Webster's dictionary defines a weed as "a plant that is not valued where it is growing and is usually of vigorous growth; especially: one that tends to overgrow or choke out more desirable plants." This is especially true in pasture and hayfield situations. Weeds are plants that compete with desirable forages for sunlight, water, nutrients, and space, thereby reducing yield. Some weeds are lower in quality than forages grown. Some weeds can be toxic to animals or create feeding problems. Whatever the rationale for classifying a plant as a weed, it can usually be said that pasture and hayfields would be much more productive if weeds were eliminated.
Weed identification is the first step in weed control. In order to control a plant, you need to know what it is. Different types of plants respond differently to control methods. Weeds can be classified into annuals, bi-annuals, or perennials. They can further be classified by whether they are warm season or cool season and by genus and species. The more information you have on a particular weed, the better the odds of getting satisfactory control. There are a number of resources available on-line to help with identification, such as the Dow AgroSciences website (http:// www.dowagro.com/range/weed/). There are also a number of publications available through the Alabama Cooperative Extension System, such as "Weeds of Southern Turfgrass," that can be quite helpful in identifying weeds. Once you know what weed you are dealing with, then you can develop a weed control strategy.
Weed Control Strategies
Weed control strategies do not always revolve around chemical control. Management can solve many weed control issues. Healthy and vigorous stands of forages are the best weed control. While chemical control methods will sometimes be necessary to control weeds, good management plans must also be in place to prevent the reinfestation of the weeds into the pasture or hayfield. Good management practices such as soil sampling and maintaining fertility levels can do a lot for keeping weeds from becoming a problem.
Other management practices can help control weeds such as rotational grazing. Rotational grazing has positive effects on forage production and cattle handling. They include better utilization of forages, improved interaction animals, and controlling weeds. Rotational grazing allows animals to be moved from paddock to paddock (doesn't have to be a bunch of small paddocks), reducing the tendency of cattle to selectively graze certain spots on a farm. Rotational grazing prevents openings in forage stands that weeds can and will quickly invade.
Pulling weeds is another control strategy. Producers can pull up weeds at first notice and before weeds produce more seeds. This prevents weeds from becoming a problem.
There are times when chemical control of weeds is necessary. Numerous companies market several herbicides for weed control. No one chemical is "the best" for every situation. Most landgrant universities produce some type of information, chart or table that helps you to identify the best herbicide for your situation. These Integrated Pest Management Guides (IPM) help you determine the proper herbicide for weed control.
IPM guides for Alabama can be downloaded from The Alabama Cooperative Extension System website (www aces.edu), or picked up from your local extension office.
After properly identifying weeds and choosing the right herbicide, knowing when to apply the herbicide is key to successful control. As a general rule, winter annuals should be controlled from November through March and summer annuals controlled from April to mid July. Timing of control for some of the harder to control perennials is largely dependant on the plant's growth stage. For example, blackberry and dewberry are perennials that should be controlled after the fruit has matured and new growth has begun. If you are uncertain about application timing for a particular weed, contact your local extension agent.
Other Considerations for Successful Weed Control
Numerous other things need to be considered before chemical application. One is to apply the herbicide at the correct rate. Consulting the label, weeds should be sprayed using the lowest rate with an accurately calibrated sprayer. Be aware of the danger of drift of chemical. Never spray on a windy day. You should be aware of the danger of harming desirable plants with herbicides. If you plan to establish legumes, such as clovers, be mindful that most range and pastureland herbicides can be detrimental to legumes and some can have residual effects that last for months. Always read and follow the labeled instructions for a herbicide.
There are a lot of variables to consider and decisions to be made before you load the sprayer and start out across the pasture. Do your homework and use your resources. If you would like more information about weed control, please contact your local Extension office or Regional Extension Agent.