Root Aphids 101


The foliage turns yellow and practically no new growth is produced. Root aphids attack many garden plants, including aster, Braille, calendula, primrose, and sweet pea, as well as corn and strawberries.

Spot them


Healthy Roots

Root aphids generally have short legs and short antennae, and, thus, are especially adapted for life in the soil. Where large numbers of these insects are present, they suck out so much sap from the roots that the plants do not receive sufficient nourishment. These little aphids are often attended by ants. The ants not only look after the over-wintering aphid eggs, but, in the spring and summer, sometimes actually carry the lice through the soil from one host plant to another. In fact, if a plant, especially an annual, looks sickly and ants are found on the ground nearby, it might be well to hunt for root aphids.

Aphids feed from the phloem of plants which they tap into with the stylets (piercing parts) of their proboscis. They gain access to the phloem vessels from 3 main parts of the plant, stems, leaves, and roots. Their stylets, which are contained within the proboscis when the aphid is not feeding, are very thin and could suffer damage while being pushed into the plant or bend in an unwanted direction. Therefore aphids secrete a special liquid from the tips of their stylets which starts to harden as soon as it leaves, forming a hard protective sheath around these piercing mechanisms.  They are slowly pushed into the plant in search of the phloem tubes. When they reach a phloem tube the aphid injects saliva into the plant cell. It is suspected, but not known for sure, that this saliva helps prevent the plant cell from sealing the puncture with special proteins. These special proteins are the plants normal defense mechanism. Aphids insert their stylets slowly and it takes quite a bit of time to tap into a phloem tube; it can be anywhere from 25 minutes to 24 hours from starting to insert the stylets to actually getting something to eat.

Some of the many species of aphids attack the roots of plants and these can stunt the growth or even kill them, if the infestation is large enough. They are usually associated with particular plants or groups of plants. Root aphids have a similar life-cycle as ‘normal’ aphids. Root Aphid starts the seasonal cycle on leaves when the females hatch from overwintering eggs, then cause a gall to form in which she gives birth to many winged, female young which move to the roots to continue the cycle with several more generations in a season. These summer forms produce a white, waxy material characteristic of most root aphids, and this can often be mistaken for beneficial mycorrhizal fungi, which reproduce asexually. In the autumn, a generation of winged aphids are produced which fly back to the trees and these give birth to wingless males and females which mate to produce the over wintering eggs to complete the cycle.


Liquid pyrethrum concentrate was mixed into the water/nutrient mix. Pyrethrum is an organic pesticide refined from flowers in the chrysanthemum family.  However, it isn’t considered to be “organic” as the refining process isn’t completely organic.  Bug buster –O by Fox Farm (not available in CA) is a mild concentration so it is recommended for preventative to light infestations.   Most folks recommend using 2 oz per gallon of water for drench or hand water over your pots or rockwool.   It is recommended to  top feed with it, even if you drip or flood and drain, or re-circulate any hydroponic system, you will be guaranteed better coverage.  Then flood table for about 1 hour.  (Use the 2 oz. per gallon and fill up reservoir).  Do once every 4 days until they are gone.  It should take only two treatments.   For larger reservoirs or gardens a stronger Pyrethrum is recommended. Remember, Pyrethrins, will kill any beneficial that you may have added to your medium or soil, so don’t forget to re-inoculate.  The only down side is with the increasing regulation on pyrethrum products, and the difficulty of procuring said products, gardeners have had to figure out other ways to stop this pest.

Beauvaria bassiana is a beneficial fungus that infects soft-bodied insects. When a possible host insect brushes against the fungus spore, the spore attaches itself to the insect. Then it grows hyphae, which are simple thread-like filaments, into the body of the insect and starts feeding on the insect. When the insect dies it releases more fungus spores that are ready to germinate when they come in contact with a suitable host such as another root aphid.   The products that contain this organism are difficult to procure in some states because of Ag laws.  When using one of these products, make sure to USE NON- CHLORINATED WATER

azasolWe have been having a lot of success with high concentrations of Azadactrin.  Aza-Sol has been working well, as has Vital Earth’s Neem concentrate.  They seem to be a little stronger than Azamax and Azatrol.  The latter working wonderfully in the preventative program, where as the former are a little better on the curative tip.  Over the past year folks have also been raving about Sierra Natural Science’s, SNS-203, a natural, organic, effective root drench that does great work stopping these pesky buggers among other pernicious root feeding soil dwellers.

pred-todesOne of the best preventative practices is the introduction of beneficial, predatory nematodes into one’s garden.  These nematodes are microscopic carnivores that attack all kinds of insects in all stages of growth. Once the nematodes come in contact with the insect, whether adult or pupae, it is walking dead. After the feast, the nematodes do just what you’d expect, so thousands more hungry nematodes enter the scene looking for a good meal.   Follow directions on packages.   This is another program that definitely works best as a preventative.  While they can regain control after a serious infestation, they don’t quite cut it. They are an effective, lesser cost, biological alternative.  USE NON- CHLORINATED WATER


One Response to “Root Aphids 101”

  1. Thanks for the tips! Aphids are a pain…