Cedar apple rust infects hawthorns

Hawthorns with a 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 planting this plant if you have hawthorns in your garden.

As with crabapples, spraying now will not help your trees, since chemical controls must be applied in spring to prevent this disease.

• Crabgrass may be evident in your lawn now (it has a lighter green color and wider leaf blade than bluegrass), especially if it has been neglected. This annual weedy grass seeds readily in the fall. Keep it closely cut to prevent seed formation or pull it out by hand. There are herbicides that will control crabgrass at this time of year but they will not be as effective after the crabgrass has set seed. Make note of bad areas in your lawn and apply a pre-emergent herbicide that prevents weed seeds from germinating in early spring before lilacs flower.

• Holes in the lawn dug by raccoons and skunks may indicate the presence of grubs, which feed on grass roots. The adults prefer to lay eggs in moist lawns, so if you irrigate your lawn in a neighborhood where others do not, you may have a greater chance of having grubs in a dry year. There was a lot of rain this year, creating more opportunities for egg laying.

Check areas of the lawn that are browning or where the grass lifts like a piece of sod. Bent grass (a weed in a bluegrass lawn) is now turning brown in lawns because of cultural problems other than grubs, so be sure to check to make sure grubs are present.

If there are more than 12 grubs per square foot and you are seeing extensive damage, 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. Follow the instructions for application.

• As you are weeding in the garden, be sure to look at any shrub plantings or hedges to see if there are weedy trees present. Box elder, mulberry, Siberian elm and buckthorn trees will seed into the centers of shrubs and start growing. They can be hard to spot early on without a closer look. They are easier to remove when they are small.

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