Proper pruning practices and pest control can keep your garden healthy

Pruning is my favorite gardening task, and now is a suitable time to start pruning shrubs that have put on growth and need shaping.

Prune them as needed to keep them at the proper scale for your garden. The shrub’s growth for the season stops in early to mid-July, so there should be minimal new growth later in the season if you prune now.

Try using hand pruners instead of an electric hedge clipper to create a more natural look by making individual pruning cuts at different heights throughout the shrubs. For a more formal look, make cuts at the same height. Prune right above the leaves to help hide the cuts. Careful pruning will leave the plants smaller but not looking “sheared.” Remove dead wood when you see it.

Apple scab and magnolia scale

There are varieties of crabapples that are susceptible to a fungal disease called apple scab, and those not treated in spring may be losing their leaves during the summer. The disease starts in early spring and appears as black and yellow spots on the leaves. Severely infected leaves fall off the tree. Spraying fungicide at this point will not help the tree as it must be applied in early spring to prevent the disease from occurring. Give the affected tree extra care by providing supplemental water as needed and fertilizing in the fall or next spring. Consider replacing disease-prone trees with resistant varieties in the future.

Magnolia scale was a significant problem last year. This is the time to check for magnolia scale, which is an insect about the size of a pencil eraser. Typically found on the underside of magnolia branches, the scale is responsible for creating an overall thin condition on the tree. The scale exudes a clear, sticky honeydew after feeding on the plant.

Black sooty mold is a fungus that grows on honeydew. Gardeners often notice the black mold on or under the magnolia before noticing the actual scale. The mold itself is not the real problem. On small trees, simply pick off the scale and squash them. Other control measures include spraying with summer-weight oil or applying an insecticide when the scale is in the active crawler stage, generally in early September.

For trees with a history of magnolia scale, a late-winter to early-spring application of dormant oil will provide good control for the scale. If your magnolia is infested with scale, provide extra water during summer to minimize stress.

• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.