Inflation has hit the golf industry just as it has impacted almost every other area of our lives. Fertilizer and pesticide costs, which are directly linked to fossil fuel and energy prices, have become more expensive. Some herbicide applications cost $200 per acre, or more. For 25 acres of fairways or 70 acres of rough, there is a hefty price tag that comes with broadcast treatments. As a result, many golf courses are utilizing spot treatments to manage emerged weeds.
When deciding whether to broadcast spray or spot spray, herbicide cost can certainly be a factor, but keep in mind that there are very cost-effective herbicides that can be applied at less than $2 per acre that can substantially reduce the weed pressure prior to spot spraying. Subsequently, the areas requiring a spot spray and the frequency of spot spraying can be reduced. It’s also important to remember that while spot spraying can reduce the overall cost of the herbicides due to smaller areas being treated, any savings is at least partially lost based on the labor and time involved in having one or several members of a maintenance crew scouting the course and treating weed outbreaks. Some courses are doing this monthly or evenly weekly through the growing season, so the labor costs can add up. There is also the sometimes unsightly appearance of dead weeds and grass in spot-treated areas and the risk of an unfortunate golfer’s ball ending up in a spot spray herbicide crater.
Another challenge with spot treatments is delivering the desired application rate. Herbicides are labeled with rates per area treated, but converting those directions to the volumes applied as a spot treatment can be tricky. From my experience conducting pesticide training sessions, after directing someone to use their best judgement in spot spraying an area with 2 gallons per 1,000 square feet as the objective, 95% of the participants applied two to four times greater than the 2-gallon rate. Spraying an herbicide mixture at four times the desired rate can easily cause turfgrass damage.
BMPs for Spot Spraying:
Calibrate the sprayer with the person making the application. Measure out a 500-square-foot area, fill your sprayer tank to a fixed volume, and instruct the spray technician to spray this area to what they deem good coverage. When finished, measure the water left in the tank to determine what volume was sprayed and adjust your application accordingly.
If you are thinking about applying an herbicide mixture for postemergence treatment, start with one herbicide first and then test the effect of adding a second. Sometimes combinations of herbicides can be more or less effective or more or less damaging to your turfgrass. Leave the surfactants out unless the label calls for these additions. If the weed populations being sprayed are very dense and the herbicide(s) kill the weeds very quickly, a new crop of weed seedlings can spring up in the voids. Adding a short-residual preemergence herbicide may be beneficial in keeping seedling weeds out while the grass fills back in.
Preventing weeds from becoming established in turfgrass is analogous to managing our own health. A good diet, exercise and a generally healthy lifestyle is the best prevention against diseases or health maladies. Maintaining a dense, healthy turfgrass canopy with complete coverage denies weeds the platform to become established. Unfortunately, cart traffic, shade, divots and anything else that leads to turfgrass thinning creates an opportunity for weeds. An ounce of weed prevention is worth pounds and pounds of repeat “cures” and yields a better playing surface for all.
Southeast Region Agronomists:
Chris Hartwiger, director, USGA Course Consulting Service – chartwiger@usga.org
Steve Kammerer, Ph.D., senior consulting agronomist – skammerer@usga.org
Jordan Booth, Ph.D., agronomist – jbooth@usga.org