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November 7th, 2017

A Proactive Approach to Treating Leaf Spot

Article by Ian Collins

With the risk of disease, drought and other unfavourable conditions compliments of Mother Nature, combined with the wear and degradation golf courses are exposed to year-round, your turf is constantly being put to the test. Leaf Spot/Melting Out on turf is one disease in particular that we can expect to make its mark on golf courses across the south where Bermudagrass is prevalent this fall and throughout the winter. The destructive fungi is caused by species of Drechslera and Bipolaris (formerly known as Helminthosporium). In the bluegrasses, this disease is most active during warm and humid weather. In Bermudagrasses, most damage occurs during cool and wet periods in the fall and spring, especially during periods of prolonged cloud cover.

The best way to keep your turf healthy, strong and at peak performance is to stop diseases such as leaf spot before they even start. Turf experts agree the only way to do this is through a preventative and proactive approach that better equips the plant to withstand stresses on an ongoing basis. However, knowing what to look for and how to diagnose your turf will help you cure a bout of Leaf Spot if it does makes an appearance on your turf.

Keep an eye out
The unsightly disease generally surfaces in warmer climates September through March and is characterized by off-colour and bruised-looking turf. A variety of bluegrasses and Bermuda grasses are susceptible including Kentucky bluegrass, perennial ryegrass, bentgrasses, tall fescue, and fine fescues. Symptoms first appear as small, brown or black spots or flecks on the leaves or sheaths. As the lesions expand, the center of the lesions becomes tan with a dark brown or black border. The lesions may also be surrounded by a yellow halo. As the lesions expand, they coalesce and cause dieback of entire leaves or plants.

Leaf Spot is most severe on turf that is growing slowly due to adverse weather conditions or improper management practices. Shaded areas with little or no air movement result in weak turf and extended periods of moisture, favoring disease development. Deficient or excessive nitrogen, excessive thatch, low mowing heights and other stresses such as drought also encourage disease development.

How to treat leaf spot
Knowing what to look for and when will help in faster identification and treatment of the disease. In terms of chemical control, fungicides including DMIs or Strobilurins are the go-to fix and applications should be made as soon as the disease is discovered. Timing is critical. Leaf Spot left to its own devices will spread and as a result require multiple treatments. Even then, there is no guarantee that the late applications will be effective. 

Cultural control can also help mitigate the effects and severity of leaf spot. Superintendents can adjust the following turf management practices for a better outcome:

  • Decrease nitrogen use
  • Avoid close mowing which gives the pathogen easy access to the plant’s crown and roots
  • Irrigate deeply and infrequently to allow the leaf to dry between watering periods
  • Use lightweight equipment to reduce turf stress

Richard Latin, Professor of Plant Pathology at Purdue University encourages superintendents to double check their diagnosis before treating. Leaf Spot can resemble gray leaf spot which is caused by an unrelated pathogen and is only responsive to specific fungicides at specific times of the season. Note that gray Leaf Spot will only grow on tall fescue, perennial rye and St. Augustine, with temperatures falling between 70 and 95 degrees Fahrenheit. Attempting to solve the wrong problem will not only be costly and time consuming but also damaging to your turf.

Protect your turf with CIVITAS TURF DEFENSE
Superintendents who look beyond traditional fungicides focused on the pathogen alone will find holistic solutions designed to enhance plant protection all season long. Applied preventatively as an integrated component of your IPM program, CIVITAS TURF DEFENSE is a fungicide, insecticide and plant protection product that protects against biotic and abiotic stresses. This way, you can actively protect your turf all season long before stresses like Leaf Spot get a chance to take hold. There’s no time like the present to plan for the future of your turf.


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