Weed/Grass Control Around Stationary Objects
Stationary objects such as guardrails and sign posts must remain clear of unsightly vegetation in order to serve their purpose. Pre-emergence and post-emergence herbicide treatments may be utilized to prevent weeds and brush from growing around these structures. When planning such a program, care should be taken to select herbicide materials that will not cause complete bare-ground conditions which could lead to erosion control problems. This planning is especially needed in areas of increased drainage. The Department is currently encouraging the establishment of low growing turf such as centipede under guardrails, to reduce erosion and weed growth. Centipede's allelopathic effect should reduce the need for future herbicide applications.
Weed/Grass Control Along Paved Shoulders
- Pre-emergence control
Asphalt and concrete roadway surfaces often have weed growth which can deteriorate pavement rapidly. Pre-emergence weed/grass control beneath pavement is often used to prevent the initial growth of undesirable vegetation upward through a new pavement. In this type of application a non-selective soil sterilant herbicide material is applied to the base soil surface prior to the asphalt paving process. The objective is for the herbicide to act as a "barrier" to prevent the vegetative growth. In most cases the herbicide material must be applied immediately prior to the laying of the asphalt material, in order to avoid potential off-target damage via run-off.
- Post-emergence control
If undesired vegetation has already grown through or upon the paved surfaces, the only practical alternative is post-emergence control. Various non-selective herbicides can be used for this application, but care should be taken to choose stable materials that will not cause undesired residual effects, such as damage
from drainage run-off.
Weed/Grass Control on Capped Traffic Islands
The concepts and herbicide materials for vegetation control on capped traffic islands is basically the same as for paved shoulders, as described above. Limited work has been done to include appropriate non-selective herbicides mixed with liquid asphalt in crack-sealing operations on capped traffic islands, as a vegetation control method. The user of this method must ensure that the herbicide material is compatible with the liquid asphalt.
Weed Control in Ornamental Landscape Plantings
Good cultural practices such as mulching can significantly reduce unwanted weed growth and conserve moisture in formal roadside ornamental plantings. Experience has shown that weed management in these plantings is not practical without the use of herbicides. Pre-emergence herbicide applications may be made in the fall for control of winter weeds and grasses and during the spring to control summer weeds and grasses. Post-emergence herbicide applications may be applied throughout the year to control undesirable vegetation that has emerged during the growing season.
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