How to Handle Aphids

Continuing our ongoing discussion of common pests and how to best control them, we’ll be going over aphids in this blog. In many areas of the United States, they are one of the most common pests a gardener will encounter.

While some unwanted visitors, like deer and rabbits, are easy to notice, the aphid’s small size makes them harder to spot when they first show up. You might notice the damage they’ve caused before you notice them marching around on the garden you’ve worked to keep spotless.

Thankfully, these annoying little bugs can be controlled. By knowing their signs, you can swiftly intervene before they make a buffet of your favorite plants. You’ll really want to stop them sooner rather than later, too. They reproduce quickly, and dealing with many of them is a more involved task than dealing with just a few.

What are they?

Aphids are small bugs that typically don’t exceed ¼ inch in length. There are many species, so color can vary from green to brown to white, and so on. Most do not have wings, but some will!

Because you can’t typically identify them by wings or color, we recommend looking for the features that most species do share: a rounded, pear-shaped body with two antennae (or “tail pipes”) poking out of their rear.

Often they’ll be in large groups, which helps when trying to spot them. It’s rather rare for aphids to hang out alone, but it does happen on occasion. 

Ants will sometimes congregate near aphids as a source of food, so checking for aphids near groups of ants in your garden isn’t a bad idea. They commonly hang out on the underside of leaves, so we recommend starting your search there.

What do they do to plants?

Just like their looks, aphid damage can differ slightly from species to species. Some aren’t picky eaters and will munch on just about anything. Others have strict diets of specific types of plants and will only feed on the few varieties they’re accustomed to. Regardless of the plant there are a few calling-cards to look out for if you suspect that a group of aphids is eating on your dime. Look out for:

• Leaves that are yellowing or curling up when they shouldn’t be
• New growth that has become stunted
• Deformed flowers (or veggies and fruits)
  • Aphids can transmit viruses to plants, which causes this damage
• Galls, which are (usually) bulbus formations on leaves and stems that some species of aphids reproduce and lay eggs in
  • Not all aphids will create galls. Similarly, aphids are not the only insects that can create them
  • Galls can vary widely in appearance based on what created it, the type of plant, and what part of the plant it’s on
• honeydew, which is a sticky, sugary substance that aphids leave behind after eating
  • Because it’s sugary, it can often attract other pests
  • Honeydew can also lead to sooty mold, a black fungus that can appear on leaves, branches, and stems

Eek! That doesn’t sound good, how can I prevent them?

There are a few different methods that gardeners use to keep aphids at bay. No method is perfect, and the “best” one will depend on your unique situation. Thankfully, small populations of aphids are usually a non-issue, and are generally easy to keep in check. To keep their numbers as low as possible, try:

• Planting things that aphids don’t like. Some plants they tend to shy away from include:
  • Onions
  • Most aromatic herbs, including garlic and chives
  • Catnip
  • Marigolds
• Plant “trap plants”, which are things that aphids love and will tend to congregate on. This makes it easier to find and remove them, while keeping from feeding on something you’re more concerned about. Common ones are:
  • Nasturiums
  • Mustard
  • Sunflowers
• Introduce natural predators of the aphid, like ladybugs, into the landscape
• Use a bit less fertilizer, as aphids love plants that are high in nitrogen

What if I already have aphids damaging my garden?

If aphid populations are already large enough in your garden for signs of trouble to appear, start with the least extreme measures and slowly ramp them up over time until you begin to see results. Like with prevention, not all of these methods will be a fit for every garden. Research them and decide if they’re right for you. They are:

• Spraying plants with a hose
• Once knocked off their “home” plant, they usually have a tough time finding their way back
• Apply a mix of water and a tiny amount of dish soap to the leaves of plants
  • This will keep away, but it should be reapplied every few days or after rain
  • Be careful to not use too much soap, as it can potentially harm the plant
• Apply neem oil to areas where aphids have been spotted
  • This should only be done on well-established and otherwise healthy plants, as it can damage new and weak ones
  • Neem oil can be harmful to foliage, so keep it mind that it may discolor some areas
• Sprinkle food grade diatomaceous earth in your garden
  • It’s entirely natural and nontoxic and can even be used on edible plants
  • Though it’s nontoxic, its makeup of mostly silica means that it shouldn’t be breathed in
  • Its biggest downside is that it can also potentially kill beneficial insects, so only use it on areas where that isn’t a concern, or during portions of the season where pollinators and good insects aren’t as common
• Chemical treatment options
  • As a last resort, certain insecticides can be extremely effective. However, they can also come with some nasty side effects if you’re not careful. If you wish to go this route, we encourage you to visit your local garden center and ask about what they recommend for your area

Did we miss anything?

If you have other tips for aphid control that we didn’t mention here, let us know on social media! The same goes for further topics you’d like to see more on; we’re happy to provide the content that our gardeners are looking for most. We hope this brief overview helps to keep your garden aphid-free and growing strong! As always,

Happy planting!