News and Information
Controlling annual bluegrass seedbeds: spray now or wait?
Dr. Kevin W. Frank
Michigan State University
The quick start to the growing season this year has resulted in many questions regarding growing degree days (GDD) and application timing for Proxy/Primo to control annual bluegrass seedheads. The green wave of GDD reaching the application timing has swept into Michigan.
Many golf course superintendents use two applications of Proxy/Primo for managing annual bluegrass seedheads on putting greens. This combination has proven to be a reliable way to suppress seedheads and enhance turf quality in the spring. GDDtracker.net starts measuring GDD on Feb. 15 and uses anything over 220 GDD (base temperature of 32 °F) as a guide to making the first application. However, there are other factors that you should consider. Both products are foliar absorbed and need living, green, plant tissue for uptake. Applying Proxy/Primo to dormant turf will not be effective. The decision on when to apply Proxy/Primo should consider the following factors:
- GDD total greater than 220 (base 32 °F)
- Mowed at least twice
- Turf is 100 percent green
There is no benefit from applying your Proxy/Primo to dormant turf. However, if you have green-up, have mowed, and have already made an application the cold temperatures should extend control. Air temperatures drive the metabolism of Proxy. Part of the reason that the application range is so generous is that in cold weather it takes longer to get active in the plant and in warmer weather it gets active faster. The activity of Proxy/Primo will either be ‘extended’ by cold weather or ‘activated’ by warm weather.
Typically, the second application is made 14-21 days after the initial application. Temperatures are forecast to be cold for the next week so the second application could be delayed a week or more, as the product will remain in the plant longer in cold weather.
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