Decide if It's Necessary
First, ask yourself if the impact they cause warrants getting rid of them. If there is little damage, some aphids are okay. Even in our urban environment, aphids have natural predators (such as lady bugs) that will keep the population under control. We actually want some aphids in order to sustain the predators so they can reproduce to eat more aphids! The key here is not to panic if a few aphids are feeding on a tree.
Getting Rid of Aphids
A heavy rainfall usually reduces aphid population. If there is no rain in the forecast, the easiest thing to do is to wash off the aphids with a strong jet of water one morning per week (morning is best, allowing the leaves to dry during the day). Doing it more than once a week helps keep the population down. You can wash leaves when you’re watering your young tree, washing your car, or watering plants.
If aphids are causing sufficient damage to warrant further treatment, or if washing with plain water has not worked, we suggest one of two insecticides. Always follow manufacturer’s application instructions:
- Neem Oil - Works quickly by suffocating the aphids. Also serves as a repellent and a fungicide. Local nurseries carry neem-based insecticides.
- Safer Insecticidal Soap - A contact insecticide that is fully biodegradable. It works by smothering rather than poisoning.
Keep in mind, using a broad spectrum insecticide will kill ladybugs, lacewings, parasitic wasps, and other beneficial insects that feed on aphids.