How do I manage a large outbreak of aphids?

June 14, 2023 Ask the Expert, Managing Insect, Diseases, and Animal Pests

Question:

I have a huge burning bush. The last few years I have been battling aphids. Last year I didn’t do anything and realized the problem wasn’t that bad after not spraying it with soapy water as usual. This year, however, they are incredibly bad. They seem to have taken over the entire bush, including the not so new growth. Additionally, I have them in a nearby holly (they haven’t been there before), and in perennials I have planted beneath the bush. This morning I have found some in my nearby flower bed. I am loath to use pesticide, but now will, but I’m not sure how to treat a shrub so large and what with. Looking for advice. I don’t want to kill pollinators and a lot of my flowers attract hummingbirds.

Answer:

Jonathan Foster, Special Project Assistant

I’m sorry to hear about your aphid woes–I recently dealt with an outbreak on my indoor purple passion plant.

As you note in your question, 1) aphids are often not a huge problem as long as their population is kept in check, and 2) once they reach a critical mass, they can be quite a nuisance. The most organic method of control, and often a quite effective one, is the spray of water. Soapy water can help kill the aphids, as it sounds like you know, but a particularly strong jet of water will dislodge/kill most of them physically, as well. So I suggest trying that if you haven’t yet.

If that hasn’t worked, though, I recommend reviewing our UMaine Cooperative Extension Pest Mgmt Fact Sheet #5039 for suggestions on chemical control. As you will read, the treatments (in rough descending order of “organicness”) are insecticidal soap, horticultural oil, neem oil, and malathion. I will note that insecticidal soap worked well for me with my purple passion, but it does require direct contact with the aphid to kill them and it washes off easily and must be reapplied.

As always with chemical interventions, please read the instructions carefully and follow them diligently to achieve maximum effectiveness and to protect yourself and the environment.