Pine trees have long been a staple of the landscape for their ability to provide year round interest and screening. In recent years pines have fallen victim to several problems. These problems have reached epidemic portions and for that reason Johnson County K-State Extension no longer recommends that either Austrian or Scotch pine be planted.
In order to protect existing pines in the landscape it is recommended to properly diagnose the problem and take action. Following is a brief outline of the pine problems currently affecting trees.
Spaeropsis (Diplodia) Tip Blight
Tip blight attacks mostly Austrian, but can also damage Scots (Scotch) and Mugo pines in the spring when growth starts in late April and May. Spores of the disease travel through the air landing on damp pine needles that are just emerging from what is called the candle stage. The new shoots are highly susceptible to the disease. Later in the season, late May or June, the new shoots die. Repeated attacks eventually kill the lower branches of the pine. Overtime the tree becomes unsightly and eventually dies.
Symptoms of the disease cause the needles to not fully elongate and turn brown. They tend to hang on the tree for several seasons as the severity of the disease increases. This problem has been around for 20 to 30 years but is more severe in years when there is a wet spring.
Tip blight can be controlled, but it takes yearly fungicide applications applied throughout late April and into May. Unfortunately, this disease is favored by rainy weather so fungicide applications can easily be washed off the tree, reducing the effectiveness of control such as the case this year.
Pine wilt is mainly a problem with Scots pine, but others can be susceptible. This problem is not insect or disease-related but caused by another pathogen called a nematode. The nematode is moved from tree to tree by an insect called the Pine Sawyer Beetle. Control of this insect is not practical, and as a result, control the nematode is extremely difficult.
Once nematodes are introduced into a healthy Scots pine, they rapidly multiply, and plug the vascular system of the tree resulting in death. The classic symptom of this problem is a maturing Scots pine that dies in a matter of a few weeks or a couple of months. This is a complete death of the tree, not just random branches. The death normally appears in the late summer or fall.
Unlike tip blight, diagnosing wilt is more difficult. Educated guesses can be made about the possibility of pine wilt if all the clues fit together. However, a culture must be made in the lab to detect nematodes. At this time there are no reliable and practical controls. Affected trees must be removed.
Pines are not a native species to the Johnson County area. Pines do not grow well in the moisture and temperature extremes we experience. Drought conditions or excess moisture result in a decline of the root system and dieback in the tree. Stress damage is often seen as random dieback, or maybe even the top of the tree declining. This pattern is completely different from that of pine wilt and not typical of the tip blight pattern as it is not always on the lowest limbs.
Control strategies would be preventive in nature. That is, to provide even moisture during dry spells to reduce stress and keep the tree in a healthier state. A healthy tree is also the best defense against the other problems.
What to do?
The most important step is to determine the correct problem and take action from that point. A good rule of thumb to follow when dealing with pine issues is to remember this saying. “If it is brown, cut it down.” Sanitation is needed for the prevention of pine ailments. Removal of infected limbs with tip blight reduces the spread of the disease. Pine wilt infected trees should be cut down as soon as they die or by late winter to reduce the spread of the nematodes.
Johnson County K-State Extension is available to assist with pine problem diagnoses. Samples may be brought to the office for diagnoses. E-mailing photographs of the ailing pines may help to identify the issue. Contact the office by e-mailing email@example.com or (913) 715-7000 for more information.