TURF TALK
By Patrick O’Brien and Chris Hartwiger
The summer of 2003 has brought more than extreme amounts of rain to golf courses in the southeast. A new disease on bentgrass putting greens has been identified on at least 10-20 courses in the Carolinas.
Here’s What We Know Dr. Lane Tredway, plant pathologist at North Carolina State University, has been the leader on this issue. Outlined below are his comments: “I am seeing an unusual disease of bentgrass in NC …. These symptoms started to show up about a month ago (early July) in certain places, but I have seen an explosion of new cases in the last few days, including several high profile courses. The problem is mostly on new greens (1-4 yrs old) and it has affected several cultivars (A-1, A-4, G-2, Crenshaw). The disease appears in distinct patches ranging from two inches to two feet in diameter. The symptoms are very similar to take-all patch or summer patch. The patches initially show signs of wilt and stress then continue to decline and turn yellow or orange in color. In one case, no fungicides with algae activity were applied, so algae invaded the centers of the patches, resulting in a dark-colored patch with a yellow or orange periphery. In plugs from affected areas, I see reddish brown necrosis of the crown, nodes, and to a lesser extent the roots. Lots of ectotrophic hyphae and simple hyphopodia are present on the surface of the necrotic tissue. There is no evidence of foliar blighting, and I have not observed Pythium oospores or sporangia on a consistent basis. What has me puzzled is that the disease appears to move in water. It usually appears first on higher, drier areas of a green and progresses downhill to lower areas, but still develops in distinct patches. Furthermore, when a patch develops on a slope, it is often oval in shape and elongated along the flow of surface water. This appears to be the same disease we saw last year and we were 38
TENNESSEE TURFGRASS OCTOBER/NOVEMBER 2003
calling take-all patch. I isolated Magnaporthe poae and Gaeumannomyces cylindrosporous from samples last year and have completed Koch’s postulates for both species. However, the movement in water really makes me wonder. “Summer Crown Rot” is the new disease affecting bentgrass putting greens in the Carolinas this summer for the first time ever. From our trials, we have identified three treatments that are very effective for suppressing this disease, which I am tentatively calling “summer crown rot”: 1. Chipco Signature (4 oz) + Fore (8 oz) 2. Subdue (1 oz) 3. Cleary 3336 (8 oz) + Heritage (0.4 oz) watered in with 1/8”
We have been applying these on 14 day intervals and are getting excellent control. The jury is still out on the efficacy of Terrazole. Fertility seems to be very important for recovery – 1/8 lb of N a few days after the fungicide induces very rapid recovery. Greens under lower fertility levels seem to have these symptoms more than sites with higher fertility levels. For now, I am recommending that superintendents with this problem follow this program. We have a site where we can set- up research plots and determine which of these applications did the trick. If you suspect an outbreak of this unusual disease, contact Dr. Tredway. We will continue to report any new information as it becomes available. T Source: Patrick O’Brien 770-229-8125 or patobrien@usga.org and Chris Hartwiger 205-444-5079 or chartwiger@usga.org
Email TTA at: tnturfgrassassn@aol.com