Actively growing weeds are much more susceptible to the herbicide. Many perennial weeds are best controlled in the early fall when nutrients are being stored in the root system. Diquat, Paraquat, and Sharpshooter kill foliage on contact and have no residual soil activity. They will suppress many species of annual grasses and some broadleaf weeds. Repeated applications may be needed to weaken and suppress perennial weeds.
Complete coverage is essential.
They can be applied over the top of a broadleaf crop when grasses are actively growing and before they reach maximum size. When applied to a labeled cut flower crop all open flowers should be harvested before application to avoid injury. Preemergence selective herbicides To prevent seedling weeds from emerging in a crop, a preplant incorporated or a preemergence chemical can be used. In selecting a preplant or preemergence chemical, care should be taken to select the herbicide that is labeled for a specific crop. This herbicide must be watered in after application to move the chemical into the germination zone of the weed seeds.