Spot treatments have become a popular approach to managing localized problems on golf courses. In my experience, spot treatments are most often used to target localized weed outbreaks with one or more herbicides mixed together.
With label differences from one product to another, there can be confusion around the product limitations for spot treatments. Before making a spot treatment, read the product label carefully. In some cases, a spot treatment will allow for a higher application rate compared to a broadcast application rate. However, this often requires that the total area receiving the application is not greater than 10,000 square feet. There is also usually a maximum number of times that a spot treatment can be applied per year.
The label:
As an example, let’s look at spot treatments for parasitic nematodes. Using a fictional product, ‘Nem-away’, the label states it can be applied twice per year at the low rate of 8 ounces per acre or once per year at 16 ounces per acre. The maximum allowable amount that can be applied per acre per year is 16 ounces. Nem-away allows a spot treatment of 16 ounces to no more than 10,000 square feet. A maximum of four spot treatments are allowed each year. These spot treatments can be made to either the same or different areas as long as the area does not exceed 10,000 square feet.
The scenario:
A golf course wants to apply Nem-away within label stipulations. They have nine problematic greens they want to treat, which total 40,000 square feet. All eighteen of their greens encompasses 2 acres. Treating all nine problematic greens hits the limit of four spot treatments of 10,000 square feet. Afterwards those greens have been treated, no additional Nem-away can be applied either via additional spot treatments or broadcast applications to these greens or any other greens on this golf course because the maximum amount of 16 ounces per acre has been met. Even though the other greens were not treated, they are included in the total maximum acreage for the product. In this scenario, the course applied 64 ounces of product across 2 acres of greens (even though only 9 greens were treated), which results in a 32 ounce per acre per year rate. This course is sacrificing treatable acreage for areas not treated in order to apply more product to this targeted, smaller area.
The implications:
What are the implications of overapplying any one product? Each product labelled for use on golf courses have annual use limits to avoid nontarget effects such as impacting beneficial organisms like bees. Another concern that can be overlooked is the development of resistance or inadvertently causing an increase of insensitive strains of either nematodes, weeds, insects, or diseases.
This was just one example of spot treatment directions. Other labels may allow for a higher number of applications but to the same limited area of no more than 10,000 square feet. Spot treatments can be a great way to focus efforts and applications to small problematic areas, thereby minimizing unnecessary applications to healthy areas. They can also save time and money when done correctly. If the label is confusing, check with your distributor or manufacturer to get the details correct. You can also check with your local extension agent or your USGA agronomist for help.
Southeast Region Agronomists:
Steve Kammerer, Ph.D., regional director – skammerer@usga.org
Chris Hartwiger, director, Course Consulting Service – chartwiger@usga.org
Addison Barden, agronomist – abarden@usga.org
Information on the USGA’s Course Consulting Service