Root aphids are a big problem for succulent plants and root crops.
These pests invade the roots of plants and deplete their root systems by sucking the juice from the roots.
This stunts plants’ growth and causes their leaves to wilt and turn yellow.
Some of the favorite plant “roots” these aphids’ love include:
- Hosta
- Coreopsis
- Asters
- Veronica plants
- Sedum many varieties
They can cause significant damage to hickory, walnut and fir trees and have been known to devastate rice crops.
They can also do a great deal of damage to herbs such as basil and oregano and are incredibly problematic to marijuana growers.
What Do Root Aphids Look Like?
There are three types of root and crown aphids. They are:
- Hawthorne/Parsley aphids (Dysaphis foeniculus and D. apiifolia) is grayish white in color.
- Tulip bulbs aphids (D. tulipae) looks something like a mealy bug because it is coated with white waxy powder.
- Hawthorne carrot aphid (D. crataegi) may be yellowish or greenish gray and has a light waxy dusting.
Because the root aphid is white, many gardeners mistake them for mealybugs.
You can tell these two types of pests apart because mealybugs are quite a bit larger than aphids found on roots.
Additionally, root aphids’ bodies are teardrop-shaped, and they have two pointy protrusions (cornicals) on their hind ends.
Aphids feeding on the root system are closely related to leaf and stem-sucking aphids. All belong to the Phylloxera family of insects.
Unlike their aboveground cousins (e.g., green peach aphids and melon aphids) root aphids are relatively stationary.
How Do You Know If You Have A Root Aphid Problem?
Aphids attacking root areas below the soil line congregate in groups underground on the roots of plants, causing root aphid damage.
You can recognize their presence by the masses of soft, white tissues on infested plants these colonies build in the roots.
They’re sometimes referred to as white soil mites.
However, if you find big infestations on your plant roots, it will be too late to do anything about it.
Root aphids move from one to place to another on their own in a very slow manner. You may occasionally see them spread about on the lower parts of the plant.
They may crawl up plant stems and attack the body of the plant. But for the most part, they congregate in the roots.
You may see aphids at the base of plant stems and the tops of the roots. They congregate in colonies and occasionally form just below the surface of the garden’s soil.
Even if you don’t see the aphids, you may be tipped off to their presence because ants tend to be attracted to the honeydew these pests excrete.
Additionally, ants may manage aphids on leaves and roots by carrying them from ‘old,’ spent plants to fresh ones.
Related: Aphid Control on Succulents
What Kind of Damage Do Root Aphids Cause?
Root aphid eggs overwinter in the garden, and immature aphids emerge in the spring to go to work using their piercing-sucking mouthparts on the tender roots of young plants.
Affected plants wither, turn yellow, and die.
Gardeners often misidentify this condition as nutrient deficiencies and lack of the mineral magnesium, but it may be your first indication of an aphid infestation.
If their devastation goes unchecked, these pests will multiply rapidly and destroy the plants they infest.
Once they consume all food sources, the insects slim down, grow wings and fly off to mate, lay eggs and start the whole process over.
In the autumn, you may see quite a few winged root aphids flying around.
At this life stage, they tend to resemble fungus gnats.
However, you can identify them by the tell-tale cornicles, which still protrude from their hind ends.
NOTE: Cannabis growers are finding tremendous damage from rice root aphids feeding on the plant’s root system.
How To Get Rid Of Root Aphids
The best thing to help eliminate root aphids is to keep your garden equipment clean, rotate your crops, and be vigilant to catch the presence of these pests quickly.
Yellow sticky traps will not work.
Practice good garden hygiene. Irrigation water running from one plant to another can carry root aphids from plant to plant.
They may also travel on gardening tools or inside reused containers.
Always sterilize garden tools, pots and any other item which may come in contact with aphids in soil root balls or on the roots of your plants.
Avoid root aphid infestation by checking the roots of your plants occasionally. This is easier with container plants than garden plants.
When you see aphids in plant roots, you are far better off just getting rid of the plant than attempting to treat it.
When you remove affected plants, dig up a large amount of surrounding soil.
Contain the soil in a bucket or plastic bag to avoid spreading the aphids as you carry the plant and soil to the garbage bin.
Introducing beneficial nematodes to the soil can help keep root nematodes under control. Some parasitic wasps and birds do eat root aphid eggs.
Generally, it is difficult to control these pests through natural means. For details read: How To Get Rid Of Root Aphids Naturally
Throughout the root aphid life cycle, these aphids are underground and protected from most natural parasites and root aphid predators.
Furthermore, the ants who attend them will fight off these natural garden helpers.
Are Pesticides Effective For Aphid Pest Control?
It is challenging to manage and kill root aphids through the use of insecticides. Use a soil drench and thoroughly soak the growing medium.
The type of growing medium used makes a big difference in how effective the method of drenching is to control root zone pests.
If the soil drains rapidly and contains a great deal of peat moss or bark, it will not work as well as a more dense soil.
Additionally, the wax coating on these insects provides them with a great deal of protection against contact insecticides.
Systemic insecticides may eventually be useful, but these bugs reproduce rapidly and are very likely to get out ahead of you even with a systemic insecticide.
If you do want to try a pesticide to control root aphids, the Michigan State University Extension recommends the use of dinotefuran or imidacloprid.
Other possible choices include cyfluthrin, malathion, and thiamethoxam.
Even though these are the most effective insecticides against root aphids, it’s important to understand that, used as a soil drench, the pesticide will move up into the plant and may not remain in the roots long enough to affect the pests very much.
Use Pesticides With Care
If you choose to use one of these pesticides, be sure to follow up with a second application approximately two weeks after the first.
Understand that using these pesticides can do quite a bit of harm to beneficial pollinators.
Both dinotefuran and imidacloprid are neonicotinoids and are quite toxic to bees, butterflies, and other valuable beneficial insects.
As a natural alternative, try using a neem oil drench solution. However, this solution has the same drawbacks as any other drench solution.
Furthermore, if you decide to use a neem oil drench, you’ll need to reapply it every couple of weeks throughout the plants’ growing season.
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