Of all the maladies of turf, both biotic and abiotic, pathogens are the most elusive to control, particularly in the lawn care business. Diseases tend to require more frequent scouting/monitoring, are more dependent on seasonal weather influences and are more easily confused with other agents that negatively impact turf such as insects, weeds and nonliving factors. When added to the limitation of the amount of time that a turf manager is able to spend with a given lawn as well as the lesser degree of control for overall management that exists with other turfgrass sites (golf courses, sports fields, campus grounds), disease management and control is just plain difficult for the lawn care operator.
What are the top five worst turf diseases?
1. Leaf Spot/Melting Out. Prolonged dry periods that alternate with cloudy, wet weather in spring favor the development of leaf spot. Key symptoms are brownish-purple lesions on turf blades. As the disease progresses to the leaf sheaths and crowns, they become darker and cause the leaves to turn entirely yellow and fall from the plant. The overall effects are thin stands with dead and dying crowns, which is problematic as all new shoots and roots are initiated therein.
2. Dollar Spot. Under weather patterns of warm days and cool nights that produce dew and high humidity in the turf canopy, mycelium on the grass blade surfaces are produced. Dollar spot can occur over a wide range of time, from late spring to mid-fall, especially if fertility is low. The disease produces softball sized spots in lawns, with blade symptoms of individual lesions that transition from green to medium brown to bleached to medium brown to green. Several lesions commonly appear on an individual leaf, causing the blades to die.
3. Summer Patch.Summer patch appears as 6- to 18-inch semi-circular to serpentine patches that are expressed as pockmarked or doughnut-like shapes. The dead grass is uniformly tan, with tufts of apparently healthy turf mixed in the patch. The key indicator of this pathogen is the rotting of the roots in midsummer, initiated in early to midspring. In most situations, summer patch remains in a turf stand for several years if not preventively treated.
4. Stem Rust. From a distance, heavily rusted turf takes on a yellowish to orange appearance. Upon closer inspection, orange to brick-red pustules are evident on grass blades. Spores within these pustules rub off easily when touched. Stem rust is usually more rampant under hot, dry conditions when growth has slowed in late summer. At this point in the season, plants may be under low fertility and less vigorous than necessary to resist infection.
5. Brown Patch. In lawns, expression of the disease is the presence of patches or rings of dead and dying turf, usually between 1 and 2 feet in size. Green plants in the patches have leaves with long, irregularly shaped ash-gray spots or lesions that are surrounded by a dark brown margin. In the center of the spot, the blade appears beige in color.
Use the multiple strategy control approach
Sound cultural practices go a long way in the overall management of turfgrass diseases.
- Resistant cultivars — Renovate turf to incorporate the latest area-specific, NTEP-researched cultivars.
- Increase air circulation — Remove nonfunctional trees, shrubs and fencing and/or coordinate crown cleaning with an ISA Certified Arborist.
- Consider amount of shade — Turfgrass is a sun-adapted plant; evaluate the number of hours of direct sun that the lawn receives.
- Improve infiltration — Aerify the lawn and consider topdressing with organic matter.
- Moderate fertility levels — Apply nutrients as recommended by the land grant university closest to your location.
- Moist moisture — Irrigate just enough to keep turfgrass healthy.
- Right plant, right place — Turfgrass and ornamentals require different levels of irrigation. Take into account factors such as slope and shade.
- Scout and monitor — Keep a record of lawn areas that tend to become diseased from season to season so you can treat them preventively.
Chuck Monico Sr. with CM’s A Cut Above Lawn Service concurs with the focus on multiple strategies. “We will see any number of fungal diseases in a given season: dollar spot, brown patch, summer patch, powdery mildew, rust. In all cases, we preach cultural practices as the best defense. This includes irrigation based upon the needs of the turf in the early morning, proper fertilization for the time of the growing season, mowing high to help reduce stress on the turf, aeration on a regular basis and periodic overseeding with disease-resistant cultivars. Reducing shade and improving air flow in the yard can also help with some diseases. Most of the diseases we see will recover with changes in temperature and humidity.”
Monico offers a preventive three-application, granular fungicide protocol, consisting of triadimefon (Bayelton) followed by two applications of fluoxastrobin (Disarm G).
“Typically, we use an April, May, June schedule,” he says. “We would not use the same chemistry more than twice in a row, and we continue to explore different chemistry combinations. Back to back applications of Propiconazole have been used in selective situations as a rescue product.”