Top Ten Tree Problems

1. Two-Lined Chestnut Borer

TLCB, Agrilus bilineatus, is an opportunistic insect that attacks weakened oak trees; red oak being its preferred host. Best management is prevention, proper watering, avoid soil compaction, mulch for moisture and to prevent bark damage.

2. European Sawfly

ESF love your pine trees; larvae feed on one or two-year-old pine needles. Usually, sawfly populations are kept low by natural enemies. If infested, remove the larvae colonies; pesticide application may be needed.

3. Verticillium Wilt

VW is caused by soil-borne fungi. In Minnesota, ash, catalpa and maple are frequently infested. Leaf curling, drying, and dieback of shoots and branches are signs of VW. Water, soil fumigants, mulch, and fertilize. Remember, the fungi is in the soil, so if the tree dies, get a VW resistant tree or shrub. My favorites: Ginkgo, Hackberry, Hickory, Larch.

4. Borers

Borers are attracted to unhealthy trees, burrowing in and laying eggs inside the trunk. The best defense against borers is to keep your trees healthy and unstressed. Birch looking unhealthy, look for D-shaped exit holes. Water, mulch, fertilize, prune in winter.

5. Hemlock Woolly Adelgid

One of the most common pests, these insects can cause the death of a tree if left untreated. They leave behind a telltale white wax and target primarily older trees.

6. Scale Insects

These insects target primarily hardwoods and conifers. Some signs of an infestation include abnormal leaf and shoot growth, yellow or red leaves, and branch gouting.

7. Anthracnose Disease

This fungal disease affects deciduous and flowering trees. Look for a spotting of foliage in spring and summer.

8. Winter Injury

Even during mild winters, evergreens can lose moisture and not be able to replenish it. Thus, make sure your evergreens have sufficient soil moisture.

9. Black Knot

Cherry tree have coal-like swelling? Cut off all shoots and branches bearing black knot. Should be pruned out over winter 8" below the knot. Should be monitored on a daily basis by homeowner.

10. Aphid Insects

Aphids are small and pearl shaped. An infestation can cause yellow discoloration and defoliation.