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Stop Root Aphids From Harming Your Marijuana Plants! expert marijuana growers offer great service to the marijuana growing community by answering questions from growers just like you.

This article deals with an increasing pest problem in the marijuana growing community: root aphids.

Question: My cannabis plants are getting whacked by infestations of root aphids. I did some searching and have obtained Gnatrol but hesitate to use it in my hydroponic system because I worry that it could pollute my plants. What ideas do you have to help me?

Best regards,


Up until about 15 years ago, marijuana growers didn’t have problems with root aphids, except in rare outdoor cannabis growing situations.

Nowadays, aphids and root aphids seem to be plaguing more and more marijuana gardens.

The first thing to wonder is, where the hell did these little bastards come from? One answer is: commercial soil.

For people growing indoors with tight vector controls who don’t import clones into their grow ops, soil is pretty much the only way any root zone pests can get into their crop’s root zone.

I won’t be so cruel as to name the specific national soil brands that are known to contain root aphids, thrips, and other pests. Ask your hydroponics store or other marijuana growers and you’ll find out.

But know that an ounce of prevention is worth a pound of lost bud production when it comes to soil-borne pests and diseases.

Only buy clean soil!

Gnatrol is specifically designed for fungus gnats, not root aphids. For marijuana plants suffering from a root aphid infestation, some marijuana growers have success using Azatrol, predatory nematodes, mosquito dunks, or Azamax.

On those marijuana grower forums that are often the source of really bad, albeit well-meant advice, you’ll see all kinds of wild, crazy, and harmful suggestions for how to deal with root aphids and other soil problems.

Some of the bad advice includes using horticultural soaps or even detergents.

Horticultural soaps are good at trashing some marijuana pests when you use the soaps as a foliar spray, but in the root zone the soaps can coat the roots and interfere with soil porousity, pH, and water transfer to the roots.

I’ve also seen geniuses on forums like who recommend grinding up onions and garlic, combining it with neem, cinammon, and other crap, and drenching the roots with it.

Again, not a good idea, not even close.

One lesson is: disregard much of the advice you find on grow forums. Most of it is guesswork. Or at least be cautious about applying the advice you see there.

How does a cannabis grower even know they have root aphids to begin with?

It starts with daily monitoring of your marijuana plants. If you notice stunted growth, leaf problems associated with nutrients deficiencies, lower than average water use, stem damage just above the soil line, ants, or you can see active aphids in the soil…immediately do a preventive or fixative drench using a safe product like Azamax, even in bloom phase.

If you verify a root aphid infestation, your first action is to get rid of them from your root zones as best you can.

Just know that you might not get 100% removal. That means you have to trash those plants after harvest.

Only in the most extreme cases, such as when you have the world’s most valuable marijuana motherplants, do you want to risk keeping insect-infested cannabis plants in your garden past harvest time.

Not only that, but after harvest you do extreme sterilization of anything and everything in your irrigation and grow space that has any possibility of coming into contact with your marijuana plants.

In outdoor marijuana growing, you can try Azamax or the other remedies, but you’re often fighting a losing battle because if aboveground aphids or root aphids are thriving outdoors where you’re growing your marijuana, they’ll keep coming back.

My fundamental advice is, don’t let root aphids come into your garden. Grow indoors using pure hydroponics, or absolutely clean soil. That’s what’s best for your marijuana plants!

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