Yellowing grass is disheartening and a cause for concern, especially when you invest precious time, money and energy on its establishment and maintenance. Several factors are responsible for causing the lawn or sections of it to turn yellow and appear burnt. Identifying the underlying cause helps treat the problem appropriately and keep it from recurring.
Yellow grass sometimes occurs as a result of severe insect infestation. Insect pests such as scale and grubs feed on grass roots, while chinch bugs, mites and leafhoppers suck sap from grass blades, causing the grass to wilt and turn yellow. Although specific treatment varies according to the type of grass and the insect responsible for damage, general control is achieved through insecticide application followed by heavy irrigation so the chemicals penetrate the soil to reach grass roots. In case of extreme infestation, a gardener has no choice but to remove the existing damaged grass and replace it with new grass.
Various diseases cause grasses to fade and turn yellow. Fungal diseases such as summer patch and Rhizoctonia yellow patch damage grass and cause them to take on a yellow appearance. Dollar spot and fusarium patch are other diseases responsible for yellowing grasses. Rust also causes grass to turn yellow, pale orange or light brown. Following a proper irrigation and fertilisation schedule avoids stress on the grass and reduces the chance of diseases. Apply a registered fungicide formulated to combat the particular disease to prevent it from spreading further on the lawn and help the grass regain its colour and vigour.
Improper Cultural Practices
Improper cultural practices are also responsible for yellowing grass. Although ideal mowing heights vary with grass types, most grasses thrive at a height of 2 to 3 inches. However, let the grass grow slightly higher during the summer or periods of drought. Avoid mowing more than one-third of the grass height in one session. While irregular mowing makes the grass susceptible to damage by pests and disease, mowing too frequently also puts undue stress on the grass, making it vulnerable to damage. Water the grass deeply but infrequently, giving it 1 to 1 1/2 inches of water every time. Water when it shows signs of wilt, which include mower marks or footprints that remain in grass one-half hour after the traffic passed. Lack of nitrogen fertiliser also causes grass to turn yellow. Feed the grass 0.454kg. of nitrogen fertiliser per 1,000-square-foot area.
Lawn grass naturally turns yellow during its dormant period, which varies according to grass type. For best results, choose grass that grows best in your area. Avoid planting warm-season grasses in cold areas since they grow dormant in fall and remain yellow until spring. Similarly, avoid planting cool-season grasses in warm areas.
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- University of Delaware; Lawn Diseases--Identification and Management; Robert P. Mulrooney; 2004
- University of California IPM: Nutrient Deificiencies
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- University of Illinois Extension: Sound Fertilizing Practices