Harmful magnolia scale secretes sticky honeydew
This is the time of year to check closely for magnolia scale, 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 the honeydew. Gardeners often notice the black mold on or under the magnolia before noticing the actual scale. The mold itself is not a real problem but a sign that there is an insect such as magnolia scale.
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 tree is affected, provide extra water during summer to minimize stress.
• Established bluegrass lawns need an inch of water a week to continue to actively grow and stay green throughout the summer. Water deeply once a week rather than lightly multiple times a week. This promotes a deeper root system so the grass will hold up better to stress.
To determine how long it takes your sprinkler to deliver one inch of water, set out a coffee tin, tuna can or other shallow can with straight sides and time how long it takes to fill with an inch of water. Be consistent with your watering practices - either water on a regular basis all summer or let your grass go dormant during hot, dry periods.
If your soils are heavy and long periods of watering start to cause runoff, you may need to split watering into a couple times per week.
The consistent rain and generally cooler temperature have kept lawns green and growing through June. Mowing your lawn at a height of 3 inches or more will also help the grass withstand stress and keep out weeds.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.