Brown pine tree needles are often a sign of a health problem for pine trees. Evergreen trees get their name because their waxy needles allow them to remain green throughout the year, even in winter. Caring for a pine tree with brown needles is important for restoring the tree to health.
Some needle loss is natural for pine trees. Needles live for a few years before they turn brown and fall off of the pine tree; sometimes whole sections of the tree will turn brown and fall off at once before new needles grow and replace them. Needle drop is not always a sign of health problems, but severe or sudden loss of needles should be examined to determine whether the cause is related to disease or pests.
Pine trees that have contracted certain types of fungal disease may exhibit brown needles. The fungus Rhizosphaera needle cast causes pine needles to turn yellow, brown or even develop a purple colour. Fungal diseases infect pine trees through spores in the soil or that get into the tree through a wound from pest or physical damage. Applying a fungicide and pruning severely affected branches helps control the fungal infection and prevent it from harming the pine tree further.
There are a number of needle blights that can turn the needles of a pine tree brown. Dothistroma needle blight affects ponderosa and Austrian pines in particular, according to North Dakota State University. This type of blight causes needles to develop small spots that eventually cover and kill the needles. Controlling needle blights through keeping the soil healthy and, if necessary, applying chemical sprays helps reduce the damage caused by various blights.
Drought and infrequent watering can cause a pine tree to turn brown. Although pine trees grow best in slightly acidic and fast-draining soil, soil that becomes too dry prevents the tree from taking in nutrients and causes it to become weak and dehydrated. This opens it up to further pest and disease problems. Regular watering of a pine tree, especially in dry periods, helps restore the green needles and keeps the tree healthy.