How to Control Aphids on Linden Trees
Linden (Tilia spp.) is an excellent shade tree that can provide much needed relief on a hot, summer day. Unfortunately, linden can be infected with insects, particularly the linden aphid (Eucallipterus tiliae). Aphids secrete sap from plants. If left uncontrolled, they can severely damage or kill plants, even a plant as large as a linden tree. However, early detection ensures greater success at keeping the pests under control and limiting damage to your linden tree.
Inspect your linden tree frequently to check for aphids and aphid eggs. Examine several leaves from different areas of the tree and look on both sides for aphids or the sticky residue called honeydew that they leave behind. Aphids are more prevalent during mild weather, when temperatures are between 65 and 80 degrees Fahrenheit and the tree is actively growing. At this time, check the tree for aphids at least two times a week.
Avoid using pesticides in your landscape that kill aphids’ natural predators, such as lacewings, lady beetles and parasitic wasps. Add natural predators, which can be purchased online and at many nurseries, to the area. You must release enough -- sometimes over 3,000 for a medium size tree with a heavy infestation -- for this method to be effective. Release the lady beetles in the early evening and release another set of bugs of the same quantity one week later.
Look for ants crawling up the linden tree; they are a sign of aphids and help them survive by keeping the aphids' natural enemies at bay. If necessary, wrap the tree with a sticky band made for this purpose or with duct tape, sticky-side facing out. You can also use ant baits or stakes around your tree. These do not hurt aphids’ natural predators, according to University of California's Integrated Pest Management Program website.
Remove aphids and eggs with the hard spray from a hose; most will not be able to return to the tree. Spray in the morning so your tree can dry out before nightfall. Repeat as often as necessary. This works best for a smaller, younger linden trees that you can easily spray from top to bottom.
Spray an insecticidal soap or horticultural oil, which kill some aphids without killing their natural predators. They are also safer around children and pets, but are not as effective as an insecticide. Therefore, for a large aphid infestation, use an insecticide, such as permethrin or malathion, which will kill most of the aphids. Apply soaps, oil and insecticides directly on the aphids per manufacturer directions.
- University of California Agriculture and Natural Resources Integrated Pest Management Program: Aphids
- University of California Agriculture and Natural Resources: Lady Beetle Releases for Aphid Control -- How to Help Them Work
- University of California Agriculture and Natural Resources: Linden
- Sunset: Tilia
Melissa Lewis is a former elementary classroom teacher and media specialist. She has also written for various online publications. Lewis holds a Bachelor of Arts in psychology from the University of Maryland Baltimore County.