Consider the following factors carefully before choosing a control material. Each factor may affect the success of your brush control program.

Suberization. Plants use this natural healing process to prevent insects or diseases from infesting tissues after cuts or wounds occur. Woody plants develop a layer of protective, corky cells over the damaged tissue. Suberization can reduce herbicide effectiveness by preventing absorption. When you use the hack and squirt or cut stump method of application, apply the herbicides immediately to achieve maximum absorption. Delaying application of water soluble herbicides for as little as one hour can reduce absorption and subsequent control.

Root grafts. Sometimes the roots of different plants share vascular tissue through grafting. Root grafting occurs primarily within the same species but may occur between plants of the same genus. A herbicide can move from a treated tree to an untreated desirable tree, killing or injuring it. Damage to desirable trees as a result of root grafting may occur from the use of 2,4-D, Banvel, Roundup, Ally, Escort, Grazon, Garlon, and Remedy.

Flashback. This term describes the passive loss of a herbicide from the roots of treated trees. Once the herbicide is released from one tree, it is available for uptake from another. This means that a treated tree may release herbicide back into the environment, injuring other nearby trees and vegetation. Flashback damage can occur with Grazon, Banvel, and occasionally 2,4-D.

Formulations. The herbicide formulation may affect its performance characteristics. Match the formulation and application method. For example, water soluble amine formulations of 2,4-D and Garlon are preferred for hack and squirt applications. For basal bark applications, use oil soluble ester formulations such as Pathfinder, Crossbow, or Remedy. Other herbicide formulations include wettable powder, dry flowable, water dispersible granules, or flowables. Formulations applied in the dry form include pellets and granules.

Ditchbank brush control. Herbicide use on ditchbanks is a problem since most water passing through the ditches will, at some point, be used for irrigation or drinking. Some of the most effective brush herbicides such as Spike, Arsenal, and Velpar have warning statements on the label stating that the product should not be applied to ditches used to transport irrigation or drinking water. Rodeo (5 lb/gal glyphosate) is the best option since it has the fewest restrictions related to water use.

Standing dead brush. Herbicide-killed trees eventually decay, but this may take several years. Options to avoid standing dead brush are (1) cut the brush with an ax or chain saw and then treat the stumps to prevent sprouting, or (2) treat the brush and then cut when the brush is dead. With most herbicides, the brush can be safely burned as firewood. While mechanical brush control is usually more expensive, time consuming, erosion prone, and less likely to achieve root kill, it does avoid the problems of standing dead brush and handling and applying herbicides.