What is Dithiopyr?
Dithiopyr is the active ingredient found in the popular herbibcide Dimension, among others. As an herbicide it is considered preemergent meaning that it is only effective if applied before the target weeds emerge. One of the common uses of dithiopyr is to prevent crabgrass from popping up in the spring.
How does Dithiopyr work? (Mode of Action)
Dithiopyr controls weeds by disrupting microtubules which are neccessary for plant growth, so essentially the target weeds are not able lto grow. It is important to make the distinction that pre-emerent herbicides do not destroy weeds entirely but rather prevent growth. That is why they must be applied annually to retain the desired effects.