Crabapple trees highly susceptible to scab disease

Some crabapples are very susceptible to apple scab, and those not treated in spring may have lost many of their leaves. Their remaining leaves can be affected with black and yellow spots.

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

Remove all infected leaves and do not add them to your compost pile.

Also, consider replacing disease-prone trees with a cultivar that is resistant.

Many crabapples are also showing signs of stress with thin foliage and dead wood. Prune out dead branches now and provide supplemental water during dry periods to help reduce stress on the tree. Be sure the branches are dead before pruning, as branches that have defoliated due to disease will likely leaf back out next year.

• 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, then you may consider using a product designed for quick kill of the grubs. Be sure to read the bag carefully to ensure you are buying the right chemical for grub control at this time of year. It is important to follow the instructions for application.

• Look for woody plant weeds like mulberries, buckthorn and boxelders that grow up in the middle of shrubs and in hedges. These weeds tend to be hard to spot when they are young and are more difficult to eradicate as they get bigger.

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