The degree of wintergrass control achieved will be influenced primarily by the rate and frequency at which SHORTstop 200SC is used. Most temperate research shows that a ‘little and often’ application strategy is the most effective means of suppressing wintergrass competition in a bentgrass greens (see your tech rep for more info).
The Turf Growth Regulator (TGR) ingredient in SHORTstop is root absorbed and needs to be watered in to take effect. After irrigation, SHORTstop binds to organic carbon and therefore settles at the very top layer of soil, where wintergrass roots congregate due to their shallow habit. Because bentgrass and other cool season grasses (when healthy) produce deeper rooting, they display less sensitivity to the TGR active ingredient in SHORTstop.
By maintaining sufficient levels of this unique TGR in the surface of the root zone during cool season growth, wintergrass will be inhibited while other cool season grasses grow unaffected. SHORTstop is therefore a tool to shift the competitive dynamics of a cool season sward in favour of other more desirable cool season species, such as bentgrass, ryegrass or fescue. Cultural practices, climate, soil type, turfgrass variety and wintergrass biotype also play a part in the degree of control achieved when using SHORTstop 200SC. A coordinate program that combines nutritional, cultural and mechanical aspects of turf maintenance will enhance the degree of control achieved.
After application of SHORTstop 200SC the growth and competitive ability of wintergrass will be reduced within 1-2 weeks. The degree of discolouration and growth reduction is directly related to the rate used. Very low rates can be used on a pure Poa annua surface to achieve turf density and seed head control, while heavier applications will discolour wintergrass severely.