The life cycle of weeds should be monitored for the most effective eradication

Now that spring is in full bloom, it’s time to gain control of the weed population in pastures.

Annual weeds, both broadleaf and grass weeds, can lead to serious problems for both pastures and forages. Proper weed management this time of year is crucial. Weeds can be a tricky problem because there are many different definitions of a weed. The same plant may be considered a weed in one setting and may be beneficial in another. Ultimately, a weed is a plant that is growing where it is not wanted.

The first step in proper weed management is knowing your enemy. Identifying weeds can be a very difficult task. Many of them look similar but they do not all have the same mode of action. Weeds have different life cycles and growth habits, because of this, there is no one-size-fits-all solution to managing the weed population. However, if you don’t know what you’re going after, it’s going to be difficult to be successful.

Weeds are easiest to control early in their life stage. Most weeds can be controlled best when they are less than 4 inches in height and diameter. Taking time to walk through pastures and focus on weed population will save a lot of time and money in the long run. It is not uncommon for the same weed species to show up in a field year after year, so it’s important to recognize weeds early. If you have newly acquired land or are in the process of acquiring land, perform a thorough walk through and consider what kind of investment you are going to have to make in the soil to have adequate conditions for pasture or crop management.

Many management techniques require specific weed life cycle details to aid in developing a control strategy. Thus after you have identified the weed you are dealing with, you need to determine what part of its life cycle or what stage of growth the weed is in. Depending on this additional information, a mode of action can be decided upon. Once the plant goes to seed, many of the modes of action will not be as effective. For this reason, it is important to limit the amount of seed that weeds produce.

“Mowing, grazing or spraying weeds during flowering, or slightly before, will help to limit seed production,” Sarah Kenyon, University of Missouri Extension agronomy specialist, said.

Another important consideration would be soil fertility.

“Healthy, productive soil will develop better forage,” said Kenyon. “Productive forage will do a better job at competing with the weeds.”

In some circumstances mowing and grazing will not be effective and herbicide control will be most appropriate. Chemical control is most effective when applied to weeds that are again, less than 4 inches in height and diameter. When it comes to herbicide, it’s critical to know the growth stage because some weeds should be sprayed before flowering, while others can wait until after flowering.

“For example, the best time to spray thistle is when it is in the rosette stage, before it bolts (the stem shoots up and it flowers), if a herbicide application is made after flowering, the plant is still likely to produce viable seed,” University of Missouri Extension Agronomy Specialist Jill Scheidt said. If seed is produced, then the risk is significantly elevated for the weed to return again and again.


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