Postemergence applications are used primarily for the
control of broadleaf weeds and perennial grass weeds, but
they also can be used for annual grassy weeds if a preemergence
herbicide was not used or failed to control the weeds.
Postemergence weed control is most effective when the
weeds are young and actively growing, and when the soil is
moist and the temperature is warm. The grass should be
healthy and actively growing except when applications are
made to weeds in dormant turf.
Postemergence chemicals are applied to the foliage of
growing weeds. Avoid mowing for 2 to 3 days before and
after applying so there is more weed foliage to absorb the
chemical and translocate it to the roots. Apply the product
when rain is not expected for 24 hours after application. Also
avoid watering for 24 hours after applications.
Do not apply postemergence chemicals to turfgrass while
it is under heat or drought stress. Water the turf thoroughly
prior to application. Most postemergence chemicals should
not be applied when the temperature exceeds 85 to 90°F
during and after application.