How to Detect, Prevent & Kill Root Aphids in Your Marijuana Garden

Root aphids are a hidden but increasingly big problem in marijuana gardens indoors and outdoors. Here’s why you need to do everything you can to prevent them from visiting your gardens:

• Root aphids most often operate invisibly, hiding in the root zone, so you have no idea they’re at work destroying your roots, although they sometimes travel aboveground too.
• Root aphids work fast and can damage or totally destroy roots within a few days.
• Symptoms of root aphid infestations often look exactly like nutrients problems, root rot, and other problems, leading you to misdiagnose and mistreat the actual problem.
• Root aphids evolve so quickly that they develop resistance to pesticides even during the crop cycle when pesticides are being used.
• Root aphids can travel from the root zone to the green parts of your marijuana plants, and from plant to plant. The photo at the top of this article shows root aphids that have traveled up the plant. Note that they’re much lighter than regular aphids, which are most often orange-colored.
• Root aphids often have a whitish chalky coating that armors them against organic and natural pest control methods.
• It’s hard if not impossible to totally eliminate root aphids while infested plants are still growing.
• Root aphids are often found in commercial potting soil or soilless mixes sold in hydroponics and gardening stores.
• Root aphids do damage that makes your cannabis plants more susceptible to stress, other pests, and to diseases like Pythium and fusarium wilt.

How do you know if root aphids are present in your marijuana garden? Here’s how…

• If you see suddenly-wilting or yellowing leaves, especially on entire branches, while other branches look healthy, this is often a sign of root aphids. Problems that look like nutrients issues may also be caused by root aphids. Take a look at the picture of the bud in this article, which is showing symptoms of root aphid infestation.
• If there’s a chalky, powdery substance at the top of your root zone, that can be a sign of root aphids.
• If you have yellowing, wilting or otherwise defective leaves and the problem hasn’t been fixed by adjusting nutrients, pH, root zone moisture levels, lighting, and grow room environment, you might as well treat the plant for root aphids.
• If you see black, sooty mold on stalks or stems, or at ground level where your plant’s main stalk emerges from the ground, that’s often a sign of root aphid infestation.
• If you see flying pests that are the same size as and look kind of like fungus gnats, but aren’t fungus gnats, those could be mature root aphids, which sprout wings and fly at one stage in their life cycle.
• If you see what looks like regular aphids but they’re lighter in color and in the root zone or the green parts of your plants, those could be root aphids.
• If your plants are properly fed, the grow environment is correct, and you’re providing the right type and intensity of light, but your plants aren’t using much if any water and are growing slowly or look sick, your plants might have root aphids.

If you suspect root aphids, here’s how you can be more sure that root aphids are present…

• Make sure your nutrients solution pH and nutrients feed program are correct.
• Flush your root zone first with a hydroponics flushing solution. Then wait a day or two and flush it with a solution containing 2 ml of 35% strength hydrogen peroxide (H202) per gallon of water. Hydrogen peroxide flushing kills ALL microbes in the root zone, including beneficial microbes. It heals wounds, kills infections, oxygenates the root zone, and can damage or kill some marijuana pests. Test your hydrogen peroxide treatment on one plant first, so you can see if the dosage is too high, and be sure not to get food-grade H202 on your skin or anywhere else on your body—it can burn you.
• If you’re growing in pure hydroponics such as deep water culture, pull the plants out of their buckets, tubes or other enclosure and examine them closely with magnification.
• If you’re growing in soil or other material and you have a marijuana plant that’s doing so poorly that you don’t care if it survives or not, pull it out of its pot, and examine the root zone with a magnifying glass under strong light.
• Take a look at the green, above-ground parts of your marijuana plants. Root aphids sometimes climb upwards to eat leaves and buds and when they do so, they often look different than regular aphids.

How to Treat Plants to Get Rid of Root Aphids

In most cases, if I suspect aphids of any kind, I treat the entire plant from top to bottom. This means a thorough foliar spraying with a product meant to kill root aphids, mites, mealybugs and other pests. It also means I treat the root zone. Unfortunately, there are very few all-natural or organic materials that effectively kill aphids in the root zone or the green parts of your plants. Root zone aphids are especially hard to kill using non-chemical insecticides.

Further, it’s hard to find a contact insecticide that works perfectly, because root aphids are protected in the root zone by the zone’s structure. Even if you had a powerful liquid or other material that could kill root aphids on contact, unless you pour so much water into your root zone as to cause waterlogging that harms roots, it’s hard to kill every root aphid. And if you don’t kill every root aphid, watch out, because they can come roaring back to full infestation within a couple of days—that’s how fast they reproduce.

