The Wild, Hollywood Film-Worthy Aphid
You spent the winter planning your garden & buying seeds; you spent early spring seed-starting, and summer planting out. The garden’s been growing, thriving, providing, then, suddenly….bam: aphids. Seemingly everywhere. Why?
What are Aphids?
Aphids are very small (as small as a pinhead to less than ¼” as adults) soft-bodied, sap-sucking insects in the family Aphididae. They come in a variety of colors, are roughly pear-shaped, and have long antennae. There are more than 4,000 species of aphid, approximately 250 of which are harmful to crops as well as ornamental plants. Most of these aphids have cornicles on the rear of their abdomens (cornicles are tube-like projections;—would make a great alien film creature!) Some aphids live above ground and others live below ground. The former feed on nutrient-rich plant sap; the latter attack plant roots.
Why it Seems Aphids Multiply So Quickly
The answer lies in how they reproduce: namely, that, when environmental conditions are favorable, no males are needed. Female aphids can reproduce asexually; a process called parthenogenesis. (If you thought the cornicles were cool/odd/weird, just wait…) The female’s eggs have no need of fertilization and are genetically-identical to her. That’s right: she has created clones. This means that all of those eggs which just became clones of the mother are all females just like her, who then go on to asexually reproduce more female clones. That’s right: those hordes of aphids currently eating your plants are armies of female clones. And it gets even more wild: Aphids do not lay eggs. Instead, they give birth to live young: viviparity. Only aphids, certain flies, tsetse flies, beetles and cockroaches give birth to live young, as opposed to the much more common eggs. These young newborn clones are called nymphs. Because of a phenomenon called telescoping generations, the ‘mother’ aphid not only holds eggs inside her for her ‘daughters,’ but those ‘daughters’ already have developing embryos inside them as well. When the nymphs--miniature clones of their ‘mother’-- are born, they are pregnant. They are able to give live birth to their clone daughters within days: up to 40-60 young each. So: no—it is not your imagination that a few aphids suddenly became a major population. Aphids, when conditions are favorable, are literally designed to maximize their own numbers incredibly, awe-inspiringly, quickly.
What are These Favorable Conditions?
Aphid asexual reproduction is triggered by warm weather and long daylight hours. These signal to the aphid “smooth sailing ahead!” In other words, that resources will be abundant. And, due to the high numbers of “host” plants that are growing, this indeed can become true. Aphids, like all life forms, want to live, and they want to reproduce. By switching to asexual reproduction in the warmer months of the year, they are able to dramatically increase their numbers; taking advantage of the warmth, light and abundant availability of food. In the winter, when temps and daylight hours drop, female aphids revert back to sexual reproduction. They mate with males, lay eggs instead of nymphs, and produce both male and female young. The eggs are more robust than soft-bodied nymphs and have a greater chance of surviving the winter. When spring rolls around and the light and heat increase, back to asexual reproduction they go.
What Damage do Aphids Do?
In large numbers, aphids can cause plants to produce plant galls on their leaves or roots, which are ball-like, abnormal growths created as the plant’s reaction to chemicals released by the aphid; they can cause deformation of leaves, buds and flowers, can slow and hinder plant growth, and transmit viruses. The leaves of aphid-infested plants can curl, yellow, misshape, or fail to grow. The flowers and fruit of affected plants can deform or distort. When aphids feed, the waste they produce is sticky, and sweet. This substance can encourage sooty mold, a fungal disease. Adult aphids are usually wingless, but most can develop a winged form if there is too high of an aphid population. (Of course they can!) This allows the aphids to fly to other plants, reproduce and colonize them as well. Aphids are a tremendous strain on a plant, causing it to weaken and become seriously stressed. A stressed plant is much less likely to withstand continued aphid infestation—or any other diseases, water-stress, soil imbalances or harmful insects. But what can you do against a rapidly asexually-reproducing insect with abdomen-projecting cornicles who give birth to both their daughters and granddaughters so as to shorten the time between generations?
Aphid Prevention Strategies
First and foremost, try to prevent aphids from finding your garden favorable in the first place. You cannot do much to control for daylight hours or warming temperatures, but you do have control in terms of the plants which are growing in your garden, and the conditions among those plants. No chemicals are necessary for preventing aphids, but strategic planting—along with other gardening practices—are certainly in order.
DIVERSITY: Your first preventative measure is planting a range of flowering plants and foliage. The goal is to make your garden appealing to those insects which prey upon aphids: lacewings, ladybugs and parasitic wasps. Umbelliferous plants (those from the celery family, with mostly aromatic, disc-shaped umbels with tiny flowers on short stalks) are particularly appealing to all three of these insects. Some umbellifers include fennel, dill, Astrantias, Sweet Cicely, Angelica, Cow Parsley, White Laceflower, Wild Carrot, Hairy Chervil and Bishop’s Flower. Nectar-producing plants such as yarrow, statice and nettle are also great attractors.
