By Luke Sumpter

Your hydroponic grow tent might feel like a safe haven; you’re in complete control of the light cycle, temperature, and nutrient schedule. But don’t get complacent. Hydroponic growers also have to deal with pests. While bothersome insects are more prolific outdoors, they often wriggle, fly, and crawl their way into indoor growing operations too. Even if you’ve taken special care to secure your windows, vents, and other possible entrances, pests can enter via a host of vectors, including growing equipment, clothing, and growing media.

Identify and Eliminate Cannabis Pests From Your Hydroponic Grow

So, what exactly are you up against? Given the chances, many different pest species will "champ at the bit" to sink their mouthparts into your luscious cannabis leaves, stems, and roots. But six species, in particular, are much more successful at penetrating hydroponic cannabis setups and making a meal of plants.

Below, you’ll learn everything you need to know about these critters, including how to identify them and how to banish them from your cultivation space.


These minute sap-sucking insects target the xylem, or vascular system, of plants. These internal tubes ferry water and dissolved nutrients throughout the plant. Aphids use their mouthparts to puncture plant tissue and siphon this precious liquid.

A handful of aphids can satisfy their needs without doing too much harm, but they multiply fast. When their numbers get out of control, they can quickly suck a plant dry. Without enough circulating nutrients, hydroponic cannabis plants become stunted and deprived. There are around 5,000 species of aphids, and each one generally targets a particular plant species. The hemp aphid (Phorodon cannabis) has a ravenous appetite for, well, cannabis sap.

What Cannabis Leaves Can Tell You
How To Spot Aphids
Cannabis aphids aren’t very subtle in their approach; they leave obvious signs as they go about sucking on sap. Perhaps the most obvious is the aphids themselves! These pests congregate on the stems and leaves in large numbers, and primarily amass on the underside of fan leaves to shelter themselves from direct light. Other signs of aphids include:
  • White skin moults on leaves
  • Sticky sap buildup on leaves
  • Stunted growth
  • Yellowing leaves
How To Treat Aphids
So, how should you proceed in eliminating aphids from your hydro grow? Check out the most effective methods:
  • Defoliate: Use a pair of pruning shears to cut away severely infested branches and leaves.
  • Organic insecticides: Use organic insecticides, such as Essentria IC3 and Spinosad, according to the product instructions.
  • Neem oil: Mix 1 teaspoon of neem oil and 4–5 drops of surfactant into 1 litre of warm water, and apply with a misting bottle directly to affected sites.

Root Aphids

Root aphids aren’t dissimilar to their above-ground cousins. Instead of sucking sap from leaves and stems, though, they target the roots. However, the life cycle starts on the aerial parts of the plant. Once the eggs hatch, these critters migrate downward. Yes, root aphids also impact hydroponic cannabis plants!

What Cannabis Leaves Can Tell You
How To Spot Root Aphids
Root aphids are easier to spot when growing hydroponic cannabis. While soil growers can’t peer into the rhizosphere, hydro growers can take a direct look at the root system. Here’s what to look for:
  • Tiny white critters in the root network
  • Chalky white material on roots
  • Stunted growth
  • Wilted leaves and loss of plant vigour
How To Treat Root Aphids
In order to eliminate root aphids in hydro, in coco, or in Rockwool, you have to be aggressive, but cautious:
  • Killer dip: Prepare a bucket of insecticidal soap solution. Pick up plants by the net cup, then dip the roots into the solution, followed by a dip in a rinse bucket.
  • Clean: After removing the plant, thoroughly scrub down your hydro bucket with a 3% hydrogen peroxide solution.

Spider Mites

Spider mites often show up in hydroponic cannabis grows. As a species of mite, the “spider” in their name merely refers to the silk webs they spin in order to protect their colonies from predators. These tiny pests hang out on the underside of leaves, frequently piercing plant tissue to feed on cells. Once a spider mite colony achieves a respectable size, it can do some real damage.

What Cannabis Leaves Can Tell You
How To Spot Spider Mites

Fortunately, spider mites leave tell-tale signs that make them easy to spot before they develop a substantial foothold. Look out for:

  • Spider mites themselves
  • Webbing
  • Eggs, which appear as tiny white specks
  • Stunted growth
How To Treat Spider Mites
Once you discover the presence of spider mites, don’t hang around! Use the tips below immediately to deal with the infestation:
  • Reduce the temperature: Spider mites like it warm, so try to maintain a consistent temp of 20ºC in your hydroponic growing space.
  • Prune: Chop away leaves and branches that are completely overrun with webbing and eggs to minimise further spread.
  • Predatory insects: Introduce beneficial insects such as ladybugs into hydroponic greenhouses and polytunnels (they’re less suitable for indoor situations, as you can imagine).
  • Insecticidal soaps: Apply insecticidal soaps to the affected area in line with product guidance.

