Cultural Management Can Limit Damage From Disease

Turfgrass diseases can create many headaches for golf course superintendents, and it is tempting to rely on magic bullets to cure them. However, cultural practices are really the foundation of a turfgrass disease control program.

It might surprise you to learn that natural biological control of turfgrass diseases is actually the norm in turfgrass ecosystems. Natural field soils commonly show some degree of disease suppressiveness; this is easy to demonstrate experimentally. However, the problem is that this natural biological control is usually insufficient for complete disease control, so turfgrass managers still must contend with disease outbreaks. Maybe as we learn more about the complex world of natural biological control, we'll be able to recommend ways to consistently treat turfgrass disease.

Quick Tip

The use of commercial biological products for controlling diseases is increasing in turfgrass management. This is a wonderful development, but unbiased research shows that the efficacy of the current generation of biological control products is typically not as consistent as inert fungicides. Compost teas — room-temperature water extracts of composts — are being increasingly used for turfgrass management, but to my knowledge there is not yet been any published research on the effectiveness of these against turfgrass diseases.

With commercial biological control agents, expect variability in performance from site to site and from year to year. Furthermore, don't expect good results under high disease pressure. And exercise some healthy skepticism of exciting claims of disease control. Rely on cultural practices and resistant varieties as the foundation of your disease control program, and don't expect the application of biological control products and compost teas to substitute for good agronomics.

Variety selection

If you are seeding or re-seeding, selecting a variety resistant to important turfgrass diseases is among your most potent tools for reducing disease pressure (Photo 1). If you managed a variety highly susceptible to the patch diseases pictured there, you could likely never use enough fungicide to completely control these soil-borne diseases. However, by choosing a variety with a high level of resistance, you can see you would be able to avoid the use of fungicides for patch diseases.

Differences in susceptibility to summer patch and necrotic ring spot among Kentucky bluegrass cultivars.

It is sometimes tempting to ignore disease resistance when selecting varieties. For example, some practitioners are unconcerned about the high susceptibility to dollar spot in some creeping bentgrass varieties, pointing out that fungicides can be used to control this disease. But not only does this lock you into a fungicide dependency, it increases the risk of fungicide resistance by increasing overall pathogen activity, possibly creating a situation where fungicides become less and less useful for the very disease you are trying to control.

Incidentally, excellent information on disease reactions of varieties is available through the National Turfgrass Evaluation Program (http://www.ntep.org/).

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