# Oleander aphid

*Aphis nerii*

The bright yellow aphids that coat a milkweed stem, all of them female, all of them clones, and none of them native.

## What it does on milkweed

Aphis nerii feeds on the sap of milkweeds, oleander and their relatives. In North America the species is entirely parthenogenetic: no males are known here, and every aphid you see is a female producing live female clones, which is why a colony appears overnight. Like the plant’s other specialists it stores cardenolides, and its yellow is a warning. It draws in ladybirds, lacewings, hoverfly larvae and the parasitoid wasp Lysiphlebus testaceipes, which leaves behind papery brown mummies.

## How to recognize it

Small, bright lemon to orange-yellow, with black legs, black antennae and two black cornicles projecting from the rear. Densely packed on stems, buds and the undersides of new leaves.

## Where and when

Everywhere milkweed is grown in the United States.

## Should you do anything about it?

Do not spray. Every insecticide that kills aphids also kills monarch eggs and young caterpillars. Rub the colony off with your fingers, blast it with water, or leave it for the predators, which usually arrive within a fortnight.

### Do oleander aphids kill milkweed?

Rarely. Heavy colonies distort new growth, reduce flowering and leave sticky honeydew that grows sooty mold. Established plants tolerate them. Seedlings and container plants suffer more.

### How do I get rid of aphids on milkweed without hurting monarchs?

Squash them between finger and thumb, or knock them off with a jet of water, checking the plant for eggs and caterpillars first. Do not use insecticidal soap, neem or any systemic treatment.

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Source: https://milkweedusa.com/wildlife/oleander-aphid/ — Milkweed USA, CC BY 4.0.