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How Can I Get Rid of Aphid Honeydew?

Aphids on maple tree leaves

Aphid ‘spitting’ has many options for treatment

If you’ve noticed a greenish-yellow residue on your plants or yard around late May or early June, you may have wondered where it comes from. Aphid “honeydew” is a substance excreted by aphids in late spring, and found on tree and plant leaves, as well as surfaces below trees and plants.

It’s not quite as gross as it sounds: aphids’ diet is entirely plant sap, so the substance you may find on your leaves, deck, barbecue, or car isn’t much different from regular sap. Certain species of ash, beech, cedar, chestnut, elm, fir, hickory, maple, oak, pine, poplar, spruce, and willow trees produce sap that feeds aphids. A few other plants, including currants, grapes, and sunflowers, also produce this sap.

To get rid of aphid honeydew, you’ll need to get rid of the aphids. Fortunately, there are many effective treatments to remove aphids on plants. For trees, certified arborists and plant healthcare workers in Ontario can offer effective professional insecticidal treatments for your trees. Some other treatments can supplement these and be done either by a professional, or by homeowners and residents.

Aphids in Ontario

Green aphids on a twig

Small numbers of aphids are common in yards and gardens. As long as they remain few in number, they won’t cause problems; it’s when they establish large colonies that they can cause serious damage. Honeydew iteself does not hurt plants, but damage from the aphids can weaken the plant — along with the annoying mess caused by aphid honeydew.

Southern Ontario’s aphids tend to appear in late spring each year, usually late May to early or mid-June, and they stick around all summer.

Green peach aphids and potato aphids are the most common aphid types in Southern Ontario, both small and yellow-green in colour. You’ll commonly find them on the undersides of leaves.

Woolly Aphids

Woolly aphids have a very different appearance. If you’ve noticed something that looks like bits of cotton or white mould along branches, twigs or leaves of trees, you may have a woolly aphid problem. These hairy insects are covered in white fuzz.

Honeydew from woolly aphids can turn into a black fungus that looks like soot. This fungus is unattractive, and if it spreads widely over a tree, it can start to block sunlight from getting to the trunk and branches.

Aphid Treatment for Trees

A certified arborist or pest management professional can offer an insecticidal treatment to your trees to control a large aphid infestation. In Ontario, insecticidal treatments like this can only be administered by licensed professionals.

Vista Tree offers aphid treatment with ACECAPS, a systemic insecticide inserted into a tree by drilling a hole then hammering in a cap of the insecticide. This treatment should be done in springtime, when leaves on trees have come out and before an infestation is in full peak during the summer months.

This treatment is ideal for aphid honeydew in large trees, where spraying the full tree is impractical or impossible. The caps are placed at intervals through the tree and the insecticide will work itself through the interior of the tree, killing aphids and several other destructive insects. Protection lasts for between 12 and 18 weeks, depending on the scale of the infestation.

ACECAPS are not suitable for fruit trees or any trees where nuts or sap are consumed.

Live Ladybugs for Aphids

Two ladybugs and a green aphid on a plant

What eats aphids? If you’re a gardener, you may be familiar with this treatment. Ladybugs are a natural predator of aphids. Live ladybugs lay eggs on your aphid-infested plants, and the resulting larvae will eat aphids.

Boxes of hundreds or thousands of dormant ladybugs can be purchased from some garden centres and big box or hardware stores in the summer each year, normally through late June in the GTA and Southern Ontario, though the exact shipping dates will vary based on the weather forecast. If it’s too hot, over 30°C, you should wait for cooler weather.

Ladybugs are kept in the fridge until you’re ready to release them.You should release ladybugs at dusk or in the early evening, as they will fly away in the heat of the daytime. Release them into a garden bed, watering the area first. Spacing out the release of a package over a few days will give the best results.

Insecticidal Soap and Prevention for Next Season

Insecticidal soap, such as Safer’s Insecticidal Soap, is a safe product for treatment on plants (including edible plants like cucumbers and tomatoes). Safer’s and similar products are made from potassium salts and safe for the general public to use. They contain no synthetic chemicals and work as a contact poison on soft-bodied insects like aphids.

To supplement a treatment like ACECAPS, you can spray insecticidal soap regularly on your plants through the summer, making sure you coat both the top and bottom of leaves. Avoid spraying in very hot weather over 32°C.

Regular use of organic fertilizer in your garden also helps to control nitrogen levels, which will help keep aphids out.

Honeydew Cleanup

Since aphid honeydew is essentially just sugar from trees, aphid honeydew removal is safe and easy. You can use a hose, or water with a couple tablespoons of vinegar mixed in, to wash it off surfaces like patios, outdoor furniture, playscapes, or vehicles. A soft cloth or scrub brush can be used for cleaning, depending on the surface.

 

It’s the right time of year to be thinking about aphid treatments for your trees! For assistance with aphid removal and insecticide treatment, contact Vista Tree to find out about your treatment options.

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