CONTROLLING DIPLODIA TIP BLIGHT IN BLOOMFIELD HILLS

Diplodia tip blight is a very common fungal disease on pines in Bloomfield Hills. Austrian pine, mugo pine, and Scots (scotch) pine are the pine species most commonly infected with Diplodia tip blight.

Typical symptoms of Diplodia tip blight include dieback of the growing tips - hence the disease name. The fruiting bodies of Diplodia tip blight can easily be observed since they appear as pepper sprinkled over the surface of woody tissue. During a severe outbreak of Diplodia tip blight, a high percentage of the tips of a particular tree may be affected and will give the tree a brownish cast. Expanding buds, elongating candles or entire branches may be affected. Occasionally, only needles will be blighted. Affected needles remain on the tree, and in some instances entire trees may be killed. Diplodia tip blight can be confused with other problems such as the European pine shoot tip moth.

Diplodia tip blight fungus overwinters as maturing reproductive structures on cones, dead needles, or the needle sheath. Reproductive structures release millions of spores which may be splashed to emerging growth and cause infection. Two year old cone scales are an efficient source of fungus spores for infection. This is why mature pine trees (20 plus years) with abundant cones are most severely affected.

Controlling Diplodia tip blight without chemical fungicides is virtually impossible. A proper planting site and reduction of stress can reduce the severity of Diplodia tip blight. Pine trees infected with Diplodia tip blight should be periodically fertilized to maintain their health. Pruning infected pine trees will help the appearance of the tree but will not reduce Diplodia tip blight activity to any significant extent.

Fungicide applications are necessary to reduce the level of Diplodia tip blight activity. The first application should be made just before or during bud swell. This time will vary from year to year, and with the pine species, but is usually around mid-April in Bloomfield Hills. A minimum of two fungicide treatments should be applied, but better control of Diplodia tip blight will be obtained with a third fungicide treatment.