If there’s one class of insect that bothers gardeners more than any other, it has to be aphids. These tiny pests can be found worldwide and they are to plants what mosquitoes are to people – small but destructive vampires. Aphids feed on the sap of plants, which is damaging enough on its own, but to get to the sap they chew up the leaves with their efficient jaws. They also breed rapidly and won’t stop feeding until they kill the plant, at which point they migrate to the next plant and the cycle starts all over again. To a biologist aphids are actually fascinating – some species of ants farm them, for example – but to gardeners they’re a serious pest.
Luckily aphids aren’t that hard to get rid of, but you do need to act quickly at the first sign of a problem. Otherwise the speed they reproduce at will overwhelm the affected plant, and even if it survives the damage can be serious. Almost no plant is safe from them; there are more than 4,400 known aphid species, about 250 of them classed as serious pests. They vary in size from a millimeter to almost half an inch and can be a wide variety of colors. Most common are green, black and white. They generally have soft, pear-shaped bodies with a prominent tube protecting from the rear. Some of them can be mistaken for other insects but the damage they cause is quite distinctive. The leaves of an aphid-infested plant will start to turn yellow and curl inwards, and new shoots are often deformed. Another thing aphids do is secrete a sticky substance called honeydew. Ants love this, which is why they sometimes farm aphids – they “milk” the tiny insects to make them release it – but when it collects on a plant it often attracts fungus spores and causes a black infection that’s often lethal. Aphids can also carry plant diseases in their bodies, and if they suck sap from a plant that’s infected with a virus then move to a healthy one they usually infect it too. Basically they’re a nuisance and they need to go.
The first thing you can do is try to prevent them colonizing your garden in the first place. This isn’t easy. Aphids are usually wingless, but some species will have winged offspring in summer or if food runs low. That means they can get around, so no defense is foolproof. You can improve the odds, though. Any time you bring in a new plant check it carefully before you take it anywhere near your garden. Look for feeding aphids, and also check underneath the leaves for egg clusters. Aphid eggs are tiny, but they lay them in bunches so they should be visible as small white flecks. If the plant turns out to be heavily infested it’s best to get rid of it. A few aphids can be dealt with, but you need to be thorough or the result could be disaster for your whole garden. If you have any doubts at all treat the plant before introducing it.
Another way to deter the little pests is to avoid over-fertilizing. Too much fertilizer can encourage very rapid plant growth, and that means lots of fresh green shoots – aphids’ favorite food. Use slow release fertilizers; that should keep growth rates normal, and prevent your yard becoming a favorite aphid spot.
Think about other insects – aphids can have complicated relations with them. Ants are often beneficial but if you see them carrying aphids around they need to go, too. The idea of ants farming is quite impressive, but not if they’re using your plants as fields to grow aphids on. The species that do this will protect their aphids from predators and carry them from infested plants to healthy ones, to give themselves a nice crop of honeydew, so you can’t have them around. Ladybird beetles, however, are a completely different story. They look cute but they’re voracious predators, and they love snacking on aphids and scale. If you see them around your plants leave them alone – they’re very efficient at pest control. You can encourage them to settle and breed by getting a ladybug house. If you’re really in a hurry you can buy a tub of a thousand live ladybirds online for less than $10. If you have wrens in the area try setting up some small nesting boxes – these little birds also eat aphids (although they might eat the ladybirds too).
Check your plants every few days in summer, looking out for either aphids or egg clusters. If you find any, act right away. A single aphid can have up to 80 offspring in a week, and it often does only take a single one – many aphids can lay eggs without mating. If you find any, the first thing to try is just washing them off. A high-pressure hose attachment like a Bug Blaster will knock them off, and usually they won’t be able to get back onto the plant – they aren’t very mobile once they’re on the ground. Alternatively mix two teaspoons of dish soap into a pit of lukewarm water and spray the infected plants with it. Soap suffocates aphids by clogging the pores they breathe through. If you don’t fancy using dish soap you can also buy special insecticidal soap. It can take several applications to cure the problem, and it’s best to spray neighboring plants as well. Make sure to soak the undersides of the leaves – miss those areas and newly hatched aphids will be munching away within days.
In extreme cases insecticide powder or spray might be needed, but these can be hazardous to children and pets, and you don’t want to use them on vegetable crops if you can avoid it. Soap works as well as nearly anything. If one of your plants has a really bad case you can prune away the worst affected parts – sometimes you might need to sacrifice the whole plant, if it’s already sickly and has a very heavy infestation.
Aphids are some of the most destructive insects you can find, but regular checks and some simple treatments will keep them under control. The trick is to not leave them undisturbed – if you do that your garden will quickly be overrun and badly harmed. Be vigilant for the tiny pests, and take action right away if you find them. Infestations are very common but you don’t need to let it ruin all your hard work.