if the nitrogen was at work. My guess is it is a little of both."