The answer to 'weed control yellowing' is that the yellowing of weeds is often a sign that a weed control treatment is working. When weeds are sprayed with an herbicide, the chemical disrupts the weeds' ability to produce chlorophyll, causing them to turn yellow and die off. This is a common and expected outcome when using effective weed control products.
The yellowing is a clear indicator that the herbicide is penetrating the weed and doing its job. However, if the weeds do not eventually die and brown out completely, it may be a sign that the treatment was not strong enough or that the weeds have developed resistance. In that case, you may need to try a different herbicide or consult a professional landscaper for more effective weed control solutions.