Tech solutions to limit PGR overspray on collars

By |  June 7, 2022 0 Comments

Overspray of PGRs into collars and surrounds has long been a problem for turf quality. Like mechanical damage, this problem can be especially bad where warm-season grasses surround cool-season putting greens. However, recent research has shed light on how problematic growth regulator applications can be for any collar-height turf surrounding a putting green.

Photo: USGA

Photo: USGA

University of Nebraska research showed the degree of seasonal variation in PGR metabolism and how growing degree day (GDD) accumulation is better for predicting when superintendents should make reapplications than calendar days. Turf metabolizes PGRs more quickly under warmer conditions and superintendents need to apply PGRs more frequently to maintain consistent regulation than they do under cooler conditions.

This research also indicates that turf at putting green height requires more frequent applications of PGRs than fairway or collar-height turf to maintain steady growth suppression. Additionally, relative regulation at the same application rate is much higher on collar-height turf compared to green-height turf. Even when superintendents follow GDD models for putting green applications, overspray into collars can still lead to severe overregulation. The growth rate of the grass is inadequate to recover from traffic, which leads to a decline.


Covering collars with carpets during spraying, immediately washing PGRs off the collars after application or leaving small untreated strips around the edges of putting greens to prevent overspray are all options to limit this problem. One of the simplest and most effective solutions is to use GPS sprayers.

GPS sprayer technology limits overspray into nontarget areas, and individual nozzle control offers very precise application. It is not a perfect solution, but this technology can substantially reduce PGR overspray on collars.

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About the Author: Darin Bevard

Darin Bevard is the senior director of championship agronomy for the USGA.

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