WSU Extension

Hortsense

Herbicide Damage : Long-term residual herbicides
(revision date: 5/1/2013)


Biology
Uracils, substituted ureas and other long-term residual herbicides are used to obtain total vegetation control usually for long periods of time. These products are persistent in the soil for one or more growing seasons and are taken up by plant roots. Damage occurs when the material is applied over the root zone of nontarget plants. An upward spiral pattern of healthy foliage may appear on some conifers. Some long-term residuals may cause veinal chlorosis (yellowing of veins and adjacent tissues), particularly the uracils and substituted ureas which are photosynthesis inhibitors. However, they rarely cause marginal or interveinal necrosis, which instead may be caused by triazine herbicide injury.
Management Options

Non-Chemical Management
  • Avoid applications where root uptake can occur on neighboring desirable plants.
  • Carefully read all label instructions and precautions prior to purchasing and applying these herbicides.
Select non-chemical management options as your first choice!

Chemical Management

Carefully read all label instructions prior to using long-term residual herbicides.

Images
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Caption: Long-term residual herbicide damage
Photo by: R. Maleike
Caption: Rose veinal chlorosis
Photo by: R. Maleike
Caption: Long-term residual herbicide damage in an upward spiral pattern
Photo by: R. Maleike