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Proxy/Primo Timing and Rates
As the rain falls, temperatures rise and the grass gets greener our thought turn to properly timing Proxy/Primo tankmixes on creeping bentgrass/annual bluegrass turf stands. Current thinking from MSU, based on the recent success and failures, suggests that superintendents wait for two mowings after full green-up or 200-250 growing degree-days on the GDD32 degree-day model. Results from 2003-05 showed greater success when the initial application was made earlier. We had declining results with each initial timing between 309 and 548. Our best results in 2004 were with the 309 initial timing and decreasing slightly with each of the following initial timings. The results from 2005 indicated that even earlier initial timings were more effective. The second application should be made 21 days after the first. In nearly every case, two applications has performed better than one.
Fairways
Research at MSU strongly suggests using 0.2-0.25 fl oz. of Primo with 5 fl oz. of Proxy per 1000 square feet. Tankmixes that contained lower concentrations of Primo (i.e. 0.1-0.15 fl oz) did not perform as well in 2002 or 2003. Tankmixes of Proxy/Primo at 5 + 0.25 fl oz. per 1000 square feet provided seedhead suppression and turfgrass quality equal or better than all other treatments in 2003. Tankmix treatments that included the reduced rate of Proxy (3 fl oz.) did not perform quite as well as the full rate treatments but were still comparable to the Embark treatments in 2002 and 2003. If Proxy is used at reduced rates it may be necessary to apply a second application 21 days later. The label currently suggests using 5 fl oz. followed by 3 fl oz. This approach was used with good succes at the MSU west course in 2004. Overall the results from 2004 were disappointing, however, results from the same applications in 2005 were gerenally favorable.
The main advantages of the Proxy/Primo tankmix are the safening of the Primo on the annual bluegrass and the alleviation of the Granny Smith green color associated with Proxy on the bentgrass. There also seems to be some synergism with regard to seedhead suppression. Primo provides only a delay in seedhead expression when used alone. Although Proxy will reduce seedheads, tankmixes have provided better seedhead suppression than Proxy alone.
Greens
Primo rate should be reduced for greens applications. Proxy/Primo tankmixes for greens should be made at 5 + 0.125 fl oz. per 1000 square feet. If you plan on using Primo throughout the season you can start your program 14-21 days after the tankmix treatment.
Embark Timing and Injury
Embark is very effective at limiting Poa annua seedhead in the spring. However, significant turfgrass injury (yellowing) can be associated with Embark applications. Although the label lists rates of 4-6 fl oz per acre, most people are in the 3-6 fl oz per acre range. Embark injury can be exacerbated when frost events occur within two weeks after an application. Several GDD models exist for predicting Embark timing (many are available at this site). Research trials conducted by Michigan State University in 2001-05 indicate that maximum seedhead control and minimum turfgrass injury can be achieved when Embark is applied between 400-500 GDD on the GDD32 (4 out of 5 years).
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