CRABGRASS: There are about 200 species of crabgrasses native to tropical and warm temperate regions. “Crabgrass typically have spreading stems with wide, flat leaf blades that lie on the ground with the tips pointing upward or outward,” says L.B. (Bert) McCarty, Clemson professor of turfgrass science. “Crabgrass seed has a long germination period, requiring light for optimum germination, germinating in early spring when soil temperatures at four inches depth are 53 to 55 degrees Fahrenheit for 24 continuous hours.” Crabgrass often invades weak, thin turf where light can reach the soil surface where seed are located. They also germinate earlier on south facing slopes and adjacent to sidewalks and driveways.
“Preventively, a number of preemergence herbicides can be applied,” he says. “The key is to apply just prior to germination in your particular area and repeat applications 60 to 75 days after the initial. Post-emergence herbicides are highly dependent on the tolerance to the particular turfgrass species present.”
Many preemergent products control crabgrass, such as bensulide, dithiopyr, prodiamine, and pendimethalin. PBI-Gordon has preemergent herbicides to control crabgrass and other grassy weeds; Bensumec 4LF and Tupersan are sprayable, and Pre-San Granular 12.5G is granular, says PBI-Gordon product manager Jim Goodrich. Postemergent, there are several crabgrass-control products, including Q4 Plus Turf Herbicide, which offers effective control, as well as a broad-spectrum broadleaf weed control.
Nutsedge: Nutsedges are similar to grasses with long, linear shaped leaves. Nutsedge leaves, however, are arranged in threes and a cross section of the stem is triangular. Leaves are also covered with a very distinguishable (shiny) waxy cuticle.
Yellow nutsedge is a perennial, but their shoots die down in winter, McCarty says. Nutsedges are tolerant of wet conditions, so regulate soil moisture by using prudent watering practices and providing drainage.”
Preemergence control is available, but being a perennial these products must be applied prior to tuber sprouting, which is hard to determine since the shoots die down in winter but the plant is still alive. Postemergent herbicides should be applied prior to June 21, when tuber production is initiated.
PBI-Gordon products that contain the active ingredient sulfentrazone in different concentrations work to suppress it, like Surge Broadleaf Herbicide for Turf and TZone SE Broadleaf Herbicide for Tough Weeds. Q4 Plus, which has a higher load of sulfentrazone, controls yellow nutsedge. Katana Turf Herbicide eradicates yellow nutsedge from warm-season turf.
Clover: Clover leaves divide into three leaflets. White clover is the most widespread in the U.S. It’s a low-growing, perennial initially used as a companion crop in pastures due to its ability to fix its own nitrogen. White clover leaves often have a white, angled band partly encircling the base of each leaflet.
“Clovers typically invade low-maintenance turf sites that are insufficiently fertilized with nitrogen,”McCarty says. “Providing sufficient fertilizer discourages this invasion. Being mostly perennial, control is often with postemergent herbicides.”
Increase fertilization and raise mowing heights to reduce clover pressure on your golf course. Curatively, many products control clover, but they can require multiple applications, as clover can grow over itself and reduce the amount of product reaching the lower portions of the plant. PBI-Gordon has several products for the post-emergent control of clover; SpeedZone Turf Herbicide is a sound choice for clover control, as well as Q4 Plus, and TZone SE.
Chickweed: The most encountered chickweeds on golf courses are common and mouse-ear. Common is a mat-forming winter annual. Leaves are opposite, shiny, without hairs. Mouse-ear is a perennial, roots at nodes, and leaves are gray green and hairy. Flowers for both have five notched white petals, occurring in spring.
Postemergent chickweed control should take place in the fall into early winter before seeds are produced for subsequent generations and/or additional spread. Control is mostly with postemergent three- or four-way herbicides. As weeds mature, two applications seven days apart will be needed.” Always read and follow label directions.