Good weed management includes correct identification, appropriate cultural practices, avoidance of introduction and chemical use
G
Managing WEEDS!
ood weed management includes correct identification, appropriate cultural practices to minimise
problems, avoidance of weed introduction and, finally, chemical use if required. Turfgrass professionals throughout the world have encompassed the reduction in availability of chemical control agents for both weeds and other problems in turfgrass management and, in my opinion, the number and range of available compounds for weed control will continue to decline in future years, forcing turfgrass managers to seriously consider other options in the fight against weeds.
Cultural Practices
Cultural management of weeds in turfgrass includes the use of mowing, fertilisation, cultivation, irrigation, and selection to impact upon weed populations. It is easy to forget that promoting a vigorous, healthy sward is critically important in controlling weed numbers. Having a good management programme in place, including correct nutrition, irrigation and aeration, will not only increase
the health of the sward but will also promote the sward's cover and limit the possibilities of weed growth. Good nutrition helps to maintain turfgrass density and vigour. By increasing the turf stands cover, light will be prevented from reaching the soil surface which will, in turn, delay the germination of seeds in the spring due to the cooling effect of the turf canopy on the soil surface. Inadequate fertilisation, in particular nitrogen, leads to an open sward that is more susceptible to weed infestation and may also weaken the sward, reducing disease and stress tolerance levels. However, excessive nitrogen applications can lead to succulent soft growth which, in time, can cause grass death and allows weeds to grow. It is also important to remember that excessive quantities of phosphorus in the soil, particularly near the surface, can encourage development of germinating weed seeds.
The goal of every turfgrass manager is to have strong healthy grass and this is also achieved through using the correct mowing height. Turfgrass mowed too short will become open, often with a poorly
developed
rooting system, which will encourage weed and disease invasion. Mowing recommendations include frequent mowing at the tallest height specified for the specific turf and particular situation. This practice, as well as helping the plant to carry out its physiological process, will also reduce available light levels to the soil surface. Proper mowing height is critical to maintaining turf density. In general, mowing below the optimum height will increase invasion of weedy grasses. Over-watered turf often grows very
rapidly, allowing turfgrass plants with shallow and weak root systems to develop, subsequently allowing weeds and diseases to readily invade. On the other hand, under-irrigation causes open turf stands, and grasses can go dormant, allowing weeds to flourish. Once weeds are established, they can often grow well in drought environments since many have exceptionally deep roots. Activities such as aerification, vertical mowing and slitting are methods of reducing thatch and soil compaction. Compaction reduces the amount of pore spaces in the soil, which may favour the growth of certain weeds such as knotweed since it can tolerate lower levels of oxygen in the soil. Shade can also favour weed growth, since it reduces light quantity and quality leading to turfgrass stands with reduced density. Tree pruning and in extreme situations tree removal may be required.
Biological weed control
Recently, the concept of using
biological control agents as a
weed
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