The squirming, sucking infestations of aphids are not exactly lovable, but they do have real value and they are not that hard to manage. Aphids are the bottom of the food chain, like plankton in the ocean: everything eats them and they are plentiful nutrition. I have even watched small birds like wrens and chickadees lean under leaves and eat the aphids. Aphids are a food source for many beneficial insects including lady bugs, lacewings, syrphid flies and parasitic wasps, and if we kill off all the aphids, the beneficial insects will not have enough food to prosper and will not lay their eggs in your garden.
We need to learn to respect Nature more and we need to learn to get over the ick bug thing and look closely. Learn how to recognize our allies: the ladybug larvae look like little orange and black alligators! And lacewing eggs are those pale green oval eggs on long stems on the undersides of leaves, and the larvae that hatch look like tiny crocodiles. A syrphid fly larva looks like a tiny worm with pointed end. These creepy critters are the aphid clean-up crew if you leave them to do their work. We need to have patience and refrain from spraying, because there is a natural order: first comes the food (aphids), then a little later come the hungry beneficial insects.
It is well known that most plants can tolerate low to moderate numbers of aphids without noticeable damage. And, get this: the plants respond to insects feeding on them by increasing their production of defense chemicals, which they share and communicate with neighboring plants. Even the sound of feeding will stimulate the plants’ production of phytochemicals. So, allowing some insect damage on your plants actually makes the garden stronger and more resilient to other insects. Aphids, for example, are host-specific, so the aphids feeding on your roses will not feed on your lettuce, and vise-versa.
But large numbers can distort the foliage and cause some harm, so humans can help limit the numbers and still feed the beneficials. The first line of defense is a strong stream of water. A brass nozzle on the end of your hose produces a stream of water that makes a small hurricane-force blast to dislodge aphids, which cannot easily get back where they were. On the ground they are easy prey for beetles and spiders. Spray roses shortly before their buds open so the strong stream of water will not harm the flowers. One or two sprayings will often solve the problem; we want to leave at least 20% of the aphids for food for the beneficials.
For a more difficult pest or aphid problem, a non-toxic spray of horticultural oil or insecticidal soap will kill soft-bodies insects like aphids. Neem is effective too, but Neem is tricky: you must dilute it with warm water and a little liquid soap or you run the risk of burning the leaves. Once again, intend to leave 20%. Total annihilation is neither realistic nor ecologically sound. Often if you hold your breath, and wait a week, and Look, you will see the beneficial predators reducing the aphid population. And they are likely to be helping to control other insect pests as well. So if not more than 20% of the foliage is damaged, do nothing; let Nature take her course. It can be the most satisfying strategy.