Herbicide Application Planning

By Jamie Breuninger


There is a lot of pressure on lawn care operators (LCOs) this time of year. Their window of opportunity is narrow, and they want to get to all of their customers before the weather warms and the phone starts ringing with weed complaints. Spring is the most popular time to make herbicide applications, but proper planning can give LCOs more flexibility and additional time throughout the year.

Turf managers can use their annual lawn service program as a guide to predict what weeds will appear when, and the different products that are needed to control or prevent them. When is the right time to use a three-way herbicide? When would products with amines or esters work better? Is a broadcast application needed in the fall, or would a spot treatment do the trick? Planning ensures that these and other questions are answered ahead of time. That way, LCOs have the necessary products available during the appropriate times, allowing them to address their customers’ concerns year-round.

Post control at preemergence timing

The timing of the first application of the season is critical. For effective preemergence control, an LCO needs to make that first application before weeds begin to germinate. For example, in the northern U.S., the first applications can begin in March after winter weather subsides. Ideal timing for first applications of fertilizer with a crabgrass preventer is when soil temperatures hit 50 F. So while an LCO is racing to get the first applications made to provide his or her customers’ lawns with a quick green-up and crabgrass prevention, the dandelions, chickweed and clover, which have overwintered, are waiting to bloom.

Coast to coast, dandelions reign as one of the most hated weeds by homeowners. Dandelions are a perennial weed present in lawns in the early spring, but are not yet actively growing. As soon as the temperatures start to increase and the rain comes, dandelions explode across lawns — and once the yellow blooms appear, the phone starts ringing. Most are customers calling to complain. Homeowners expect their lawns to be weed-free if they are paying a professional to do the service. The sight of dandelions brings about strong emotions — and not good ones.

There are many effective products on the market to control dandelions, but they typically should be applied later in the spring or summer when the temperatures rise and the weeds are actively growing. A product such as Defendor specialty herbicide provides postemergence control of dandelions and other high-anxiety weeds during preemergence timing, and can be applied in late fall or early spring. Designed to perform under cold-weather conditions, Defendor controls weeds early to help free up resources at critical times of the year when labor is limited.

Defendor has a different mode of action than the auxins; and when applied pre-bloom, it stops the emergence of the dandelion seed head while the herbicide slowly controls the plant. The end result keeps the declining weed below mower height and nearly invisible to the homeowner. This gives the LCO a much earlier start on controlling dandelions, ultimately providing more flexibility when scheduling and making applications.

This also is the ideal time to make crabgrass applications. A product such as Dimension specialty herbicide, with both preemergence and early postemergence control, will attack crabgrass prior to germination and prevent future outbreaks. Knowing when crabgrass is likely to be present is helpful in proper identification and control. Crabgrass germinates when soil temperatures reach a consistent 55 degrees Fahrenheit at a depth of 2 inches. Depending on the region, crabgrass may begin germinating as early as February and into May, and will continue to grow through August. If an LCO can get the crabgrass control down at the same time they’re making the winter broadleaf weed applications (late fall or early spring), an LCO could save a lot of time and money.

Timing customer renewals

Customer renewals also can play a large part in planning herbicide applications. The earlier an LCO renews a customer for the coming year, the better. It not only opens up a dialogue between the LCO and the customer, but it gives the LCO an opportunity to proactively address a customer’s concerns. The LCO already understands the customer’s weed problems, so they can make a prescriptive application and get ahead.

Early renewals can help an LCO plan their route in spring. The LCO can treat existing customers’ properties in fall, which gives the LCO more time to attract new clients at the beginning of the year. This is also going to increase employee morale and retention, because they aren’t dealing with customer complaints and callbacks.

Summer weed control

Summer postemergence herbicide applications are also effective, but they must be applied to weeds that are young and actively growing. In the north, use amine-based formulations of 2,4-D when temperatures are high and volatility is a concern. In warmer climates, adjuvants will improve herbicide coverage and help penetrate the waxy leaf surfaces of species such as broadleaf plantain and dollarweed. Be cautious with these additions to ensure they don’t increase the potential for turf damage. Irrigate only when necessary. Deep, infrequent irrigation is better for turfgrass than light, frequent irrigation. In the north, weeds like curly dock and sedges thrive in moist conditions.

Getting ready for winter

Fall fertilizer applications provide longer-lasting benefits to a lawn than those done at other times of the year. For best results, make one application in early fall and another six to eight weeks later. There are fertilizers designed for specific seasons, so make sure to use a fall fertilizer that encourages root growth. For troublesome winter annuals and perennials, such as dandelion, chickweed and clover, use a postemergence herbicide.

Application timings vary by geography. In the north, fall/winter herbicide applications can be done as early as Labor Day. In warmer climates, they can be applied as late as October. Fall also is a great time to aerate, reseed and dethatch before the dormant season. Dense, lush turf is the best way to reduce the spread and encroachment of winter annuals.

Educating your customers

Ultimately, a healthy lawn starts with proper homeowner education. LCOs should be talking to their customers about what they can do to support the LCO’s efforts. Proper mowing height, lawn mower maintenance, weed control, aeration and fertilization are all important. When LCOs engage their customers, they can work in tandem to create a successful weed-control program.

Jamie Breuninger is technical leader for Dow AgroSciences Turf & Ornamental. He is responsible for research and development for the U.S. Turf & Ornamental market. Breuninger joined Dow AgroSciences in 1990 as a technical service and development representative in Sacramento, Calif. He began his career with TruGreen Chemlawn as a technical manager, developing chemical programs for branches on the East Coast. He has a doctorate in agronomy from Pennsylvania State University.

Defendor and Dimension are trademarks of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. State restrictions on the sale and use of Defendor and Dimension specialty herbicide products apply. Consult the label before purchase or use for full details. Always read and follow label directions.

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