Aphids be GONE! What can we do about those nasty little yellow aphids we see on milkweed?
What can we do? First, let’s go over a few facts about this species of aphid, Aphis nerii.
- They are called both milkweed aphid and oleander aphids.
- They do not lay eggs. Females give live birth.
- There are no males in the wild in the US.
- Winged aphids travel to new plants by flying.
- They kill some milkweed plants, especially smaller plants.
- Although most are on new growth, they are also found under old leaves.
- Primary damage is visual. This is caused by sap being drawn out of the growing point of the plant.
- Aphid excrement falls on leaves below them. On this sticky excrement grows sooty mold, a black coating that will cover the leaf. This prevents sunlight from reaching the leaf, causing it to eventually die and fall from the plant.
- Aphids attract beneficial insects (that eat aphids). This is wonderful. (They may eat a few eggs and young caterpillars but the good they do overwhelmingly overcomes any eggs/caterpillars they eat.)
What can we do? (Remember to click on links, indicated by underlined purple words.)
We encourage everyone to avoid harsh pesticides. Below is a step by step guide to controlling aphids. Please remember not to touch your face or eyes while touching milkweed. If possible, conduct a daily aphid check on your plants until they are totally under control. At that point, check every other day for a couple of weeks. After they are under control for two weeks, check weekly for aphids.
Once you reach step 3, always remove eggs and caterpillars first. The part of the leaf where an egg is attached can be cut off of the plant. After treatment and the plant is safe again, that piece of leaf may be stapled to a leaf. It is not necessary for eggs to be on living plants. As long as the hatchling caterpillars can crawl off the dead piece of leaf to a living leaf, they’ll be fine.
- Milkweed new growth (tip of each branch) that are heavily laden with aphids can be cut from the plant and disposed off-site in a sealed container. Freezing the container for a couple of days in the freezer is not a bad idea.
- Hand squash aphids by simply squishing all the aphids we see on the plants. This involves checking under all leaves. Gloves are a nice accessory for this task. Many of us never wear gloves while squishing aphids and have the yellow fingers and thumbs to prove it.
- Remove them with a strong blast of water. First, all eggs and caterpillars should be removed and placed in a secure container. After aphids have been removed, caterpillars and eggs can be returned to the plant. One disadvantage is that any aphids on the ground can crawl back to the plant.
- Remove all eggs and caterpillars and place them in a secure container. Using a cotton swab, dab aphids with rubbing alcohol. Alcohol is deadly to caterpillars and eggs. After killing aphids, rinse the plant well. Return eggs and caterpillars to the plant.
- Add beneficial insects to your garden. Many of the critters you see on milkweed may actually be killing your aphids. Learn what they look like. Check with a reliable supplier before purchasing beneficial insects. Some beneficial insects will immediately leave your garden rather than staying to kill aphids.
- Remove all caterpillars and eggs, placing them in a secure container. Early in the morning or late in the evening, spray the plant with soapy water. Cover the plants with a sheet to keep insects from landing in the soapy residue. Thirty minutes later, rinse the soap off the leaves, top and bottom. Soap is a deadly diet for caterpillars. Once the plants have dried, return eggs and caterpillars to the plants. (Sunlight is magnified when it shines through soapy water. In the middle of the day, it can kill the leaves on your plants. Treat plants with soapy water only in early morning, late evening, or on an extremely cloudy day.)
- Insecticides should be avoided if at all possible. If it becomes necessary to use a non-systemic insecticide, first remove all eggs and caterpillars. After we have completely followed the directions on the package, we should cover our milkweed plants with a light colored sheet for several days. Most insecticides will kill beneficial insects as well as aphids for days and often, kill beneficial insects for weeks or months.
- As winter arrives and plants are frozen to the ground, we suggest raking all leaf debris two feet out from around the base of the plant. Some aphids may be protected from harsh winter cold by spending the winter in old leaves and mulch. Dispose of these off-property.
Side note: Other species of aphids will also become plant pests on milkweed and other plants in your garden. This manner of control will help reduce or eliminate any species of aphid.