Calibration, rate, timing

These are important topics to discuss, because all factors are important in getting the best weed control.

Calibration is important in order to make sure that the spray equipment you are using is putting out the right amount of chemical and is not putting in on too light or too heavy.

If your sprayer is not putting out enough chemical, you will not get very good control, and in fact can cause herbicide resistance where the plants targeted actually become resistant to the chemical and require more to control them, or even completely nullify the chemical to where it won’t work anymore.

If your sprayer is putting out too much chemical, then you are over applying which wastes chemical and money, is unsafe for the environment, and is also against the law.

Rate is similar to calibration and is important for the same reasons. You want to make sure you are mixing the chemical at the correct rate to get the best control and not over apply.

Timing is important because weeds have a timeline that herbicides will work in. If you spray outside this window of opportunity then you may not get the best control, or in some cases, will not get control at all. The biggest thing to be aware of is that if you spray too late, such as when the plants have seeded out, the herbicide will not be taken into the plants because they are getting ready to die or go dormant until next year.

Many people think that if you use more chemical you will get better control. This is not the case because a few things can happen when you over apply. The most common would be that the extra chemical is not needed. The other thing that can happen is that if you wet the plants down too much and actually soak them, a lot of the chemical can drip off of the plants instead of getting into them and controlling the weeds.

Another thing that can happen is that when over applying, the plants may look dead but really only the tops of the plants have been controlled. This happens because the plants stop taking in the herbicide which doesn’t get down to the roots. If the plant is a perennial, for example, the roots are still intact and will come back next year.

So, as you can see, all of these factors are very important and must be followed to get the best control, not waste chemical and money, and be safer for the environment.

Contact our office at (509) 754-2011 Ext 4710 with any questions, or visit our website at www.grantcountyweedboard.org.