Advertise in Print | Subscriptions
Published May 20, 2013, 10:21 AM

Keep weeds in check

Weed resistance to chemicals will continually increase. It only takes one weed to survive a treatment for it to pass on the genetic makeup to do so to the offspring. This creates more resistant weeds until there is a whole population of resistant weeds. Applying more herbicide will make these weeds even more resistant. This will happen over again even if the chemical formula for the herbicide is altered.

By: Kristine Larson, Agweek

Russian thistle or tumbleweed was first reported in the United States in 1877. It was documented in South Dakota and thought to have been brought over in flax seed from Ukraine.

It is now 2013, and despite massive efforts to get rid of this noxious weed, it has spread to almost every state in the nation, including Hawaii. This is just one example of the continuous battle against unwanted plant species.

I have heard a lot of talk in the last year about herbicides no longer being effective in controlling weeds. This is a natural occurrence of survival of the fittest and the answer is not to apply more herbicide. Weed suppression will exist when diversity is put back into a system because weeds emerge only where there is opportunity to do so.

Weed resistance to chemicals will continually increase. It only takes one weed to survive a treatment for it to pass on the genetic makeup to do so to the offspring. This creates more resistant weeds until there is a whole population of resistant weeds. Applying more herbicide will make these weeds even more resistant. This will happen over again even if the chemical formula for the herbicide is altered. It is only a matter of time.

Unwanted species never will be eradicated, so maybe the focus should be shifted to keeping them in check. Continuous cover helps suppression of weeds by competing for the same resources. Some species of plants have a natural component in their root systems that prevent other plants from growing around them. These are known as allelopathic plants. Dead or dying herbaceous cover helps block out sunlight while also using up soil space to prevent new, unwanted species. Diversity enhances the function of weed suppression.

Nature’s reset button

There is a natural succession that occurs after any type of disturbance, whether it is fire, a volcano or tilling. The area is void of vegetation, so the first plants usually to establish are called annuals. These plants complete their life cycle in one year. Many of our weeds are annuals, producing mass amounts of seeds to disperse as soon as possible. The next year, if left untouched, the area will contain mostly forbs, although grasses still can be found. Eventually, the area will begin to reach an equilibrium that contains a mix of forbs and perennial grasses, which are grasses that take more than one year to complete their life cycles.

When tillage occurs, it is as if the reset button gets pushed on this area. Weeds have the opportunity to grow and reproduce, making it harder for other plant species to establish. Continuous cover, rich in diversity, allows the system to function similar to how it did in its natural system.

Editor’s Note: Larson is the watershed coordinator for the Grand Forks County, (N.D.) Soil Conservation District.

Tags: