Weed management

Introduction

Weed control practices in forests are designed to favour the growth of the desired tree species, improve visibility along forest roads, control noxious weeds, and improve wildlife habitats. The goal is to manage timber species, ground vegetation, and wildlife so that each component is maximized yet balanced. Vegetation management is a primary means to achieve a productive forest. Managers need to integrate the best cultural, mechanical, and chemical practices into appropriate and cost effective management systems to minimize losses and detrimental effects due to weeds.

Objectives of forest weed management

A forester might undertake a weed management program with one or more of the following objectives in mind:

Removing unwanted vegetation from planting sites to favor the planted trees. Releasing more desirable species from less desirable overtopping species.Thinning excess plants from a stand. Preventing disease movement through root grafts. Preventing invasion of herbaceous and/or woody vegetation into recreational areas and wildlife openings. Controlling vegetation along forest roads and around buildings and facilities. Eliminating poisonous plants from recreational areas. Controlling production-limiting weeds in a seed orchard or tree nursery. When establishing a forest, relatively few seeds or seedlings are introduced into an environment in which an almost unlimited number of other plants exist or have the potential to become established. The immediate goal of the forest manager is species survival, which is achieved by reducing the competition from weeds. Site preparation and tree release are the procedures that minimize the density and reduce the vigor of the competing vegetation in the year of and in the years immediately after planting. The type and intensity of management practices depend on the vigor of the desired (planted) species and the indigenous species.

Integrated control

Successful vegetation management plans incorporate the right package of practices into well planned programs that are executed on a timely basis. No single plan is best suited for each site, so careful analysis of each site is necessary. Routinely review the results obtained and modify the plans as needed to ensure satisfactory control.

Cultural control

Cultural weed control is simply carrying out those practices that favor the desired tree species and make them more competitive with weeds. Examples include the following:

1. Select the best adapted species and varieties.
2. Practice thorough site preparation.
3. Plant vigorous, large, healthy seedlings.
4. Plant seedlings at the appropriate spacing and replace those that die.
5. Apply necessary insect, disease, and rodent control measures.
6. Maintain optimum stocking levels for the site at each stage of stand development.

Mechanical control

Many specialized machines and attachments are used in forest vegetation management, including brush rakes, angle blades, shearing blades, rolling brush cutters, and shredders. Large offset disks and integral plows are sometimes used. In addition, chain saws, axes, brush hooks, powered brush cutters, hatchets, and other hand tools can be used in weeding operations. On gentle slopes, mechanical means of site preparation and rehabilitation are generally sufficient to remove debris, control weeds, prepare seedbeds, reduce soil compaction caused by logging, and carry out minor land leveling operations.

Mechanical thinning is sometimes practiced, especially in very dense stands where clearing in regularly spaced strips is desired and no selection of individual trees is necessary. Mechanical thinning is not acceptable for release when desired small trees are hidden by taller, brushy trees or where individual tree selection is desired.Mechanical control is not suited to all sites. The major obstacles to the use of mechanical vegetation management are unsuitable terrain, the likelihood of soil erosion, and relatively high operating costs. Manual vegetation removal can be done in areas inaccessible to machines or to complement or replace the use of large equipment. Manual cutting is most effective when species to be cut are not too dense and do not resprout. Because conifers do not resprout, they are easily controlled by cutting. Many brush species, however, resprout readily from the trunk or established roots, and this reduces the effectiveness of cutting. Manual cutting may not always be appropriate for site preparation or release, but it can be effectively combined with herbicide treatment of stumps to remove selected trees and prevent regrowth.

Chemical control

Chemical control of weed species is normally practical only once or twice in the life of a forest stand. The benefits of herbicides applied during site preparation and release may be evident through the life of the stand if their use is supplemented by all the other principles of good forest management. Use of herbicides is only one step in a long-term production plan. Application of herbicides must be both necessary and compatible with all other phases of the plan.Once the weed species to be controlled have been identified, the correct herbicide, formulation, rate, water volume, method of application, and time of treatment must be determined. Before using any pesticide, read the entire label.

Evaluation of results

After using any vegetation management practice, inspect the area to evaluate the results. Keep in mind the type and species of vegetation treated, the soil type, and weather conditions during and after application. Know the objectives of the control program when evaluating the results. In some cases, suppression of treated vegetation is sufficient; in others, selective control is desired. Initial herbicide activity and possible injury to adjacent desirable vegetation can be determined 2 to 4 weeks after application. The results of vegetation control treatments should be evaluated after about 2 months, at the end of the season, and then for several years. The effectiveness of brush and perennial weed control measures cannot be fully evaluated for at least 12 and sometimes 24 months after treatment.Evaluation must be an on-going activity. It allows you to make adjustments in rates, products, and timing of herbicide applications, and to plan any additional control measures that may be needed.

Source : FOREST PEST MANAGEMENT