Austrian (Pinus nigra) and Scotch (Pinus sylvestris) pines have been planted widely throughout the Midwest for decades. Mugo (Pinus mugo) pines have been frequently used in home landscapes.

In recent years, these trees have been suffering severely from a "tip blight" caused by the fungus, Diplodia pinea (also known as Sphaeropsis sapinea). Since so many of these non-native species have been planted, the problem has now reached "epidemic proportions" since the trees are reaching a mature stage where they are very susceptible to the disease.

Red pines are less susceptible unless planted in dense stands where air movement is limited. White pines are virtually immune to the disease.

The fungus over-winters on dead needles, bark and cones. In the spring, rain spreads the spores to swollen buds and emerging shoots. Toward late June to July, infected needles on the tips of the branches turn brown.

Over years, the disease progresses and kills more of the new growth each year. In time, entire branches die and the tree itself loses vigor.

As with all fungal diseases, diplodia tip blight is encouraged by keeping plant tissue moist for long periods of time. So, trees that are given enough room to grow properly may be bothered less because they have good air flow around the plant. This allows needles to dry off more rapidly after rain.

Another way to help prevent the disease is to keep the tree otherwise as healthy and vigorous as possible. Avoid water stress, insect infestations, mechanical damage or other stresses.

In some instances, it helps to prune off and destroy the first twigs that are infested. Be sure to prune when the needles are dry to avoid spreading the spores from branch to branch. You can also try to knock off infected needles and thoroughly rake them off the ground near the tree.

There are no known biological controls. Cultural management by pruning infected branches and maintaining good vigor by proper fertilizing and watering will help aesthetically but will not cure the plant.

Currently, the only effective control is a fungicide treatment. While there are several fungicides labeled for use on Diplodia, the benzimidazole class tend to work best.

Bordeaux mix is also effective. It may be abrasive to spray equipment but people have reported good results.

The timing of applications is absolutely critical! Sprays should be applied according to label rates at or slightly before bud break. Failure to protect the swollen buds and emerging shoots during the rainy infection period could lead to severe shoot loss and make subsequent treatments useless.

Depending on the weather, species of tree and genetic variability, the optimum time for the first spray may vary from early April to early May. For high value trees, three to four applications at 10 to 14 day intervals may be needed to provide good control.

It is better to get the first spray on a little early than to be a little late. Low value trees may be helped by as few as two sprays.

Patience Is a Virtue: Severely infected trees have been brought back to good health with sufficient effort and patience. However, it may take several years of spraying and quality maintenance to show results.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


 

New Plantings: The best approach to avoiding future problems is to plant resistant types of pines. Native species have far fewer problems than exotics such as Austrian and Scotch pines. Red pine is somewhat less susceptible and the white pine is practically immune.

Whatever you plant, be sure to leave plenty of room for the mature size of the tree. Crowding is a major factor in severity of diseases in later years. If you need a dense planting, put the young trees close together but be sure to thin them out over the years to allow for proper spacing and air circulation.

Some pines susceptible to diplodla tip blight:

 

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