Firstly for those who don't know what Rescue is, it is a selective herbicide that kills Rye grass in turf. It is a relatively new product in the UK. Rye grass is a real problem on the surrounds and some fairways at M & N GC. I decided to do a few trials on the practice area last year to determined the best time in the year to use the product.
I did the first trial in July 2011, I sprayed an area 5m x 5m on fairway grade turf containing Rye grass, an area 2m x 2m in semi rough grade turf containing Rye grass and an area 10m x 6m spanning across the edge of the practice green and onto the surround. The last plot was 3m on to the edge of the green and 3m into the surround, the surround had very bad clumps of Rye grass, however the green did not contain any Rye grass. The idea behind trialling greens turf was to ascertain weather it would effect the long term health of the green if the product was used across the golf course greens. The product label does state it will effect different species of grass in different ways. Annual Meadow Grass and most Fescues are resistant to it's mode of action, however some bents are susceptible especially Highland bent. The green was seeded with a bent/ fescue mix, Manor and Denso being the bent varieties. The turf is now mostly a bent/ poa mix. All areas were sprayed at a rate of 1 l/ha using a knapsack sprayer.
After around 3 weeks all areas showed positive results and all the Rye grass was dying off . After 6 weeks the Rye grass had been removed and the remaining grass started to fill in the areas.
With the trial a success we sprayed 11 surrounds on the course and 2 fairways (the 14th and the 21st) in August. The results were very similar to the trial and 95% of the Rye grass has been removed. The worst areas for Rye grass cover were over seeded with a bent/ fescue mix to aid recovery. Nearly a year on and the results are still very positive, some of the most vigorous Rye grass has returned in small quantities but another application this year will reduce it further. Other surrounds will be sprayed this year to help improve the quality of our course.
One point of interest we have found since doing the trial on the greens turf mentioned above, is the fact is has since weakened the bent grass in the treated area. The bent didn't seem to be effected at the time of treatment, however over the winter period the bent sward has not recovered like the rest of the same green. We over seeded the practice green in October 2011 and the bent/ fescue spots where we over seeded into hollow core holes can clearly be seen in a poa dominated sward.
In both pictures it is clearly visible that the treated area is on the left and the unaffected, non treated area is on the right.
Here is the practice green in question, the effected area is on the left of the green, 3m in from the edge and 10m from the front towards the back of the green. There is a distinct line which shows, left poa sward, right bent sward.
I am not doubting that Rescue is a fantastic product, it has worked perfectly on surrounds, fairways and semi on the course with no negative results like this. The only explanation for this result is that the application period in July can not have been suitable in this instance, either weather conditions or growth at the time have stressed the treated bent enough to kill off some of the plants. Like I stated earlier in this post it does effect some bents, the bent grass used on this particular green is not Highland bent, so we can rule that out. Manor and Denso are high up on the STRI rating list so they are not poor species. Trials done elsewhere in the country have suggested that when bents are effected they are leaf scorched, but do grow back within a short period of time as the root system is not effected. In this instance the bent grass has died off over a longer period of time, with noticeable results after the winter weather. I will monitor this area closely and post my results in due course.
