dithiopyr

Dithiopyr is a synthetic herbicide used to control weeds in turfgrass and some ornamental crops. It is marketed in formulations such as Dimension and other brand products and is valued for its dual preemergence and early postemergence activity, particularly against annual grasses like crabgrass and some goosegrass, as well as certain broadleaf weeds.

Mode of action and characteristics. Dithiopyr inhibits weed growth by disrupting cell division in susceptible plants, affecting the development of shoots in young seedlings. Its soil activity creates a preventative barrier that reduces weed emergence, while it can also provide early postemergence control on small, actively growing weed shoots. The herbicide tends to be selective for many common turfgrasses when used according to label directions, though sensitive ornamentals and some species outside target crops can be injured if misapplied.

Application and use. Dithiopyr is typically applied to established turf either before weed emergence (preemergence) or on very young weeds (early postemergence), depending on the product label. Timely irrigation after application and adherence to recommended rates are important for effectiveness and to minimize injury to desirable plants. It is widely used on lawns, golf courses, sod farms, and some nursery settings to protect turf from annual grasses and certain weeds.

Environmental and safety considerations. Dithiopyr has moderate acute toxicity in humans with exposure, and environmental concerns focus on potential effects on aquatic organisms and non-target plant species. It can persist in soil for varying lengths of time depending on conditions, with degradation influenced by soil characteristics, moisture, and light. Proper handling, storage, and adherence to label directions are required to reduce risks.

Regulatory status. Dithiopyr is registered for use in many regions with crop- and site-specific label requirements. Regulatory status, permitted crops, and application restrictions vary by country and jurisdiction.