MULTIPLE APPLICATIONS CARLSON 169

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1 CARLSO 169 ETHOFUMESATE FOR COTROL OF AUAL BLUEGRASS O GOLF COURSE FAIRWAYS T.M. Carlson and B.E. Branham Departmt of Crop and Soil Scices Michigan State University, East Lansing, MI Annual bluegrass control has be and continues to be a major hurdle for golf course superintdts to overcome. Ethofumesate has shown in the past and continues to show that it is effective for annual bluegrass control. Prograss is a herbicide that selectively controls annual bluegrass. This paper will discuss some rect research conducted at Michigan State University and also compare several past studies to the rect research. MULTIPLE APPLICATIOS In September of 199 a study was initiated with additional applications in October, ovember and/or April at Detroit Golf Club. Only two rates were used in this study.75 and 1.5 Ibs a.i.la. All combinations of.75 and 1.5 lbs a.i.la gave significant control of annual bluegrass from the control treatmts (Table 1). All treatmts with one or more 1.5 lbs rate(s) gave significant control of annual bluegrass, but the perct ground cover would be unacceptable in a fairway turf. With the.75 lbs September lbs October treatmt being the only exception. The April applications gave the most surprising results. The perctages of annual bluegrass in the April treatmts were less wh compared to the equivalt Sept., Oct., and/or ov. treatmts. Injury was severe on treatmts with 2 or more 1.5 lbs applications and is not recommded. Injury was rated on a 19 scale with 1 being completely dead and 9 showing no injury. The spring injury rating was evaluated before greup had started and all injury had recovered by the d of April. Multiple Prograss applications of.75 lbs a.i./a with 3 applications in the fall and 1 application in the spring significantly controlled annual bluegrass.

2 17 GOLF TURF MAAGEMET REOVATIO This study has be repeated for several years and continues to reaffirm what we have se in the past. Two injury ratings were tak, one in the fall of 199 and the other in the spring of 1991 (Table 2), using the same injury scale explained earlier. The treatmts gave no unacceptable injury 6), and noticeable injury to the turf recovered by the first part of May. Evaluating the safety of Prograss on newly established btgrass was only one objective of this study. The other was to control the reinvasion of annual bluegrass (Table 3). All treatmts resulted in significantly less annual bluegrass than the control plots, with.38 2 WAG (week after germination) WAG on the first seeding date being the only exception. Again this year we had more annual bluegrass in our early seeding dates th in our late seeding dates. The recommdation from Michigan State University in the past has be to begin fairway rovation in midaugust so that there's a well established stand of turf before annual bluegrass germination in September. One possible explanation for better annual bluegrass control on the later seeding dates is that Pro grass has only little pre emergce activity. As the early seeding dates are treated annual bluegrass hasn't yet germinated. Wh the later seeding dates are treated annual bluegrass has germinated making the treatmts a post application therefore giving more activity on these seeding dates. Another explanation may be the need for cold temperatures prior to Prograss applications. The early seeding received Prograss applications by the first of September before any cold temperatures were countered and most of the final applications on the early seeding dates wt down prior to cold temperatures. Again this year our best results were.75 lbs a.i./a at 4 WAG with an additional application. All treatmt combinations did give us significant control of annual bluegrass and no unacceptable injury, but the control of annual bluegrass was not as good as the.75 lbs a.ija at 4 WAG. Some treatmts combinations also had a ground cover below an acceptable level for a fairway situation. Ground cover ratings were based on the amount of developed turf. An acceptable level of ground cover would be anything above 97%. PREEMERGECECOTROL In the fall of 1987 a study was initiated to evaluate Prograss as a preemergce control. This study gave us excellt results. All rates of Prograss gave good control of annual bluegrass in comparison to the check plot (Table 4). In the fall of 199 we initiated a study to develop a pre emergce strategy for annual bluegrass control. A fairway type area was used and the turf was kept in the most natural state. First the preemergce herbicides were applied and th watered in. Th evaluation circles 1 1/2 inches in diameter were killed with Roundup. There were two purposes for the circles. One was for evaluation purposes because every two weeks we would count the number of new germinants in these circles and th respray with Roundup. The second reason was to keep the turf in a natural state and not dramatically effect the microclimate, moisture level, and/or ultraviolet rays reaching the soil surface and affecting the preemergce barrier. Results showed little or no control of annual bluegrass was achieved with Prograss under these conditions (Table 5). The same type of study was repeated in 1991 much like the 199 study. Again a fairway like turf area was used. The herbicides were applied and watered in. Evaluation circles were again used for evaluation purposes. This year we had no significant control of annual bluegrass wh compared to our check plot (Table 6). This raises the question of why was Prograss so effective in the bare soil study but gave little control in the fairway turf studies. The bare soil study area was rototilled, incorporating the thatch layer into the top 46 inches of soil and brought soil to the surface. In the fairway turf study the turf was left in a natural state. In the bare soil study, there was little organic matter on the soil surface. Thus, the presce of organic matter may be binding the Prograss making it ineffective for preemergce control.

3 CARLSO 171 SUMMARY Post emergce application of Prograss has shown to give excellt control of annual bluegrass. Multiple Prograss applications of. 75 lbs a.i./a with 3 applications in the fall and 1 application in the spring showed significant control of annual bluegrass with little if any undesirable effects. Using Prograss in rovation has consisttly giv us annual bluegrass control leaving predominantly creeping btgrass plots. Our best results have be at.75 lbs a.i./a at 4 WAG with an additional 1 or 2 applications. Preemergce applications with Prograss for annual bluegrass control hav't be as successful as postemergce applications. Bare soil applications of Prograss gave excellt control. The fairway turf study showed that Prograss was not as effective at controlling annual bluegrass as in the bare soil study. This may be due to the presce of organic matter at the soil surface.

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7 CARLSO 175 Table 4. Annual bluegrass control with preemergce application of Prograss on bare soil. Prograss Ibs AlIA Control % Annual Blugrass 4/12/88 5/2/ LSD (P =.5) Table Annual Bluegrass control with preemergce application of Prograss on fairway turf. Prograss Ibs AlIA Control LSD (P =.5) Perct Control 1/22/ Table Annual Bluegrass control with preemergce application of Prograss on fairway turf. Prograss Ibs AlIA Control LSD (P =.51 Perct Control 1/22/