Fungus Gnats

Although they’re pests in the eyes of hydroponic cannabis growers, fungus gnats play a crucial ecological role. They feast on fungi in the soil, contribute to the decomposition of organic matter, and even carry pollen and fungal spores. Despite their vital function, fungus gnat larvae have a habit of damaging cannabis root hairs, and the adults carry diseases, such as “damping off”, that kill seedlings.

What Cannabis Leaves Can Tell You
How To Spot Fungus Gnats

A fungus gnat infestation is generally easy to identify in a hydro cannabis grow:

  • Gnats crawling and jumping around the root system
  • Maggots wriggling around the root system
  • Pale, spotted leaves
  • Brown edges on leaves
  • Drooping plants
  • Collapsing seedlings
How To Treat Fungus Gnats

How to go about killing fungus gnats in hydroponics? Consider these options:

  • Yellow sticky traps: Place these contraptions close to your hydro buckets and reservoirs.
  • Beneficial bacteria: Apply a solution of Bacillus thuringiensis israelensis to the root system to send fungus gnats packing.


Another sap-sucker, whiteflies also dwell on the underside of leaves. After dining on sap, they excrete a sticky substance that accumulates and attracts other pests and contributes to the growth of moulds. Whiteflies can work their way through vents, or simply fly through open windows and doors, and lay their eggs in circular groups of 30–40 on cannabis leaves.

What Cannabis Leaves Can Tell You
How To Spot Whiteflies

Much like aphids, whiteflies puncture cannabis tissue and drain out sap, which leads to a list of similar symptoms. The primary signs of a whitefly infestation are:

  • Whiteflies buzzing around cannabis canopies
  • White groupings of eggs on the underside of leaves
  • White spots on top of fan leaves
  • Yellowing leaves
  • Loss of vigour
How To Treat Whiteflies

Are whiteflies taking a toll on your hydroponic weed plants? Use these tips to get rid of them as soon as possible:

  • Predatory insects: Ladybugs also have an appetite for whiteflies; deploy them in greenhouses and polytunnels.
  • Wipe them away: If you’re only dealing with one or two infected plants, use a damp cloth to remove any eggs, and discard them away from your growing space.
  • Neem oil: Our trusty old friend neem oil also comes in handy here; apply a diluted solution with a mister.
  • Essentria IC3: Apply this mix of horticultural oils according to product instructions, and use daily until the infestation ceases.


Thrips love the conditions of indoor growing environments. The controlled temperatures, consistent lighting, and abundance of water in hydroponic setups is a haven for these creatures. Surprise, surprise—thrips also have a penchant for cannabis sap. Think about it. This rich substance contains all of the nutrients plants need to survive. Why wouldn’t they tuck in?

But thrips don’t just pose a direct physical threat to your hydroponic cannabis plants. This pest also carries over viruses that cause plant disease. You don’t want them anywhere near your indoor grow.

What Cannabis Leaves Can Tell You
How To Spot Thrips

Your plants are looking worse for wear. How do you know you’re dealing with a thrip infestation? Look for these key signs:

  • Distorted leaves
  • Curls, rolls, or folds on leaf tissue
  • Irregular bronze and silver spots
  • The presence of thrips themselves—small yellow-white flies with or without wings depending on their stage of life
How To Treat Thrips

Got thrips? Don’t let this pest do any further damage. Take these measures to get the infestation under control and rescue your hydroponic grow:

  • Sticky traps: Suspend sticky traps from the top of your grow tent so they dangle in close proximity to the canopy.
  • Neem oil: Apply a diluted neem solution and let this plant oil works its magic once again.
  • Alternative sprays: Pyrethrum fatty acids and plant oil products are great options to get rid of thrips.
  • Predatory insects: Deploy predatory mites, such as Amblyseius, Hypoaspis, and Macrocheles, in greenhouses and polytunnels.

Pests Threatening Your Hydro Grow? — Go on the Offence!

There you have it; now you’re equipped with the knowledge to defend your hydroponic cannabis plants against the six major pests that are out to get them. Remember, just because you’re growing in a cosy indoor setting doesn’t mean these critters won’t find a way in. Make an effort to keep your space clean, and regularly inspect your plants and hydroponic system for issues. The earlier you detect the signs of an infestation, the better the odds of saving your precious plants.

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