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* HOME * Fine leaf Fescues * Coarse leaf Fescues * Weed suppressiveness * Additional Information * Acknowledgements
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Why are certain fescue weed suppressive? Over the last decade, the study of plant-plant interactions and utilization of allelopathy and plant interference as a potential weed management tool has received increasing attention. The use of allelopathy for weed management relies upon the species-specific responses of a target weed to chronic, and/or sublethal doses of an allelochemical (plant growth inhibitor), which can be exuded or leached from nearby living plants or decomposing residues. Weed suppressive cover crops that have been successfully used to suppress annual weeds have included economically important cereals such as wheat, oat, rye, barley, sorghum and rice. Although studies on allelopathic crops have focused on these key species, many other weedy and crop species show promise of allelopathic potential for suppression of surrounding vegetation, including several turfgrasses such as buffalo grass, perennial ryegrass, bermudagrass and both tall and fine fescues.
However, until now, few studies have been conducted to further evaluate the weed suppressive potential of these species. Our recent trials with weed suppressive ornamental groundcovers and turfgrasses for the New York State Department of Transportation have shown that the ability to establish rapidly, produce a dense turf or canopy thereby reducing light availability at the soil surface, and allelopathic properties can all influence weed suppressive ability. A review of the literature shows that Festuca spp. can be strongly weed suppressive when used for erosion control in agronomic, orchard and vineyard settings. Prior studies have focused on the weed suppressive effects of tall fescue which was shown to be potentially allelopathic by production of toxic root leachates.
In 1990, in studies in Kentucky, we demonstrated that creeping red fescue (F. rubra L. spp. rubra and ssp. tricolphylla) was highly weed suppressive when established as a living mulch or as killed sod in no-tillage field experiments. Recently, we have conducted a series of field studies in Ithaca, NY as well as in Riverhead NY, with Dr. Andy Senesac which show that certain cultivars of creeping red, chewings or hard fescue exhibit the ability to effectively suppress weeds over a multi-year period. An initial study was conducted in 1999-2002 as part of the National Turfgrass Evaluation Program (NTEP) to evaluate a collection of 78 fine leaf fescue cultivars for turfgrass quality, seedling vigor, and ability to suppress the establishment of common annual and perennial weeds. Using these criteria, Dr. Rossi evaluated the overall suitability of the cultivars for use in turfgrass settings, and we evaluated their potential to inhibit the establishment of common turf weeds, including large crabgrass, annual bluegrass, white clover and dandelion. Weed suppressive ability was visually evaluated, and several cultivars consistently produced dense stands of high quality turf and provided good to very good (greater than 70%) suppression of common turf weeds when established using the same planting density. Other cultivars provided moderate (between 35% - 70%) to (< 30%) little weed suppression.
Recently, with Dr. Frank Schroeder in the Department of Chemistry at Cornell University, we isolated and identified the main bioactive constituent in the inhibitory root exudates collected from the chewings fescue cv. Intrigue.This highly active inhibitor was identified as m-tyrosine, a simple derivative of p-tyrosine. M-Tyrosine was found in large quantities in root exudates of chewings fescue cultivars, strong red creeping cultivars and Arizona fescue. It suppressed weed seed germination and seedling growth in both soil and soilless assays, generally at concentrations of 100uM or less, which are in the range of application rates of several preemergent herbicides such as pendimethalin. Similarly, m-tyrosine exposure at low concentrations resulted in stunted root growth, reduced cell division and likely impacts cell elongation or cell wall formation in developing weed seedlings. The inhibitor is not highly selective in that it is active with every weed and crop species tested, but large crabgrass, barnyardgrass, dandelion, mustard, cress and other small-seeded weeds are highly sensitive to its presence. Currently, we are attempting to further identify its mode(s) of action, and determine, with industry support, its potential to be developed as a soil-applied natural herbicide. There may be additional related or unrelated inhibitors present in
the root exudates of both fine and coarse fescues. At this point, we are
evaluating other chemical constituents of fescue root exudates for biological
activity. |
