The Homeowners Column

The Homeowners Column

What's Wrong with Pines

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator

Driving distractions are everywhere - billboards, bikers, walkers and talkers. For me it's desolately doomed trees or delightfully divine trees. For better or worse I respond to each discovery with equal enthusiasm.

Travel any street with a multitude of pines and you are sure to find a few sick ones. "So what's wrong with pines this year?"

First we have to rule out non-infectious diseases caused by the tree's environment or culture such as droughts, floods and planting too deep. The exact cause of infectious diseases depends on the species of tree. Each species has commonly occurring problems that may not affect spruces, other pines or other evergreens. So is it really a pine? Pines hold their needles in bundles of 2 to 5 needles depending on the species. Spruces are held singly on little woody pegs.

Scotch pine has short (1-3 inch long) needles held in bundles of two. Often the needles have a bad hair day twisted appearance. My 35 mile-an-hour diagnosis for declining Scotch pines is pine wilt. Pine wilt disease is caused by the microscopic round worms, pinewood nematodes. The nematodes ride from pine to pine in sawyer beetles. The nematode enters the tree through the beetles' feeding. Once inside the tree, the nematodes reproduce rapidly. The tree's water conducting vessels become clogged and the tree quickly dies.

Scotch pine is highly susceptible to pine wilt especially as they get to fifteen to twenty years old. The disease can also be found in Austrian pine and less commonly in red and mugho pines. White pines are resistant.

Sanitation is the most effective control for pine wilt. There are no known effective chemical controls for the disease, the nematode or the beetle. Affected trees should be burned or buried quickly before February in order to reduce spread.

Trees with pine wilt should be removed to the ground line or deeper. Wood should not be saved for firewood. It can be chipped for mulch, although it should be composted for a few months or spread out to dry before using around pines.

Austrian pines are also showing problems. They have long (3-5 inch) stiff needles held in bundles of two. Austrian pines can suffer from a tip blight known as Sphaeropsis (formerly diplodia).

The fungus attacks young needles causing browning, stunting, and twisting of new shoots and needles. Lower part or one side of a tree may be the first area affected. During wet springs, every branch may have brown tips. Infected stems often result in droopy candles (new growth). White resinous cankers may appear on stems and older branches. Dead needles may stick to stems.

Control of Sphaeropsis tip blight is not easy and requires that all affected twigs, needles and cones be removed. If the disease is caught early, sanitation can be effective; however, severely infected trees are difficult to manage. Austrians may live with the unsightly disease for years. Fertilize trees to stimulate vigorous growth. Fungicide sprays containing propiconazole or thiophanate-methyl are recommended in conjunction with cultural controls. Three sprays are necessary: one at bud break, half candle elongation, and full candle elongation.

White pines are also common in the landscape with their long soft needles held in bundles of five. Typically they don't suffer from insects or diseases; however we are seeing white pine death that does not appear to be infectious. Sick white pines are most likely suffering from white pine decline which involves many stress factors working together to cause tree decline and often tree death. Sick white pine trees have often been planted in clay soils or in windy sites such as new housing developments. Planting too deep or extremes in temperature or moisture may also contribute to root injury.

For more information on evergreen insects and diseases

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