At one time I thought aphids were boring. Oh sure, they come in pretty colors like gold and green and some in a more drab display of black and gray. But mostly when I saw aphids, I thought of the same repetitive scenario: curled up leaves, deformed flowers and buds, sooty black mold, ants, ants, and more ants.
Contrary to what I used to think, aphids don’t arrive on my plants to torment me. Instead, they are there to do a job that consists of sticking their pointed mouth part into succulent plant growth and sipping out the nice sugary syrup within. They always take more in than they can assimilate and excrete the excess. This excess is known as honeydew. A black sooty mold grows on the honeydew, which makes plants look dirty. It also reduces photosynthesis which in turn weakens the plant.
These small (less than 1/4" long) teardrop-shaped insects seen in clusters on healthy plant growth are one of our most common garden pests. Their remarkable life cycle of bearing live young explain why they appear in such large numbers so quickly. Females lay their eggs toward the end of the growing season in protected places such as cracks and crevices of bark and bud scales. When spring arrives, plump aphids emerge from these eggs. These are know as “stem mothers,” and they give birth to daughters, and they to more daughters, all without mating. More extraordinary still is each new female born already has her partially formed daughters within her. At the end of the growing season, males are finally produced. Females are then born with eggs rather then live young. Mating then occurs and the eggs are again laid once again in protected areas on plants.
Aphids have many natural enemies. Often these adversaries are present in the middle of the growing season, so at the beginning and end of the season, aphids can feast on our plants without danger of attack. This causes the populations to explode. This surge of aphids happens for two reasons. One, is the nitrogen level in plants is higher at those times, which attracts pests. Using slow release organic fertilizers, such as cottonseed meal, fish emulsion, kelp meal, or chicken manure will keep nitrogen levels adequate but not excessive and will help keep populations down. Second, there are fewer predators at those times. Since the control of aphids improves as the season progresses and beneficial/predator insects arrive, you will want to create a habitat for these good guys. This is accomplished by discontinuing the use of toxic pesticides and planting flowers that attract and provide nectar for the beneficials. Some popular varieties are: scabiosa, yarrow, sweet alyssum, asters, sunflowers, daisies and herb blossoms such as oregano, cilantro and borage. More about Beneficials.
Ants are fond of the honeydew excreted from aphids, and in turn, kill off beneficial insects that take away this food source. Look for creative non-toxic controls to keep ants away from your aphid colonies. Further strategies consist of hosing off the offending aphids, wiping them away with a damp rag, pinging them off with your finger, pruning severely infested sections, and as a last resort using insecticidal soap or a light horticultural oil available at most nurseries.
In the past ten years I have nurtured a natural enemy habitat in my garden consisting of at least five nectar flowers for beneficials, a shallow water source for them to sip from, and a little batch of sugar water to keep the ants distracted. As a result my garden rarely has a problem with aphids. When they do arrive, I monitor how many there are, and only if it’s needed, do I hose them off or spray a little soap to kill them. Most of the time I leave them for their predators. Now, instead of swearing at them, I pull out my 10x hand lens and look for tiny parasitic wasps and other predators, or if I’m really lucky I can watch a baby aphid being born alive. What better way to spend a sunny spring afternoon?