Aphids are tiny but nasty insects that live on the growing tips of plants, typically the new spring growth of shrubs and trees. Their food is the plants’ fluids. Unless a plant is already very unhealthy, they don’t kill it, but they do look awful. Here is a picture, taken today, of aphids on one of my shrubs, a cranberrybush viburnum (V. trifolium):
Ick. Notice that the stem tip is solidly covered with shiny black aphids, and that ants are all around–they get their food by “milking” the aphids. But notice as well that the leaves look healthy, except for the pair of leaves at the very top of the stem.
Now let’s step back and look at this entire plant:
Notice that this shrub and the surrounding shrubs look perfectly healthy–deep green and in bloom. On close inspection, I saw that the aphid damage is confined to the tips of three branches.
So what should I do? I will consider the following information: each species of aphids attacks only one type of shrub, so the dogwoods, elderberry, and ninebark shrubs in the same hedgerow as this viburnum are not in danger. Aphids attack only the tender growing shoots of woody plants, so once this spring’s new growth begins to harden, or lignify, the aphids can’t do any more damage. And because aphids are so common, they have many natural predators, especially ladybugs, whose larvae devour aphids in tremendous numbers.
So here’s what I’m going to do about this aphid infestation, and what I recommend that you do if you see aphids in spring on a woody plant:
1. Keep an eye on the affected plant and on the other plants around it to make sure the aphids don’t get out of hand.
2. Watch for ladybugs to arrive on the plant.
3. Watch for ladybug larvae to develop after ladybugs lay their eggs on the plant (the eggs are too small to see, but the larvae look like tiny black-and-red alligators). The larvae will take care of the aphid problem.
Horticulturists call this approach “integrated pest management.” I call it “wait and see.” Watch carefully, and wait patiently for nature to take care of the problem for you.