Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: http://read.dmtmag.com/i/67175
Landscape and Turf Maintenance Signs (right) and symptoms (left) of Pythiumblight. Photos courtesy of Lee Burpee turfgrass with prolonged periods of leaf wetness. Moss and algae are often signs of over-irrigation and applications should be reduced when present. Annual bluegrass is often a result of over-irrigation, particu- larly when coupled with over-fertilization. On the other hand, because warm sea- son grasses, such as bermudagrass, tolerate relatively high atmospheric temperatures and produce extremely deep rooting, less frequent irrigation can be tolerated. Deep and infrequent irrigation will promote deeper rooting, particularly when the sur- face is allowed to dry between irrigation. Allowing the surface to dry between irri- gation events will decrease the potential of disease associated with over-irrigation and prolonged periods of leaf wetness, but also increases the potential for development of drought stress. Therefore, those using the deep and infrequent irrigation regime should regularly monitor for drought stress and localized dry spot. Cultivation Turfgrass root growth can be maxi- mized and soil organic matter can be mini- mized with soil cultivation. Soil compaction causes reduced root growth, poor drainage and, ultimately, increases sus- ceptibility to disease and weed encroach- ment. Weeds associated with compacted soils include knotweed and goosegrass. Excessive organic matter accumulation can cause decreased drainage and rooting, and increased disease activity. The vast ma- jority of infectious turfgrass pathogens can survive on organic matter when the turf- grass is healthy, which increases the poten- tial for infection during periods of adverse environmental conditions. Cultivation practices that reduce organic matter accu- 22 Landscape and Irrigation May/June 2011 mulation include core cultivation and ver- tical mowing. Weed management Annual broadleaves (e.g. prostrate knotweed and spurge) can be controlled with burndown products like carfentra- zone because they lack the necessary root mass or carbohydrate reserves to reproduce the "burned" foliage (see Table). These her- bicides work very quickly and can be very useful on difficult-to-control weeds such as prostrate knotweed, which thrives in com- pacted soils. Annual grasses (e.g. crabgrass, gooseg- rass and foxtail) are most efficiently (low cost, highly effective) controlled with pre- emergence herbicides. However, the use of preemergence herbicides in cool season turf may not be an option if you are con- stantly interseeding to encourage full turf cover. With the loss of MSMA in turf, quinclorac has become a staple for poste- mergence crabgrass control, but it does not provide the same control on goosegrass. Annual bluegrass thrives in cool weather conditions (i.e. winter in the warm season zone, and spring and fall in the cool season and transition zones) and is a prolific seeder even at low mowing heights. For effective control of annual blue- grass, cool season turfgrass herbicides are usually applied in small doses and repeated at short intervals. Programs include more than one product type applied at differing portions of the growing season. For exam- ple, flurprimidol (a plant growth regulator) Table: Herbicides and their intended strategy of use for management of annual broadleaf and grassy weeds in cool season and warm season turfgrass, table developed by Aaron Hathaway. Cool season turf Annual broadleaves Annual grasses carfentrazone (burndown), isoxaben (preemergence) quinclorac for crab- grass, fenoxyprop for goosegrass (postemergence) Annual bluegrass ethofumesate, bispyribac sodium, mesotrione (postemergence) quinclorac (postemergence); numerous products (preemergence) pronamide, (preemergence); trifloxysulfuron- sodium, foramsulfuron (postemergence) paclobutrazol, flurprimidol (plant growth regulators) Caution: apply only when warm season turfs are growing vigorously; do not apply 6-8 weeks prior to or during field use as it will halt growth * Read labels for correct application program timings and rates www.landscapeirrigation.com Warm season turf carfentrazone (burndown) Strategy* Control before they produce and disseminate seed Apply postemergence early in growth stage if possible Be prepared for turfgrass and annual bluegrass injury