Right-Of-Way Control Category 6 Practice Test

Timing is everything for herbicides. A preemergent herbicide is applied before weed seeds have germinated, often at planting or before the first weeds begin to emerge. It stays in the soil and forms a barrier that prevents seeds from germinating or from establishing once germination starts. It won’t affect weeds that are already growing, which is the domain of postemergent herbicides. The other terms describe how long the chemical remains active or how it works on plant tissue, not when it’s applied relative to weed emergence. So, the herbicide applied before the weeds emerge is preemergent.