K-O Weeds

Control of Common Weeds

Weeds are indexed alphabetically.  Select the section of interest.



Knotweed, Prostrate (Polygonum aviculare L.)
Repeat applications of dicamba or two- or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA.  Other suggested options include atrazine/simazine, metribuzin, triclopyr alone or combined with clopyralid or 2,4-D. Oxadiazon may provide good PRE control if applied at or before the time for crabgrass control.

Kyllinga spp.
Annual kyllinga species can be controlled with Basagran, Image, Manage, Certainty, Monument or repeat applications of MSMA or DSMA.  Perennial species require repeat applications of Image, Image + MSMA, Certainty, Monument or Manage.

Lawn Burweed or Spurweed (Soliva pterosperma)
Preemergence or postemergence applications of simazine or atrazine in mid-fall provide excellent control.  Prompt and Sencor also work well in tolerant turfgrasses.  Repeat applications of two- or three-way broadleaf herbicide mixtures, Velocity, Manor/Blade, or Monument also provide control.  Key to control is applications in fall when weeds are small.

Mat Lippia or Matchweed (Phyla nodiflora)
Products containing atrazine or simazine applied twice 30 days apart.  Prompt (a pre-mix of atrazine and Basagran) also works well.  Products containing two- or three-way broadleaf herbicide mixtures applied at least twice 7 days apart also work in tolerant turfgrasses.

Byrum argentum has a silvery appearance, is referred to as silvery thread moss, and is found frequently on greens. Moss are threadlike, branched, primitive nonvascular plant forms encompassing many species. They are not parasitic and they spread by spores disseminated by wind and water movement.  Mosses are able to photosynthesize and fix nitrogen.  Moss is most noticeable on close-cut areas such as tees and putting greens that are poorly drained (thus remain continuously wet) and heavily shaded.   Moss can survive weather extremes in a dormant state or by living symbiotically with blue-green algae. Algae, therefore, can be a precursor to moss encroachment and should be discouraged to prevent moss colonization.  Moss mats typically development in summer following periods of rainy, overcast, warm days. 

Cultural Controls: Control involves a long-term, persistent program combining cultural and chemical control methods realizing healthy turf is the only means to cure and prevent moss occurrence. Control begins by correcting those conditions which predispose the turf to moss growth. This involves reducing surface moisture by improving air circulation and light exposure by removing adjacent underbrush and selectively removing trees. Improve surface and subsurface drainage and reduce irrigation frequency and amount. Reduce freely available nitrogen at the site. Reduce irrigation and improve growth of the turfgrass where the moss is present so the turf can form a dense area. If the area occupied by moss is large, spiking, verticutting, and topdressing will help to break-up and dry the mat. Moss turning orange-brown or golden brown in color indicates positive desiccation is occurring. 

Several trends in fertility and moss development have been noted. For example, calcium-rich soil may encourage certain moss species while moss tends to be discouraged in potassium adequate soils. Ammonium sulfate at 1/10 to 1/8 lbs N/1,000 sq.ft. applied weekly is thought to help desiccate moss and encourage competitive turf growth. Use only when air temperature are below 80F and adequate moisture is present. Applying ground limestone (75 to 100 lbs/1,000 sq.ft.), baking soda (6 oz/gal water to drench), hydrogen peroxide, or hydrated lime (2 to 3 lbs/1000 sq.ft. in 3 gallons of water) will help desiccate the moss and raise the soil pH level which favors competitive turf growth. Diluted bleach and dishwashing detergent, chloride, ferrous sulfate at 4 to 7 oz/1,000 sq.ft., granular iron sulfate at up to 3 lbs/1,000 sq.ft., or ferrous ammonium sulfate at 10 oz/1,000 sq.ft. also may help reduce moss growth. However, these should not be used on greens during hot temperatures, as they may cause varying levels of turf discoloration. Increase the mowing height as low mowing aggravates the problem. Spike or rake the dehydrated moss layer to remove any remaining impervious layer. 

Chemical Controls: Chemical control is erratic and often unsuccessful, especially if agronomic practices are not corrected which favor moss growth and development.  Quicksilver 1.9 L at 2.1 to 6.7 oz/acre has provided good moss control.  Treat wher air temperatures are <85F and use at 100 GPA and repeat in 2 to 3 weeks.  Products containing potassium salts of fatty acids (e.g., DeMoss) applied weekly at 2 to 3 oz/1,000 sq.ft. or formaldehyde control moss through a contact mode-of-action but should be carefully used and all label information followed closely. Chlorothalonil may be used but only during summer. Chlorothalonil (4 oz/1000 sq.ft. for Daconil Weather Stik, 6 oz/1,000 sq.ft. Daconil Zn) should be applied every 7 days for 3 consecutive weeks in 5 gal water per 1,000 sq.ft. Air temperatures should be above 80F (preferably, >85 F) at the time of application for success. Being nonvascular plants, high gallonage is needed for complete coverage. 

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