Increasing Herbicide Efficiency
- 5 hours ago
- 3 min read
As we get into the growing season many of us will likely need to use herbicides to help us reach some of our wildlife habitat goals. Using herbicides efficiently means less chemical usage which is good for a number of reasons; better for the environment, less money out of our pockets and more time to work on other projects.
As with all chemical applications it as has been stated by numerous folks over the years... "The label is the law!" If you are applying a herbicide in a manner which is not approved on the label you are responsible for the negative effects of that application. Calibration of spray equipment with prevent you from over or under applying the amount of chemical necessary to achieve control of your targeted weed species. There are two common goals with herbicide application, complete burndown of all vegetation on a site and selective control of certain weed species. Understanding your objectives and which chemicals can safely and effectively help you reach those objectives is an important first step. In certain circumstances you may be looking to clean up existing weeds prior to planting a crop or other vegetation. In that case you need to know what the replant interval is for the chemical you are using on the crop you intend to plant. Some chemicals have a replant time wait interval of basically zero while others the replant interval maybe months!
When to apply your herbicide is just as important what herbicide to apply. Here in the Midwest the weather in Spring is often pretty volatile, extremes in temperature and possibly more importantly wind speed. Most folks can logically conclude that very windy days are not ideal or even safe for herbicide applications. Best case scenario your herbicide drifts off the area you are trying to apply it to, and you get poor weed control, worst case scenario the herbicide drifts onto vegetation you were not intending to spray and you kill desirable vegetation. More so if your herbicide damages a neighbor's crops or property!! Many folks tend to choose early morning or late evening to spray as wind speeds are often less at those times. Scientific herbicide studies clearly indicate that spraying in the morning first thing is the least effective time of day for the targeted plants to absorb the herbicide. Those same studies indicate that herbicide uptake is most effective after 9:00 am and before midnight. During that time of the day the plants are actively growing. Keep in mind that drought stressed plants are far less susceptible to herbicide uptake. Drought stressed plants, especially broadleaf weeds can roll their leaves or wilt, decreasing the surface area available for herbicide contact. The waxy cuticle layer on the leaf is likely to increase during times of drought which also inhibits the adsorption of herbicide. Hot (over 90 degrees), windy, low humidity days can cause the herbicide to evaporate more quickly as well, before it has a chance to be adsorbed by the plant and also increases the risk of herbicide drift.
Surfactant is often an overlooked part of obtaining good results from herbicide application. Surfactant allows the herbicide to "stick" to certain plants better and overall keeps the herbicide in an active state in contact with a plant longer, increasing the uptake of the herbicide. Some herbicides come with surfactant as part of the formulation; others will specifically call for the addition of it when applying to certain weeds or at certain times. Use surfactant when it is called for! Your targeted weeds size is also an important consideration. Most herbicide labels will indicate what size weeds are most susceptible. Annual weeds tend to be most susceptible when they are young plants less than a few inches tall. Besides surfactant you may need a water conditioning agent prior to adding your herbicide. Some herbicides bind to positive charge mineral ions in hard water, rendering them ineffective at being adsorbed by the weeds. If the water you are applying your herbicide with is high in dissolved minerals (hard water) the addition of AMS or Citric Acid will help prevent the herbicide from binding to the minerals in the water and make it more effective. Also keep in mind, especially if you are spraying more mature weeds or weeds that have become resistant to certain herbicides that you should use the maximum rate allowed by the label. Using the maximum rate will help to insure you get good control of your weed species on the first application and help to prevent herbicide resistant weeds.