Delbert Johnson Doctor of Stumpology

CYTOSPORA CANKER OF SPRUCE

Each year many beautiful ornamental spruce trees are attacked by the destructive disease, Cytospora canker. The cause of the canker is the fungus, Cytospora kunzei, considered to be a weak parasite because it primarily attacks trees which have been stressed.

STRESS FACTORS- Among these conditions which weaken the spruce are drought, low fertility, mechanical injury, insect feeding (such as by the spruce mite), or trees growing in poor soil. Trees affected by any of these are more likely to be infected than those which are vigorous and healthy. Thus, cankers are generally found on trees over 15 years of age. White patches of pitch or resin are found on HOSTS-Besides the spruce, Cytospora canker infected branches. has also been reported on larch and hemlock.

SYMPTOMS - WHAT TO LOOK FOR- Infection commonly starts on the lower limbs and gradually works up the tree, limb by limb. The first noticeable symptom is that one or two lower branches become off-color. Needles, instead of being dark green in color, turn a dull yellowish-green and then brown. Soon needle drop occurs leaving bare ends on the branches.

Copious amounts of resin or pitch are produced in the cankered area and this may drip down to lower branches. The canker restricts normal water movement to the needles beyond the infection; therefore, they dry out and turn brown.

HOW IT SPREADS-Spores produced in the cankered area are most commonly spread by wind-driven rain. Insects and birds are other likely carriers.

RECOMMENDATIONS- Disease spreads upward from lower 1) Fertilize to keep the tree as vigorous as branches, causing trees to become unsightly possible. 2) Water, especially during for many years before they die. drought periods. 3) Spray to control insect feeding. No fungicides are currently effective against this disease. 4) Prune, removing all infected branches.