Master gardeners: Control aphid population with these tips

Developing the habit of scouting for insects in your landscape has benefits. Potential problems will be seen earlier rather than later when they can be more severe.

As you scout, keep in mind that there are good guy and bad guy insects and those that fall somewhere in between. Identifying insects is foremost to determining if they are actually harming a plant. The use of chemicals should be your last resort.

Consider the tiny, soft bodied, pear-shaped aphids for a discussion of chemical versus nonchemical treatment. They are on every list as a bad guy insect. Host plants for aphids include a variety of perennials, annuals, vegetables, trees even houseplants, and the insect comes in a multitude of colors.

These amazingly complex insects have a straw-like mouth part that allows them to pierce the succulent new growth at the tip of plants and suck out some of the juices. When the number of aphids is high, damage can cause a distortion of the plant tip or leaves and even stunted growth. Trees typically sustain cosmetic damage.

Honeydew is the clear, shiny and sticky waste product of aphids that is found where they are feeding. It can be seen on plant leaves, lawn furniture, pavement and even cars parked under infested trees. Ants are attracted to honeydew’s sweetness and their presence can be a sign that aphids are near. A fungus, black, sooty mold, can grow on honeydew wherever it is found. On plants, this can cause further disfigurement and restrict photosynthesis.

Regular scouting of the garden for insects or changes in plants should reveal an aphid population before it gets large.

When found, the first line of defense is your garden hose and a strong spray of water to dislodge as many aphids as possible. If this doesn’t yield the desired result, insecticidal soap may be applied directly onto the aphids. This leaves no lasting residue and is virtually nontoxic to animals, birds and beneficial insects — the good guys. Vegetables can be sprayed up to harvest — always follow label directions.

Encourage natural aphid predator good guys to your garden. This requires a balancing act of sorts, because to come and stay in your garden, they will require food, such as aphids. Visit our website and search “attracting beneficial insects” to learn more.

Email your home garden and lawn questions to uiemg-dupage@illinois.edu or phone the Master Gardener Helpline at 630-955-1123. Visit our website at http://web.extension.illinois.edu/dkk/.

Julie Moore has been a master gardener volunteer with the University of Illinois Extension in DuPage County for 10 years and has a degree in ornamental horticulture from the University of Illinois.

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