Look out for beneficial hornets as you garden; they sting if disturbed

Bald-faced hornets construct large paper nests in trees and large shrubs at head height and above, so be sure to look in tree canopies as you are working in the garden. Paper wasps build nests under eaves, signs and fence railings and will sting if disturbed. All these are beneficial insects, so control them only if they pose a safety hazard.

What to do now for fungal disease

Some crabapples are very susceptible to apple scab, a fungal disease, and those that were not treated in spring may have lost many of their leaves. Their remaining leaves can be affected with black and yellow spots. The wet weather last spring was conducive to this disease, so it is prevalent this year.

Spraying now will not help combat this disease, but you can give the trees extra care with supplemental watering as needed for the remainder of this year and fertilizing in fall or next spring.

Remove all infected leaves and do not add them to your compost pile. Most home compost piles do not heat up enough to kill disease organisms. Also, consider replacing disease-prone trees with a cultivar that is disease resistant.

Hawthorns with a more severe case of cedar apple rust may have foliage that turns bright yellow and drops prematurely. Small yellow spots will appear on leaves after infection in spring. This disease requires eastern red cedar (Juniperus virginiana) as an alternate host, so avoid this plant if you have hawthorns in your garden. As with crabapples, spraying now will not help your trees, since controls need to be applied in spring to prevent this disease.

Check for grub damage

Holes in the lawn dug by raccoons and skunks may indicate the presence of grubs, which feed on grass roots. Check for areas of the lawn that are browning or where the grass lifts like a piece of sod. If there are more than 12 grubs per square foot and you are seeing extensive damage, you may want to use a product designed for quick kill of the grubs. Be sure to read the bag carefully to ensure that you are buying the right chemical for grub control at this time of year. It is important to follow the instructions for application.

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