Toolbox for Vegetation Control




What is This Treatment?

Herbicides are chemicals designed to control vegeration. Contact herbicides destroy the portions of plants on which they are sprayed. Pre-emergent herbicides are applied to the soil to stop vegetation before it even starts. These may be selective or nonselective. Translocating or systemic herbicides function by absorption hrough the foliage or root system of plants. These circulate through the plant leading to its demise.

When to Use This Treatment?

Contact herbicides may be used to control existing weeds within landscaped areas where a chemical soil treatment might not be desirable. They may be used to “knock down” or kill top growth on perennial plants, but the root system of perennials is not destroyed by single applications of contact sprays. Contact herbicides may be used to control vegetation where a future roadside planting is anticipated since they leave no serious toxic residue. They may also be used for edging ground covers.

Pre-emergent herbicides are best applied when there is soil moisture present, and require irrigation or rainfall soon after application to activate the herbicide and/or move it to the soil profile. Selective preemergent herbicides are useful for landscape and roadside applications. Higher rates of these soil acting (pre-emergent) herbicides are used chiefly where no vegetative cover is desired. Fire prevention strips, under guardrails, signs, and delineators are examples ofwhere non-selective herbicides would be used.

Translocating herbicides are generally used to control perennial weeds, shrubs, and trees that may not be adequately controlled with other types of herbicides due to their extensive root systems.




For further information contact a Licensed Agricultural Pest Control Advisor or your district maintenance landscape specialist.


Herbicide were once widely adopted but has recently been criticized for its adverse environmental and health effects. In 1992, Caltrans decided that in order to reduce the impact of harmful side effects they must reduce herbicide usage by 80% in the year 2012. By the year 2000 a 50% reduction had been achieved.

"What is This Treatment?" and "When to Use This Treatment?" is taken in part or in whole from the Caltrans Maintenance Manual Volume 1 Chapter C2.