Problems of Pine Trees

Perhaps the major concern when planting pines, in particular large plantings, is pine wilt disease, caused by the pinewood nematode. Austrian, Red, and Scots pine are most susceptible to this problem. White pine is not considered susceptible to pine wilt. If making a large planting, include a variety of pines, spruces, and fir to help avoid major problems with insects or disease.

White Pines, especially in the Mid-west, can suffer and even die from a relatively new disease called White Pine Decline. Affected white pines show various symptoms of decline or dieback. Sometimes trees appear healthy for a decade or more before decline symptoms are noticed. Other pine species don't appear affected by the disorder. See the problems section below for more information.

Below is a general summary of the most common problems occurring to most species of pine tree.

Needles fall off tree in large numbers

Normal behavior - On White Pines, do not mistake annual needle drop for white pine decline. It is normal for conifers to drop their oldest needles in the fall. This annual shedding occurs on all trees at about the same time, and always occurs in the fall. An abnormal needle drop would occur in the spring or summer, affecting only one or a few trees, rather than all or most of them.

White Pine needles die in the spring

Injury from de-icing salt also causes the death of white pine needles and branches. Symptoms from salt show up on the side of the tree closest to the salted road. Trees closest to the road are most severely injured.

Needles Flecked; Red-brown;

Drop Spider Mite - One of the most damaging pests of conifers are spruce spider mites. They resemble miniature spiders no larger than the head of a pin and may be black or green. Often you can spot their fine webbing among the needles and twigs. Starting with the lower branches, they suck sap from the undersides of aging needles causing a stippling effect. The infested needles eventually turn reddish-brown, and drop off, severely disfiguring a pine tree. Mites usually attack trees that are stressed for some reason, perhaps by drought or lack of enough sun. Sometimes overuse of broad spectrum pesticides in the yard that kill off resident beneficial insects promote a mite population explosion.

The presence of spittle masses on twigs of pine in May and June is indicative of the pine spittlebug.
Pine spittlebug will feed on Scots, Austrian, and White Pines; along with spruces and firs. Nymphs of pine spittlebug are brown. Heavy populations may be more of a serious problem, as sap flow can be reduced.

Sticky Bud Tips; Needles Turn Yellow

Pine Shoot Beetle -Originally discovered in a Christmas tree plantation in Ohio, these pests have spread through the Midwest and into Pennsylvania, New York and Ontario. Beetles are larvae of reddish brown moths that hibernate in bud tips of pines. Their presence is betrayed by masses of pine pitch on the infested buds. When the weather warms they emerge to infiltrate healthy buds on the newly developing shoots. These grow only 1 or 2 inches before they become distorted and die. Then the adult moths emerge to lay eggs for the next generation on twig tips, bark and needle sheaths. When these eggs hatch, new beetles bore through the base of the needles, causing them to yellow and die.

There is no really reliable treatment for this problem except to prune out and burn any infested, sticky buds as soon as you spot them to prevent the moths from emerging. In large trees, hire a certified arborist to do this. Buy nursery stock that is guaranteed to be free of this pest.

On White Pines, declining trees usually look a paler green, or even yellowish, compared to healthy trees. Needles often are shorter than normal; sometimes the tips of needles turn brown. Needles from the previous season often drop prematurely, giving the tree a tufted appearance.

Pine Decline - A variety of environmental stresses combine to produce this physiological disease. They include: poor location (soil alkaline instead of acid, heavy clay soil, crowding), salt used for winter de-icing, heat and drought. Unless these problems are identified and corrected promptly, white pines lose color in their needles and experience premature needle drop and stunted growth. Eventually the tree may die.

Needles; Branches Encrusted; Growth Stunted

Scale - Scale insects sometimes feed on pine needles, protected beneath distinctive, rounded waxy shells. These shells may be white, yellow or brown to black and are about 1/10 to 2/5 inch in diameter. They appear as bumps along the twigs and needles of pine trees. Severe scale infestations cause pine needles to turn white or yellow. Cottony masses appear on undersides of branches, especially where they join twigs or other branches. Severe infestations can kill young trees.

Yellowish Needles; Tunnels In Bark

Pine Bark Beetles - Adult pine bark beetles are short-legged, stout and about 1/8 inch long. The young beetles are soft and yellow in color, but soon turn dull brown. These pests are especially dangerous after a prolonged drought. Beetles of an overwintering brood attack the pine trees in the spring, starting at midtrunk, working both up and down. Opportunists, they are attracted to trees already weakened by injury or other stress. Their larvae, or grubs, bore through the outer bark and excavate S-shaped tunnels in the sapwood. Emerging adult beetles leave tiny telltale holes in the bark. Affected trees show yellowish-green foliage from 10 to 14 days after an attack. By the time the top of the tree turns reddish the beetles have usually left, except in the winter months. No effective controls are available. Keep trees in vigorous health by proper feeding and watering. Cut down and destroy severely infested trees.

Needles Wilt; Cankers On Trunk;

Blister Rust - Blister rust is a fungal disease that produces ugly swellings filled with powdery orange-yellow spores on trunks and branches of white pine and other 5 needle pines. In spring the rust spores are dispersed by wind, and if they land on nearby currant or gooseberry bushes, they infect these plants to complete their life cycle. In the fall these infected secondary host plants produce a second type of spore that infects pine needles and causes them to wilt and turn brown. Eventually the fungus grows into the branches and trunk, and after several years may girdle and kill the tree. Control this disease by eliminating all currants (especially black currants) and gooseberries from within 1,000 feet of susceptible trees. Treat moderately infected pines by carefully cutting away canker tissue. If the tree is nearly girdled, cut it down and destroy it.

Needles Discolored; Drop Prematurely

Needle Cast - This fungal disease causes needles to turn yellow, then shrivel and drop off. Infected needles show black spore-bearing bodies on their undersides. Smaller trees may be defoliated. Collect and destroy fallen needles in late fall or winter to eliminate overwintering disease spore.

Bark Of Trunk and Roots Gnawed

Rodents - Small rodents such as mice and voles sometimes gnaw bark off trunks and roots, causing injury that allows disease organisms to invade pine trees. Keep the area around the trunk free of weeds and grass and delay spreading winter mulch until after the ground freezes so rodents are not able to nest near the trunk. If you have chronic problems with rodents wrap pine tree trunks with guards of 1/4 inch hardware cloth or commercial tree guards to repel the pests.

Foliage Eaten; Bark Is Damaged In Flat Strips

Deer - Deer damage pine trees by eating their needles and by rubbing against their trunks to remove the fuzz from their antlers. The occasional deer visitor may be discouraged by a repellent product sprayed on the trunk and lower branches of the tree. This will have to be renewed after it rains. If your yard is regularly visited by a local deer herd it may be necessary to fence the area where the white pines are located with a simple electrified wire. If lots of your plants are being eaten, the best solution is to fence the entire yard with relatively inconspicuous black poly netting deer fencing.


Infographic: Problems of Pine Trees


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