Brown needles often indicate a health problem in pines. The evergreens get their name because of their ability to retain green, waxy needles all year round, even during the winter. Identify the source behind the discolouration as soon as you notice brown needles so you know the exact cause. Care for brown needles on the pinus tree to restore it back to its health.
Fungal diseases such as Dothistroma needle blight, brown spot needle blight and Lophodermium needlecast cause the needles of pine trees to turn brown and appear burnt. Caused by the fungus Mycosphaerella pini, Dothistroma needle blight causes the needles to turn brown at the tips, while they remain green at the base. Snip infected parts of the pine tree and apply a registered fungicide to control spread in the summer. Minimise plant stress and practice good sanitation to prevent future outbreaks.
Severe drought, coupled with insufficient watering, causes the needles on a pine tree to turn brown. Because pines thrive in well-draining, slightly acidic soils, overly dry soils prevent the roots from absorbing nutrients, thus causing dehydration and increasing plant stress. Dehydrated trees are more susceptible to diseases and pest infestations. Regular irrigation, especially during dry periods, helps the tree restore green, healthy needles.
Pests including aphids, spider mites, pine shoot borer beetle and Zimmerman pine moth infest young and established pines, causing the needles to turn brown. Aphids and spider mites drain sap from the needles with sucking mouthparts, causing them to turn brown and wilt. Newly hatched larvae of Zimmerman pine moths feed on the stems, causing them to girdle and the needles to turn brown. Pine shoot borers cause stunted growth and brown needles in small pine trees. Spray small infestations of bugs with water or horticultural oil, or apply a registered insecticide to deter heavy infestations.
Some needle loss is natural for evergreens, including pines. Similar to leaves, older needles turn brown and fall off the tree to make way for younger growth. Although needle drop is a natural phenomenon, examine a sudden or severe loss of needles to determine whether it is related to pests or disease. Winter injury also causes the needles of pine trees to turn brown. Trees exposed to extreme temperatures and drying winds in winter or spring turn brown. In most cases, the needles restore their original colour with the onset of warmer weather. Pines also turn brown due to physical damage, transplant shock and animal injury.
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- Ohio State University; Why Are My Pine Needles Turning Brown?;Dr. Tim Rhodus; 2002
- Michigan State University; Why Are My Pine Trees Turning Brown; Dennis Fulbright, et al.; April 2011
- University of Saskatchewan; Browning of Evergreens Can Be Controlled; Grant Wood
- Oklahoma Cooperative Extension; Why Are My Pine Trees Dying?; Tracey Payton
- North Dakota State University; Diseases and Related Problems of Evergreens; September 1997