Growers whose plants are in individual pots using solid root zone media such as rockwool, soil, soilless mix or coco coir sometimes get a container much larger than the pots, fill it with a horticulturally-safe insecticide solution, place the entire plant pot into the container, and thoroughly soak the root zone by immersion.

Growers using aeroponics, deep water culture and nutrients film technique pure hydroponics have a much easier time of successfully delivering aphid-killing compounds to their roots, because the aphids have nowhere to be except on the root. There’s no soil or other material for them to hide in.

The aphid-busting program that’s worked best for me is the following multi-step process…

• First, I ensure that marijuana grow op problems I’m seeing aren’t caused by faulty nutrients, bad pH, bad environment, non-aphid pests, or root zone diseases.
• Then I treat the root zone with H202. This harms root aphids, and also kills off pathogens and infections caused by aphid damage, overwatering, and other root zone problems.
• Two days after the H202 drench, I treat the root zone with Imidacloprid, the most effective systemic anti-aphid chemical I’ve found. This compound is usually very expensive, but the product Dominion 2L contains a high percentage of Imidacloprid, and is the least expensive formula containing that compound.
• Note that Imidacloprid is a systemic. It doesn’t always kill on contact. Instead, it’s taken into the plant via roots and kills the aphids when they feed on root and other plant parts. Dominion can take several days to start working.
• I wait until the root zone has dried out, and then do another watering with Dominion 2L.
• Before, during, and after the root treatment period, I foliar spray the aboveground part of the infested plant with Southern Ag’s Naturalyte. Sometimes I instead treat the root zone or foliar spray with Southern Ag’s pyrethrin product. In both cases, it appears to me that these products work to deter root aphids, mites, and other pests.
• I wait a few days, then do another Dominion root drench, and another aboveground foliar spray.

After this lengthy set of procedures, I monitor my infected plants carefully by looking at the root zone, stems, stalks, leaves, and buds with an illuminated magnifying glass. You have to keep a close eye on your plants and their root zones because root aphids are hard to get rid of. They have a remarkably robust life cycle, popping out tens of thousands of new root aphids every day. They armor themselves with a chalky coating that makes it far harder to kill them than to kill regular aphids, spider mites, thrips and other marijuana pests.

In fact, root aphids are often so armored that they may look like mealybugs (scale). Even after an aggressive kill program, root aphids can hang on and start to proliferate again. Sometimes they exit out the pot drain holes of a treated plant to go to untreated plants, to circulate in a hydroponics reservoir, and otherwise travel in hopes of avoiding whatever you’re doing to kill them.

This above-mentioned series of interventions has worked to almost-totally knock out root aphids and above-ground aphids so I got adequate harvest weight, quality, and potency from plants that would have otherwise been rendered useless by aphid infestation.

How Do Root Aphids Get in Your Marijuana Garden?

Many growers including me have wondered how root aphids get into our marijuana gardens. One way they come in is through tainted soil, soilless mix, coco coir and other substrates. They also can live on used pots, and have even been found feeding on the roots of clones in rockwool cubes. Of course, whenever you’re thinking of procuring clones or older plants, be sure to examine the plants and their root zones first. Many pests and diseases transfer can transfer into your garden via externally-made clones. And outdoors in most parts of the world, root aphids are among the many pests that can attack cannabis.

Marijuana grow rooms that are too hot, where pets come in, where there are leaks around windows or via air conditioning and exhaust fans, or where poorly-made or insufficiently-quarantined soil containing pests is used provide vectors for root aphids and regular aphids.

Before I tried H202 and Dominion, as always I tried “safer” interventions including Neem, various plant-based extracts, beneficial nematodes, Azamax, and aphid predators. None of them worked well, and Neem oil created a gooey mess that damaged my plants’ roots.

If your marijuana plants are infected with root aphids, do everything you can do get rid of the aphids. Sometimes, it’s too late. You have to trash those aphid-infested plants and get them immediately out of your grow room or outdoor garden. Get rid of all infected plant material and all material in the root zone; dump it far away from where you grow.

Treat your pots, hydroponics irrigation equipment and other growing gear with chlorine bleach, and carefully inspect all of it before you ever use any of it again. Close up your indoor grow room and set off a few pyrethrin bombs.

Inspect root zone media at the store, before you buy it and bring it home. If you buy clones, carefully insect them, and dip their root balls, rockwool cubes or whatever else they’re rooted in in a mild Dominion solution before you bring them into your marijuana growing area.

Root aphids (along with russet mites) are two devastating marijuana pests that have only become a major problem for growers everywhere in the past ten years. Many of us have spent major time and money treating what we thought were nutrients deficiencies, root rot, and other assumed problems, never suspecting that root aphids were the real problem. Now you’re armed with the information you need to fight and hopefully defeat these resilient, persistent, hidden crop-destroying aphid monsters.