The Homeowners Column

The Homeowners Column

In September a flurry of flight may greet plant huggers

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator

Summer weather lingered long and lazy into September. We may yearn for the cooler weather of autumn; however, many insects are perfectly happy with heat. Here in September a flurry of flight may greet plant huggers.

According to Dr. Phil Nixon in the recent issue of UI Extension's Home, Yard and Garden Pest Newsletter, whiteflies are a common sight in the landscape, feeding on the leaves of many flowers, shrubs, and trees. Tomatoes and the weedy velvetleaf, also known as buttonweed, are commonly infested. As their whitefly name implies they are 1/16-inch-long insects with white, powdery wings. They sit on leaf undersides and fly short distances when infested foliage is disturbed. They suck plant sap which can cause leaf distortion. Generally, late season whiteflies can be ignored, their feeding is too late to cause serious damage to plant health or even cause obvious aesthetic damage.

In greenhouses whiteflies can cause serious problems. However, outdoors we have the natural leaf drop and cooler temperatures of autumn working in our favor. Whiteflies are not particularly strong fliers so a heavy stream of water on the undersides of leaves may be enough to lower their populations and at least make us feel better that we are doing something to curb their conduct. If more management is required, insecticidal soap or neem oil provides some control of whiteflies.

Potato leafhoppers are another minuscule insect that flees with flight when you brush against landscape plants or their tiny dead bodies often litter indoor light fixtures. Dr. Nixon reports these tiny insects and their damage have become obvious during recent weeks. Potato leafhoppers attack oak, maple, red mulberry, red bud, cottonwood, birch, apple, dogwood, hawthorn, wafer ash, euonymus, black locust, and cherry.

Red maple is most severely damaged. The expanding leaves at branch tips are curled and stunted, and they are mottled with light green, red, and brown. Leaf edges and entire leaves may turn brown or black. Stem growth is greatly reduced. Overall, the damage looks similar to the 2,4-D herbicide injury and potato leafhopper damage may be frequently misdiagnosed as herbicide injury. Leafhopper damage this fall is heaviest at the top of the tree rather than on side branches. On other host species, leaves may be misshapen, have brown areas, show early fall color, or have stippling (light dots).

Potato leafhopper adults are wedge-shaped, green, and about 1/8 inch long. They fly readily from foliage when approached and are very migratory, making it difficult to find the insects on damaged foliage. They are strongly attracted to lights at night and are small enough to go through the mesh of window screening. Leafhoppers are the annoying little green bugs that fly indoors around the newspaper or book you are trying to read during summer evenings.

This late in the growing season treatment for leafhoppers is probably not warranted. These insects start feeding in May in Illinois, and treatment at that time to prevent leaf damage and reduced growth through the growing season may be necessary.

So the morals of the story: insects often travel in herds; insects compensate for their tininess by being numerous; don't breathe too deeply when hugging landscape plants or numerous tiny insects may go up your nose; and check the calendar when deciding if insect control is warranted.

Join Master Naturalists for "Discover Illinois – Exploring Nature" on Monday September 23, 2013 from 6:30-8:00 PM at the U of I Extension auditorium 801 North Country Fair Drive in Champaign presented by Susan Post, author and retired field biologist with Illinois Natural History Survey, who along with her husband Michael Jeffords, has been hiking, exploring, and photographing Illinois for over 30 years. For more information PH: 217-333-7672

Volunteer for National Public Lands Day September 28, 2013

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