Dateline: August 4, 2005

Scientists study links between grass, allergies

DALLAS – “Have you ever driven down the road and seen someone mowing the lawn wearing a mask? This is an example of the relationship between allergies and mold spores in lawns.” Dr. Phil Colbaugh, research plant pathologist at the Texas Agricultural Experiment Station in Dallas, cites a common image seen in Texas throughout the warm weather months.

Colbaugh is studying the relationship between landscaping choices and practices, seasonal weather and potential exposure to allergenic mold spores. While his research will eventually include flowering plants, woody ornamentals, trees and herbs, Colbaugh is currently focusing on turfgrasses. His research results are being prepared for peer review, but have not yet been published.

The research began with a goal of determining whether different turfgrasses support different levels of allergenic mold spores. Emily Williams, research associate in plant pathology, said the initial study involved clippings from residential lawns in Richardson and Plano.

High school students participating in Colbaugh’s annual Summer Environmental Research Internship program spent eight weeks collecting turfgrass clippings from St. Augustine and Bermuda grass lawns in these two North Texas communities. Then they counted allergenic mold spores washed from the plant materials.

Sunny Bermuda grass locations had the highest mold spore counts, Williams said, and both sunny and shady Bermuda grass samples contained more spores than did the St. Augustine samples. The results also showed a large difference in lawns with full sun versus lawns with full shade. Both the sunny Bermuda grass lawns and the sunny St. Augustine lawns had three times more allergenic mold spores than shady lawns.

“Texas is a really bad area for asthma and allergy sufferers,” Colbaugh said. “The potential for exposure to allergens is high, and the exposure to mold spores is just one component in a complicated picture.”

Should grass clippings be left on a lawn or removed after mowing? The scientists advise leaving them.

“They are a great source of nutrients, including nitrogen, potassium and phosphorus, reducing the need for additional chemical fertilization,” Williams said. “They contribute organic matter to the soil over time. Bagging these materials for curbside garbage collection is costly, and it takes up limited landfill space. And there are ways to reduce the potential for spore numbers on established lawns.”

In recent related research, Colbaugh and Williams have shown that when a mulching blade was used, spore numbers were much lower than when a standard blade was used.

This summer the researchers are measuring the differences among a number of turfgrass types under test plot conditions. Those grasses include St. Augustine, Zoysia and Reveille Hybrid Bluegrass.