What to do When Root Aphids Have Taken Over Your Plants

By Lee McCall
Published: August 7, 2018 | Last updated: May 4, 2021 11:12:43
Key Takeaways

Heat can bring out the worst problems in indoor gardens. Root aphids are a particular setback that can do massive damage to your roots. Here are a few tips on how to keep your plants safe and sound from these nasty bugs.

Source: Floki/Shutterstock

Whatever the reason, excessively hot temperatures are not favorable to an indoor gardener. Hot temperatures break down plant immune systems, leaving gardens susceptible to attack and infection. If not properly equipped, a system designed for perpetual harvest can begin to collapse as a result of stress input on the plant. Debilitating stress can be caused by a number of factors, including insects, molds, blights, mildews and viruses.


Damage From Root Aphids

Root aphids, the spider mites of the new millennium, are a particular problem. They will infest all grow mediums from rockwool and hydroton to coco and soil, and they crawl to and from containers, pots, cubes and trays, as well as fly about. These little suckers have taken over many gardens; in fact, younger adolescents will devour root systems in hours, turning healthy vibrant plants into wilted standing sticks overnight.

The damage ultimately results in root disease, which many gardeners often mistaken for the primary cause of failure rather than the root aphid itself. As such, inspect for root aphids if you are experiencing root disease despite having ideal water or root zone temperatures. If you look close, they can be seen darting through the atmosphere of rooms (sometimes they are mistaken for fungus gnats, but they are visually more aggressive in flight) and swarming in and around the root systems.


Their bodies are round—as opposed to slender like thrips—and are much larger than spider mites, and the coloration of adolescent species ranges between hues of red, brown, green and black.

Close up of a colony of root aphids (Trama troglodytes) sucking on dandelion roots.Source: Tomasz Klejdysz/Shutterstock

Damage caused by root aphids is notable in a variety of ways. Sudden wilting or death of what were thought to be healthy plants is a common sign of a root aphid attack. Plants will suddenly collapse as a result from over stress to the plant system. Mucus membranes coating aeroponics roots and the smell of must or dirt is a sign that negative pathogens are dominating the plants’ immune systems.


Growth will slow dramatically along with water consumption, and leaf production might grow at half the rate and size of normal. Discoloration in leaf tissue is a sign of nutrient deficiency or lockout, which ultimately results from a damaged root system’s inability to absorb proper nutritional elements.

Read also: Want Big Cannabis Buds? Start at the Roots


How To Prevent And Fight Root Aphids

Preventative measures are applicable and available in various forms to combat outbreaks of aphids. Many growers will treat with supplemental micronutrients or vitamins in attempt to solve nutritional deficiencies; however, in actuality, a pesticide is needed. Poisonous pesticides and insecticides are available for immediate systemic control, but I recommend treating with natural and organic alternatives if possible. Poisons are much more hazardous to handle in comparison and will require stricter measures of safety standards when applying them to gardens.

An effective biological control is live ladybugs, which are available at most gardening centers. Ladybugs are most effective on smaller plants, as they are easier to “clean.” The bugs easily scan over cuttings for aphids within a matter of minutes. They will even literally burrow down into most grow mediums and mine juicy aphids from the rhizosphere. However, avoid releasing ladybugs into gardens that have been treated with insecticides or pesticides.

Large infestations, on the other hand, are a little harder to control with biological combatants since they must quickly overpopulate the target pest in order to prevent devastation. In many cases, the time it takes to conquer this feat leaves gardens devastated from neglect.

Azadirachtin extracted from neem, pyrethrums extracted from chrysanthemum, and rosemary and lemongrass oil are naturally derived pesticides that are effective at controlling root aphid outbreaks. These natural plant-based remedies containing rosemary, clove, pyrethrums, and azadirachtin are available to the hobby or commercial grower and feature organic certification. (Organic certified does not necessarily mean safe for consumption, though, so always use care when handling any type of insecticides or pesticides.) I recommend using them together as it provides a broader spectrum of attack against the aphid.

Close up of a colony of root aphids (Trama troglodytes) sucking on dandelion roots.Source: Tomasz Klejdysz/Shutterstock

Different active ingredients will have different effects as far as “kill on contact” is concerned. Rosemary- and pyrethrum-based products should have a more concentrated effect for killing on contact. Azadirachtin will work overtime if applied effectively, but it might have little response as an immediate fix. Also, depending on crop type, age, sensitivity, etc., ingredients will fluctuate as far as effective rate is concerned. For example, you might find that pyrethrums will be more effective on tomato and pepper varietals, but not as effective on roses.

An effective way of applying these products is immersing the entire root system in a premixed solution of the desired active ingredient. I recommend root drenching methods, when possible, for battling root aphids and killing large populations on contact immediately. What to root drench with however, will vary with your personality, preference, interest, and just overall how desperate you really are.

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Basically, using any desired container or reservoir as a holding tank (i.e.: a 5-gal. bucket, a trashcan, etc.), completely dunk rockwool cubes and containers of hydroponic grow medium into solution and agitate with an up-and-down motion. This will help knock off eggs, larvae, adults and anything clinging to the root mass.

Soilless mixes, such as coco and peat, can be irrigated manually until run off for effective application. It’s also possible that you might need to apply a weaker dilution rate of the desired ingredient with hydroponic gardens because they will be more susceptible to more frequent irrigations—as opposed to soilless mixes, which can hold the solution in the root system for a longer period of time. Less is always more; you can always add a little more, but once damage is done, it’s impossible to undo.

For those who must drop the nuke, so to speak, imidacloprid is the answer. This nasty molecule is sheer death to all root-dwelling insects like aphids, thrips and fungus gnats (it pretty much annihilates anything except mites). Different concentrations of imidacloprid are available in different forms. Just be sure to use extreme caution when handling and applying this dangerous compound.

Cleanliness is obviously the best way to prevent problems from occurring in the garden. Always start from seed if possible, and avoid transfer of cuttings in order to prevent spreading root aphid infestations. Great gardeners are susceptible as much as beginner growers, so practice consistency, develop methods and implement follow-through. Despite heat waves and bug swarms, your garden should stay insect- and disease-free with the proper inputs and routine practices.

Read also: Keeping Bugs Off Your Nugs


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Written by Lee McCall

Profile Picture of Lee McCall
Lee McCall is an alumnus of Johnson & Wales University. His extensive culinary background helped him gain experience in and knowledge of fine dining and food production, which developed into a career in the hydroponics industry. Lee and his business partner use their Denver-based businesses to educate the public on sustainable gardening and high-quality produce.

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