Dallisgrass – Public Enemy #1

Dallisgrass (Paspalum dilatatum) is a warm-season perennial bunch grass that was introduced to the United States from South America in the 1800s. It is now considered a troublesome weed in the transition zone, particularly in bentgrass golf courses. It is commonly found in wet areas such as drainage ditches, low spots, and heavily irrigated turfgrass. Dallisgrass has a faster growth rate than most turfgrasses and can adapt to low mowing heights, making it difficult to manage in golf courses, sports fields, parks, and home landscapes where a uniform surface is necessary. It produces distinctive seedheads that are easy to identify, and its rhizomes can spread and establish new clumps. Dallisgrass is also competitive for nutrients and water in ornamental landscapes.

Management of dallisgrass in bentgrass golf courses involves preventing establishment of new plants through cultural and physical control practices. This includes adjusting irrigation and fertilization practices, planting competitive plants, changing mowing height or frequency, and physically digging out young plants before they form rhizomes or set seed. Mowing alone is not effective in removing dallisgrass. It is important to maintain dense turfgrass through proper irrigation, fertilization, and mowing practices to resist dallisgrass invasion. If established dallisgrass plants are present, they can be carefully dug out, and mulch can be applied to prevent new germination and seedling establishment. Preemergence herbicides can also be used to control germinating dallisgrass seed. However, herbicides may take multiple applications over a period of 2-3 years for adequate control.

For bentgrass golf courses, there are very limited options for postemergence herbicides to control dallisgrass. There are no selective herbicides available for dallisgrass control in bentgrass, ryegrass, or creeping fescue. MSMA can be used to suppress the dallisgrass but in order to completely control the species it will require multiple applications that can stress the sensitive bentgrass, it also has restricted use on golf courses. Glyphosate is a nonselective postemergence herbicide that can be used as a spot treatment for dallisgrass, but it will also damage desirable turfgrass and may require reseeding of bare areas. Managing dallisgrass infestations in turfgrass, including bentgrass golf courses, is a challenging process that may take several years, and complete renovation may be necessary in heavily infested areas.

Kenmure Country Club
Agronomic Plan for Dallisgrass Control

1. Identification and Monitoring: Train the course maintenance staff to identify dallisgrass and regularly monitor the fairways for any signs of infestation. Early detection is crucial for effective management.

2. Cultural Practices:

a. Mowing: Maintain proper mowing practices for Creeping Bentgrass, including regular and consistent mowing at the appropriate height to promote dense turf growth and minimize bare areas where dallisgrass can invade.

b. Irrigation: Implement proper irrigation practices to avoid over-watering or under-watering, as both can weaken the turf and create favorable conditions for dallisgrass growth. Water deeply and infrequently and avoid watering during hot summer months when possible.

c. Fertilization: Follow a balanced fertilization program based on soil test results to promote healthy turf growth and competition against dallisgrass.

d. Aeration: Regularly aerate the fairways to alleviate soil compaction and improve water and nutrient penetration, which can help promote healthy turfgrass growth and reduce dallisgrass competition.

e. Thatch Management: Manage thatch buildup through regular dethatching practices to prevent accumulation of organic matter that can create a favorable environment for dallisgrass growth.

f. Seeding: Consider overseeding fairways with Creeping Bentgrass to promote dense turfgrass growth and competition against dallisgrass. b. Traffic Management: Implement traffic management practices to minimize stress on the fairways and avoid creating bare areas where dallisgrass can establish.

3. Physical Removal:

a. Hand Pulling: For isolated or small patches of dallisgrass, hand pulling may be effective. Make sure to remove the entire plant, including the roots, to prevent regrowth. This method is most effective when done in the early stages of infestation and should be followed by proper disposal of the removed plant material to prevent spreading.

b. Sod Replacement: For larger areas of dallisgrass infestation, sod replacement can be considered. Remove the affected turfgrass along with the underlying soil and replace it with new sod or plugs of Creeping Bentgrass. Proper care, including watering and fertilization, should be provided to promote establishment of the new turfgrass and prevent dallisgrass re-infestation.

4. Herbicide Management:

a. Preemergence Herbicides: Apply preemergence herbicides labeled for use on Creeping Bentgrass fairways in early spring and fall to prevent the emergence of dallisgrass seedlings.

b. Postemergence Herbicides: Use selective postemergence herbicides labeled for use on Creeping Bentgrass to control dallisgrass in fairways. Herbicides such as MSMA may be effective in controlling dallisgrass. Follow label instructions carefully and apply during the appropriate temperature and growth stage of the dallisgrass.

5. Regular Monitoring and Follow-up: Continuously monitor the fairways for any signs of dallisgrass regrowth or new infestations and promptly implement appropriate management strategies as needed.

It's important to note that effective dallisgrass management may take time and consistent efforts.