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Healthy lawn is best defense against summer turf diseases

Sparing your lawn from disease

Date published: 6/19/2009

TURF DISEASES CAN do anything from affecting the appearance of your lawn to wiping out large parts of it. Managing and preventing turf diseases involves a combination of practices that include maintaining a turf stand capable of fighting off disease and using pesticides when needed.

Any turf management plan must begin with proper identification of diseases. Many problems caused by humans and pets can be confused with diseases and complicate the initial diagnosis. Such issues include chemical burns from fertilizer and pesticides, dog spots caused by urine and dull mower blades.

There are many of environmental and manmade conditions that contribute to the development of summer fungal diseases. Prolonged leaf wetness and high humidity provide ideal conditions for the fungi to grow.

We contribute to this problem by watering our turf too frequently and at the wrong time of the day. The best time to water lawns is between 4 and 8 a.m., as this allows the leaves to dry during the day and prevents the fungi from getting a start. Deep, infrequent waterings--once or twice a week--are best.

Poorly drained soils contribute to the occurrence of fungal diseases. Improve drainage by aerating the lawn to reduce compaction and let more water soak in.

Heavy spring nitrogen applications can contribute to the development of brown patch, leaf spot and other diseases. Limit or better yet eliminate the use of nitrogen fertilizers in spring. Follow a fall fertilization program for fescue and other cool-season lawns that are most common in the Fredericksburg area.

Poorly balanced soil fertility is another cause of brown patch and other diseases. Get a soil test to learn how much fertilizer and lime should be applied, preferably in the fall, to keep soil pH and phosphorous and potassium levels balanced.

Daytime and nighttime temperatures can also aid fungal growth. Many of these diseases do well when daytime temperatures are between 60 and 90 degrees and evening temperatures drop to the 50- to 65-degree range.

Improper mowing can also encourage turf disease development. Grass cut with a dull blade will have a ragged edge, providing an entry point for diseases. Keep your mower blade sharp and mow cool season lawns to a height of 2.5 to 3 inches.

John E. Howe is an agent in Virginia Cooperative Extension's Spotsylvania County office specializing in animal science. Phone 540/507-7571; e-mail jhowe@vt.edu.

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Date published: 6/19/2009