Field Paspalum

Biology

Field paspalum (Paspalum laeve Michx.) is a warm-season perennial weed with short rhizomes similar to dallisgrass (Paspalum dilatatum Poir.). Much of the below Weed of the Month entry comes from research conducted in Indiana on how to control Field Paspalum.This perennial weed is a wide-bladed warm-season perennial turfgrass that becomes easily visible in mid-summer. Additionally it can have either dark green or yellow green foliage. It is found in cool-season and warm-season turf. It has a short rhizomes near the soil surface but spreads primarily by seed.

Identification

It can be distinguished from one another by a few characteristics although they are more similar than different. The range of adaptation is different distributed into farther north than dallisgrass. Field paspalum can be found in Kansas, Missouri, Illinois, Indiana, Ohio, Pennsylvania, and Maryland whereas dallisgrass is less commonly distributed in those areas. Leaf sheath, leaf blades, and rhizomes of the two species are similar. Both species have terminal panicles with racemosely arranged branches of similar number and length. Dallisgrass can be distinguished from field paspalum by the spikelets in pairs appearing to be in four rows on dallisgrass compared to two in field paspalum. Additionally, dallisgrass has long, silky hairs on the spikelets while field paspalum is glabrous. Dallisgrass also has a 5- or 7-veined glume while field paspalum has a 3-nerved upper glume with veins at the margins.

Cultural control

Reduce soil compaction and promote practices that increase turf density. The most effective way to control these weeds is to dig up the clumps in the turf with a shovel.

Biological control

None known.

Chemical control

Spot treating with the nonselective herbicide glyphosate (found in products like Roundup) is another effective method against weeds. Glyphosate requires at least two applications: the first when the plant greens in spring (late April or May), and a second upon regrowth. Additional applications might be necessary. Dallisgrass and field paspalum can also be sprayed in October, before they change color for winter dormancy, using a 1-2% glyphosate solution (1.3-2.6 fl oz per gallon of water).

Be cautious with glyphosate, as it will kill desirable grass, potentially leaving brown spots. To minimize damage, apply glyphosate directly to the weeds, avoiding the turf. Tools like paintbrushes, sponges, or foam applicators are helpful for precise application.

In lawns with Kentucky bluegrass, fine fescue, tall fescue, or perennial ryegrass, applying mesotrione (Tenacity) at 5 oz/A with a two-week interval between three applications, starting in June, can reduce dallisgrass and field paspalum by over 75%. For tall fescue, two applications of fluazifop (Fusilade II) at 5-6 oz/A, spaced three to four weeks apart starting in late-April and September, can suppress these weeds. Enhancing fluazifop with triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A improves safety for the turfgrass. Avoid using on tall fescue seedlings less than four weeks old.

Tribute TOTAL (thiencarbazone + foramsulfuron + halosulfuron) at 3.2 oz/A is also effective on dallisgrass in bermudagrass and zoysiagrass. Apply multiple times in late summer and early fall before winter dormancy, followed by a spring application.

In zoysiagrass, two summer applications of fluazifop (Fusilade II) at 3-4 oz/A, three to four weeks apart, will suppress field paspalum and dallisgrass. Adding triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A to fluazifop enhances turfgrass safety.