|I have a broadleaf weed problem called|
|Dallisgrass is not a broadleaf weed so let's make sure we're talking about the same weed in your lawn. Dallisgrass is a warm season coarse perennial which is light green in color. The leaves are rolled in the bud, flat and wide (1/2"). Auricles are absent and the ligule is tall, pointed, and membranous. Dallisgrass has hairs on the lower portion of the leaf near the ligule.
The seedhead contains 3 - 6 spikes, with seeds on both sides of the spike. Dallisgrass can from short thick rhizomes, but spreads upright in clumps. This highly invasive plant germinates in soil temperatures of 60 to 65 degrees F and thrives in the hot humid conditions of the southern states.
If this describes the weed in your lawn, it is dallisgrass. If not, submit a new question to this forum and we'll see if we can't identify it for you.
In bermudagrass, dallisgrass is effectively controlled by two applications of MSMA or similar materials at 3 pounds per acre. Applications in early spring are most effective and should be repeated at 2-week intervals. MSMA should be applied with a boom or broadcast sprayer in 100 gallons or less of water per acre.
Make applications of MSMA 3 to 4 days after mowing to provide more leaf surface to absorb the herbicide. Do not water for at least 24 hours after treatment and delay mowing for several more days. Dallisgrass leaves will begin to show discoloration 3 to 5 days after treatment and significant leaf burning should be apparent after 7 to 10 days. Within 2 weeks some regrowth may occur and a second application of MSMA is necessary.
In St. Augustine and centipedegrass lawns, spot treatment of dallisgrass with glyphosate (Roundup) is most effective. Treated areas need to be plugged or sodded with St. Augustine or centipedegrass after dallisgrass dies to prevent other weeds from becoming established in the dead areas. Preemerge herbicides may also be helpful in St. Augustine or centipede turf to prevent the spread of dallisgrass from seed.