WATER: Providing a water source—no matter how small—can also go a long way to keeping lacewings, ladybugs and parasitic wasps in your garden.
COMPANION PLANTS: The goals of companion plants are to draw aphids to particular plants (and away from those you don’t want touched), or to repel the aphids entirely.
Repellants: Garlic and chives, planted near lettuce, roses, and peas, can help keep aphids away. A general-purpose repellant plant is catnip, as are fennel and dill (note: they also attract beneficial insects), marigolds, leeks and cilantro.
Trap Plants: Plants that draw aphids to them, helping to leave your chosen plants unscathed, are “trap plants.” These include nasturtium (an aphid favorite), which can help protect your broccoli, tomatoes and other vegetables; mustard, sunflowers, chervil, milkweed, lupine, calendula, cosmos & zinnia. It can be a bit unnerving seeing these sacrificial plants teeming with aphids, but in this case they are doing a very important job. Keeping an eye on their growth and trimming them to prevent them from touching other plants—which would allow for easy aphid movement onto your prized plants—is key.
GARDEN TIDINESS: Aphids like warm, high-humidity environments. When we let our gardens become unruly to the point of crowding and obstructing air flow, we begin creating conditions just right for aphids. Keeping a watchful eye on weeds & plant growth; taking care to space plants to allow for their full size at maturity; snipping or pruning as needed to maintain air circulation and prevent crowding or overlapping are all steps we can take to keep the aphid’s optimal conditions to a minimum.
SOIL HEALTH: Healthy soil begets healthy plants. Taking steps necessary to build and maintain balanced, fertile, alive soil helps create resilient plants. Strong plants are much better able to fend off disease and harmful pests—aphids among them—than a week or stressed plant. Avoiding all synthetics and instead amending our soil organically allows for those critical microorganisms in our soil to do their jobs.
When Aphids Colonize Your Plants
At some point, almost certainly, you will still get aphids on plants which you wish to protect. The best first step is always close observation: Walk your garden as often as possible: look not only on the tops of leaves but also on stems and especially on aphids’ favorite spot: the underside of leaves. Look closely: aphids can at times be nearly undetectable. Look, too, for already-existent damage to the plants (see What Damage do Aphids Do, above). Aphids love tender, young new growth, so take care to look closely at new shoots and leaves, as well. And also: Look for ants. When aphids suck on plant sap and excrete their sweet, sticky waste called honeydew, ants are big fans. They seek out and even take care of aphids in order to encourage the continued production of this coveted food source. If your plants are covered with a sticky substance and especially if the honeydew is present and so are ants, you may very well have a developing situation wherein you not only need to address the rapidly-burgeoning aphid population, but also the ants. Ants can go to extreme lengths to nurture their aphid food-producers, including moving their colony of aphids to a different plant if the conditions (such as you) begin to work against their favor. To prevent things from getting to this point, do your utmost to find aphids before those clones starting cloning themselves and the whole aphid/ant sci-fi colonizer scenario gets a foothold.
What to do When You Find Aphids
Even though aphids can seem as if they are unfathomably resilient, they fortunately are usually slow-moving, and, being soft-bodied, they are also easy to crush. Removing them manually and crushing them before disposal is perhaps tedious, but not difficult. If your plants are tall or otherwise difficult to reach, spraying them with a fast-moving stream of water can also detach the aphids from your plants. However, if you’re thinking to yourself “doesn’t that just move the aphids?” you are not wrong. The water blast may dislodge some of the aphids, and, if they don’t find another food source soon they will die. But aphids are tenacious (I think we’ve established that) and hosing them with water alone is not the best solution out there. I have unwittingly wiped out my entire plant by putting my hose on “jet” and blasting my poor plant to relative smithereens. And the aphids were still attached.
My favorite technique for tackling aphids is soapy water. Combine approximately 3-5 tablespoons liquid soap per gallon of water. Spray it directly onto the aphid colonies. Many will survive this initial treatment, so reapplying every 2-3 days until the aphids are eradicated will be necessary.
It’s hard—at least for me—to calmly write about crushing and suffocating aphids. It feels quite horror-story-ish. I would much rather prevent large aphid populations by taking the preventative steps necessary than have to kill them (and maybe the ants, too.) After all, aphids are a much-favored and important food source for a number of beneficial insects. And those insects are the much-favored and important food source for other creatures. And on and on.
The bottom line? Go ahead and marvel at the wild, weird, unbelievable being which is the aphid. Process the fact that there are thousands and thousands of clones already in our midst. Let yourself feel the wonder and ingenuity of nature. Plan your garden from the get-go to attract beneficial insects, trap aphids if (when) they come, and repel them as well. Put out a bit of water. Keep your garden tidy and the air moving. Be a responsible garden guardian and observe closely, and often. Remove aphids manually, and early-on. And then and only then, if you still find yourself with a burgeoning aphid situation, get out the soap and water, and be diligent. When it comes to aphids, an ounce of prevention truly is a pound of cure.