U of G UPDATE
Are Root Diseases on the Rise in Ontario? B
ased on the diagnostic samples that have come to the GTI Turfgrass Diagnostic Clinic over the past three years, I used to wonder if root diseases were on the rise in Ontario or if we were just getting more of them because they are harder to self-diagnose. However, after visiting numerous courses in person and speaking with a number of superintendents over the years, I would argue that root diseases are, in fact, more prevalent than they were a decade ago. The question is why? The purpose of this article is to briefly mention some of the root diseases that we see coming through our laboratory, list recommendations for these diseases as a whole, and finally to speculate as to why we are seeing an increase in these “silent killers.”
ATTENTION! IPM Certified Agents
The Usual Suspects The primary root diseases that we see on golf greens include Take-all patch (caused by the fungus Gaeumannomyces graminis) (Fig. 1), summer patch (Magnaporthe poae) (Fig. 2), Pythium root dysfunction (various Pythium spp.) (Fig. 3) and plantparasitic nematodes. In the samples received in the clinic from throughout Canada, about 50% of our diseased samples (meaning that we exclude those that end up being caused by abiotic, or non-living issues) are diagnosed with take-all patch. Approximately 15% have summer patch, 10% have Pythium root dysfunction (or cool-season Pythium) and about 10% have plant-parasitic nematodes. If we look at just what we see in Ontario, the numbers change a bit to 30%, 20% 10%, 5%, respectively. Either way, however, over 50% of the diseased samples that we receive in the clinic are diagnosed with some type of root disease. As I mentioned above, it is possible that part of this is because root diseases are a bit more difficult for superintendents to self-diagnose, often leading to a request for outside help, but that is certainly not the whole story.
1
2
General Recommendations
Get your recertification credits ON-LINE with
P.D. Solutions! Visit: www.pdsolutions.ca or call 1-877-977-6774 20 Green is Beautiful • Winter 2014
There are some common recommendations for root diseases in general, but many of them are not practical for today’s golf course superintendents. The first of these is increasing height of cut. This allows for greater area for photosynthesis, and, subsequently better root growth and recovery from stress. However, most turf managers are not willing to sacrifice ball roll distance for healthier turf as the demands of golfers will likely not allow it. Therefore, we recommend the following practices be followed to overcome some of the stress placed on plants that are cut exceptionally low: 1. Reduce soil compaction through frequent core aeration. Roots need large pore spaces to grow, especially when they are under attack. Core aeration creates such pore spaces
3
Fig. 1: Symptoms of take-all patch on a creeping bentgrass green. Fig. 2: Symptoms of take-all patch on an annual bluegrass green. Fig. 3: Cool-season Pythium on a mixed species green. Note the lack of pattern that could mimic abiotic damage.