DALLAS -- "Have you ever driven down the road and seen someonemowing the lawn wearing a mask? This is an example of the relationshipbetween allergies and mold spores in lawns. Dr. Phil Colbaugh, researchplant pathologist at the Texas Agricultural Experiment Station inDallas, cites a common image seen in Texas throughout the warm weathermonths.
Colbaugh is studying the relationship between landscaping choicesand practices, seasonal weather and potential exposure to allergenicmold spores. While his research will eventually include floweringplants, woody ornamentals, trees and herbs, Colbaugh is currentlyfocusing on turfgrasses. His research results are being prepared forpeer review, but have not yet been published.
The research began with a goal of determining whether differentturfgrasses support different levels of allergenic mold spores. EmilyWilliams, research associate in plant pathology, said the initial studyinvolved clippings from residential lawns in Richardson and Plano.
High school students participating in Colbaugh's annual SummerEnvironmental Research Internship program spent eight weeks collectingturfgrass clippings from St. Augustine and Bermudagrass lawns in thesetwo North Texas communities. Then they counted allergenic mold sporeswashed from the plant materials.
Sunny Bermudagrass locations had the highest total mold sporecounts, Williams said, and both sunny and shady Bermudagrass samplescontained more spores than did the St. Augustine samples.
The results also showed a large difference in lawns with fullsun versus lawns with full shade. Both the sunny Bermudagrass lawns andthe sunny St. Augustine lawns had three times more allergenic moldspores than shady lawns.
"Texas is a really bad area for asthma and allergy sufferers,"Colbaugh said. "The potential for exposure to allergens is high, andthe exposure to mold spores is just one component in a complicatedpicture."
The Asthma and Allergy Foundation of America annually ranksallergy capitals. In 2004, Dallas / Fort Worth, Austin, Tulsa andOklahoma City all ranked within the Top 10 of 100 American allergycapitals.
Allergy is a genetic susceptibility to the IgE anti-body, whichis present within the body of an allergy sufferer. When IgE comes intocontact with inhaled allergens such as pollen and fungal spores,histamine and other compounds that produce an allergic reaction arereleased.
According to the National Institute of Allergy and InfectiousDiseases, more than 50 million Americans, or one in six, haveallergies. That makes allergies the sixth-leading cause of chronicdisease in the United States, costing $18 billion dollars annually.
Asthma, a constriction of the muscles lining the lungs isoften triggered by rapid allergic reactions and can become lifethreatening if not treated quickly and properly. Fungal spores, inparticular, pose a threat for people with asthma.
According to AsthmaNow.com, 9 million children and 14 millionadults have been diagnosed with asthma. The condition also leads tomore than 10 million missed school days each year and causes more than14.5 million missed work days, valued at $2 billion to $3 billionannually.
Sensitization, a heightened reaction to allergens, can becaused by repeated exposure to fungal spores during routine activities,such as mowing the lawn or playing on the grass. Therefore the type ofturfgrass may be a key factor in the allergic asthmatic reaction.
The most aggravating types of mold spores for asthma suffererscome from the fungal genus Alternaria, a member of the familyDematiaceae, which are recognized by their dark coloration, Williamssaid. Fungi reproduce by means of spores, microscopic structures thatcontain the main allergenic irritant. Dematiaceae and other types offungal spores dwell on dead vegetation, such as decomposing turfgrassclippings, and in the soil.
Fungi play a vital role in the environment as decomposers. Dr.Harriet Burge of Environmental Microbiology Laboratories Inc., said afungal-free environment is not possible or desirable. Fungi constitutean integral part of the environment, whether urban or rural.
"What was important to us was that we saw big differences inlawn types and spore counts," Colbaugh said. "Bermudagrass lawns werefound to support twice as many spores as St. Augustine grass. It meansthe type of grass you choose to put down for your lawn or your athleticfield may make a difference to those who suffer from allergies andasthma. St. Augustine supports fewer of the fungal spores that triggerallergic or asthmatic reactions."
Should grass clippings be left on a lawn or removed after mowing? Colbaugh and Williams advise leaving them.
"They are a great source of nutrients, including nitrogen,potassium and phosphorus, reducing the need for additional chemicalfertilization," Williams said. "They contribute organic matter to thesoil over time. Bagging these materials for curbside garbage collectionis costly, and it takes up limited landfill space. And there are waysto reduce the potential for spore numbers on established lawns."
In recent related research, Colbaugh and Williams have shownthat when a lawnmower with a mulching blade was used, spore numberswere much lower than when a standard blade was used.
Colbaugh and Williams emphasize they are not providing medicaladvice. Their goal is to provide science-based research in an area thatlacks information. Ultimately, they hope this research will helpeveryone make informed choices about lawns and sports turfs.
This summer the researchers are measuring the differencesamong a number of turfgrass types under test plot conditions. They aretracking maintenance items such as fertility, mowing height, mowingfrequency and irrigation, all of which affect the number of fungalspores within the turfgrass. They are also monitoring daily weatherpatterns to understand the influences of rain, dry weather, high winds,or high and low humidity.
"Preliminary results are confirming what we learned last yearabout Bermudagrass," Williams said. "Bermuda supports much highernumbers of allergenic mold spores than do the other types of grassestested."
Those include St. Augustine, Zoysia and Reveille HybridBluegrass, which was developed here at the Dallas center by Dr. JamesRead."
The next step in their research is to conduct air samplingduring and immediately after mowing events, to determine exposure riskto the mower, Williams said. They would also like to determine whetherthe number of spores within the turfgrass clippings affects the numberof spores in the air within the home landscape. No date has been setfor that research effort, due to the high cost of the samplingequipment needed to conduct the test.
Until they can perform these aerobiological tests, Colbaughand Williams plan to study other landscape materials, such as compostpiles and mulching materials.
This summer, interns have explored the abilities of inorganicand organic mulching materials to support the growth of Alternaria.
"Preliminary experiments have shown some organic mulchingmaterials do support fungal growth while others do not," Williams said."These are preliminary experiments and we look forward to furtheringthis research in an effort to provide even more information forclinicians and homeowners."
Materials provided by Texas A&M University - Agricultural Communications. Note: Content may be edited for style and length.
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