Symptoms and Signs:

	Fig. 1
Fig. 2

The overall symptoms of Septoria resemble scorch, dull mower blade damage, or dollar spot (Fig. 1). Leaf blades yellow from the tip downwards. Lesions are tan or grayish. When the lesions enlarge, they girdle the leaf, causing tip blight (Fig. 2). These leaves die, resulting in thinning patches of turf. Eventually, little black pustules, called pycnidia (pycnidium in the singular), develop and can be seen with a magnifying glass or hand lens. The pycnidia are a key diagnostic sign for this disease, and allow you to eliminate dull mower damage or winter injury as the cause of the thinning patch.

Epidemiology:
Each pycnidium contains tens of thousands of long, needle-shaped spores. The fungus spreads by wind and splashing water, shoes and mower blades. The spores can infect injured leaves, particularly if a film of water is present. The cycle is repeated every seven to 14 days as long as the temperature remains between 60° and 75° F. The fungus overwinters in infected grass as pycnidia and as fungal threads called mycelia.

Management:
Frequently, the only course of action considered by the homeowner is using a fungicide. Currently, only fungicides containing Myclobutanil (e.g., Eagle WSP) are labeled for the control of Septoria leaf spot on turf. However, before you apply fungicides, keep in mind that most disease situations on home lawns and landscape turf can be adequately managed without fungicides. Alterations in cultural practices, renovation with resistant cultivars or species, or even very simple procedures can help.

Cultural practices should promote an environment that is not conducive for pathogen infection and disease development. As always, use grass (sod, plugs, seed) that has been selected to tolerate the harsh conditions of Minnesota. When mowing, remember the 1/3 rule: Only remove 1/3 of the grass whenever you mow. Removing more than 1/3 causes additional stress on your grass. Recommended grass height is 3". This means you should mow when the grass blades reach 4.5" (approximately 10 to 14 days). As always, keep your mower blade sharp and never mow when the grass is wet!

Conditions that contribute to Septoria include thick thatch layers and compaction. De-thatching and aeration can remedy these two situations. Remove excess thatch in early spring or fall, and core compacted areas once or twice per year. Try to minimize foot traffic in compacted areas until the lawn has recovered. In high maintenance yards, dead patches should be reseeded with Septoria resistant cultivars, like 'Adelphi,' 'Majestic,' and 'Nugget.' Homeowners who follow low-maintenance practices should reseed with the cultivar 'Park,' which has intermediate resistance to Septoria. Phosphorus application is still permissible when establishing grass seed and will aid in grass establishment. Do not use broad leaf weed control as these herbicides can damage newly emerging grass.

Low nitrogen levels have been associated with this disease problem. A soil test can be performed to determine whether nitrogen deficiency is contributing to infection by Septoria. Information about having a soil test performed can be found at the University of Minnesota's Soil Testing Laboratory (http://soiltest.coafes.umn.edu/).

P319P
Revised 2/2000
Chad Behrendt, Crystal Floyd