Root aphids – a cousin of standard green or stem-and-leaf aphids – belong to the family Phylloxera, and typically exist at or below the soil line. They are a prominent issue for indoor gardeners, but may also affect outdoor crops. Unlike other aphids, root aphids are much more likely to overwhelm your plants and kill your crops. This is because they attack the central source of the plant’s nutrition – the root system.
Dealing with a Root Aphid Problem
Root aphids are minuscule and colored to blend in with the soil. The primary way to identify a root aphid infestation is via the waxy substance that they leave behind. If you begin to notice a chalky, white residue (also known as “honeydew”) on any part of your plants, you should begin to suspect that something undesirable is feeding upon them.
Similar to mealybugs, root aphids’ bodies are somewhat teardrop-shaped. As a matter of fact, root aphids are often confused with mealybugs due to their shape and the honeydew substance they leave behind. Some root aphids progress into a winged stage in order to travel to other plants, at which point they are also commonly mistaken for fungus gnats. One simple way to distinguish all breeds of aphids from these other insects is to look for the conical tail protruding from the end part of their torso.
Root aphids are most destructive because they are quite adaptable to both indoor as well as outdoor conditions. When found outdoors, they are often accompanied by ants, which only further compounds the problem and makes their eradication that much more difficult. The ants will often carry the root aphids’ eggs to other locations, spreading the problem. Root aphids’ eggs are capable of surviving through the winter beneath the soil, or they will attach to low-hanging stems and leaves in the warm season, allowing the root aphids to fall to the soil once hatched.
Many commercial-grade soils also contain root aphid eggs. Probably the best advice for avoiding root aphids is to always avoid purchasing bagged soils unless they are from a local, reputable source. Additionally, avoid purchasing soil from large nurseries, or otherwise importing soil or compost from unknown locations. Always make your own soil and compost whenever possible.
Getting Rid of Root Aphids
The most effective method for treating a plant that is noticeably affected by root aphids is to remove and destroy the entire plant. Waiting to see if the plant will still flower, produce fruit or otherwise thrive is not recommended as the longer the aphids are allowed to remain, the more widely the problem is likely to spread. When removing the plant, take care to keep the root aphids and eggs as contained as possible – avoid shaking the plant and dropping any aphids or eggs onto the soil or any healthy plants below.
If you are not keen on removing your entire plant, it is possible to cook the soil in order to kill the aphids. If you have an indoor garden, remove the plant from the soil, then remove the soil from the container. Place soil on a baking sheet and bring up to temperature. If outdoors, the same effect can be achieved by placing a black tarp over the affected garden soil on a sunny day. The effectiveness of this solution varies, so be sure to check for remaining root aphids after treatment.
Yellow sticky traps are recommended to assist in trapping any moving root aphids. Beneficial nematodes can also be added to your soil in order to help with the eradication of these insects.
Insecticidal soaps are not recommended as a treatment for root aphids. This is due to that fact that they will not kill any bugs located beneath the soil. Instead, we recommend you treat your plants with neem oil or a pyrethrum-based spray, which will need to be used early during the infestation. You may also water a Spinosad-based insecticide into the soil, or utilize Beauveria, a fungus that contains spores that will attack the root aphids.
Beneficial Predator Insects
Finally, we recommend attracting predator species such as birds which will pick the aphids off of your outdoor crops. You can also introduce parasitic wasps and ladybugs, which will both eat any root aphids found above the soil.
Root aphids can certainly do quite a bit of damage to indoor and outdoor grow spaces if not caught early. Make sure to stay vigilant, as these creepy crawlers are one of the big reasons we check our plants daily! If you notice signs that the root aphids have moved in, evict them quickly and save your plants following our instructions above. But remember, if you must destroy one plant, it is much better than losing half of your garden due to an infestation that has been left to spread.