For most of us, disease prevention is a no brainer. Whether it’s getting a vaccine to prevent a serious disease or taking medicine that helps the body prevent illnesses, prevention is preferred to having to deal with illness.
Can the same logic be applied to preventative weed control?
In a perfect world, crop production managers would have systems in place to prevent weeds from invading their crop production fields.
Well, it turns out that preventing weeds from emerging from the soil is a common practice. Crop producers can apply herbicides to the soil prior to weed emergence in an effort to stop some species from emerging. This form of weed control, often referred to as preemergence control, is widely adopted by producers, and will thwart some but not all weeds. Postemergence herbicide application targets those weeds that escape preemergence herbicide applications.
How about preventing weeds from entering your crop production fields, is that even possible you wonder?
Weed infestations begin with the arrival of invasive plants. Recognizing and preventing the spread of invasive plants is the ultimate goal of any preventative weed control program.
What are invasive plants?
- Invasive plants are a class of plants that can enter a habitat, quickly become established, and change the nature of the habitat. The invasive plants appear to sneak into the habitat and may go unnoticed for a while as they establish themselves and later become problematic plants in their new habitat.
- If nothing is done to get rid of them, the invasive plants may become the dominant species within the habitat with an ability to spread into new areas.
- While stopping the spread of established invasive species is a priority for many land managers, it isn’t easy to identify which species is invasive and has the potential to spread and cause serious damage to the environment, our health, our economy, etc.
What is preventative weed control?
The most challenging part of a weed control program is preventing weeds from infesting an area. This is often not an easy undertaking. The difficulty is identifying a potential weed prior to its invading an area. Potential weeds start out as invasive plants and when they become established within a habitat they are normally referred to as weeds.
Why is preventative weed control difficult?
A case can be made for managing weeds after they have infested an area; there will be support for these measures. However, when dealing with potential threats, support is not always forthcoming. Furthermore, it is easy to measure if control was successful when you have a weed infestation as opposed to when you don’t.
Effective preventative weed control techniques can help reduce the prevalence of weeds. In turn, lowering the potential for yield loss and the need for managing weeds within the crops will likely improve economic returns.
Preventative weed control tactics
Here are some tactics that can prevent weeds from occurring in a field.
- Preventing seed production by annual weeds–ensuring weeds do not go to seed helps prevent the replenishment of the soil seedbank. Preventing weed seed production can be accomplished by controlling weeds when crops are growing using preemergence and post emergence herbicide applications. When needed, late-season broadcast or spot spray herbicide applications are required.
- Preventing vegetative spread by perennials – similar to annual weeds, vegetative propagules that can be produced by perennial plants can be prevented from becoming established either chemically or manually. Late season treatment with herbicide is often the best way to target this group of weeds.
- Using clean crop seed that is free of weed seed – planting certified seed helps prevent the inadvertent introduction of weeds into the field you are planting. Certified crop seed comes with a guarantee of very low possibility of introducing weeds to your crop field.
- Cleaning farming equipment between fields and farms – weed infestations can happen when you use farming equipment between fields. Soil or plant debris from a weedy field can be transferred in this manner. Cleaning the farm equipment prior to use can help prevent the inadvertent introduction of weeds.
- Scouting for new weeds – routinely scouting fields to identify new species invasions before they become established in a field.
- Small patch treatment to prevent the expansion of patches into large infestations – commonly referred to as spot treating, this tactic prevents weeds from expanding their range within a field and beyond.
- Education about weeds– knowing how to identify weeds is key to identifying weedy and invasive plants which is the first step in weed management.
- Isolating imported animals for several days –animals may inadvertently be carriers of weed seeds on their bodies or within their digestive tracts. Seeds of some species can pass through animal digestive tracts intact and be ready to germinate when they are excreted. During isolation, the animals can be inspected for seeds and their excrement disposed of in a way that would minimize inadvertent introductions of new weed species.
- Purchasing only clean hay (to prevent importation of weeds or weed seeds in animal feed) – buying hay from producers who are able to certify that their fields were relatively free of weeds minimizes the potential of introducing new weeds.
Preventative weed control regulations
The first step of and good weed management program is the purchase and planting of clean seed. The United States government regulates the transport and sale of seeds via the Federal Seed Act. The law requires that crop seed be labeled to indicate the percentage of weed seed present, including noxious weeds.
Noxious weeds are plants that are especially undesirable, troublesome, and difficult to control. The Noxious Weed Control Act and the Federal Plant Protection Act help limitthe spread of noxious weeds.
Preventing a weed invasion should be the first line of defense for all weed control programs.
Zimdahl, R.L. 2007. Fundamentals of Weed Science – 3rd Ed. Academic Press – Elsevier Inc. Pp. 259-326.
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