Hydroponics can be a rewarding and educational experience. The crop yields are generally much higher than conventional methods and require less space. One of the problems with gardening in general however is dealing with pests and disease.  

Hydroponic gardens are prone to disease and insect or pest invasion just like conventional farming, only with a few slight differences… 

Since hydroponic gardens are normally self contained, and cut off from the outside world, they’re actually far less prone to contracting an insect, fungal, or bacterial pest or disease.  

The problem however, is that if one of these organisms finds its way into the garden, it lacks the competition found in nature to keep it in balance. A small pest invasion will quickly take over and destroy a crop if left unchecked in an indoor hydroponic garden.  

Knowing how to deal with plant pests and disease is crucial if you want to see success in your indoor garden.  

Common Insect Pests

The same insect pests that affect outdoor gardens will affect indoor ones. Thrips, spider mites, nematodes, aphids, fungus gnats, and mealybugs are all common outdoor AND indoor garden pests.  


Thrips are small, greenish black insects that move at lighting speed and tend to jump off your plants leaves whenever you try to look for them and as a result they are rarely seen. Identifying thrips relies more on finding the damage they cause than seeing the insect itself.  

Thrips will use special mouthparts to scrape away the surface of the leaves in order to get to the sugary, juicy insides. The leaves will look scaly, and silver. Large infestations will start to cause growth defects in the leaves, and older leaves will begin to die off.  

Thrips are best dealt with by blocking off the roots of your plants with plastic. Part of their life cycle involves dropping off into the root zone to grow as larvae before crawling back up the plant to feed on the leaves. Blocking off this crucial stage in their life cycle is one of the simplest and most effective ways to eliminating thrips from the hydroponic garden. 

Spider Mites

Spider mites are in the arachnoid family, and can actually spin webs just like a spider. These tiny insects are hard to see with the naked eye, but will form large colonies quickly which are shrouded in web structures which they use as highways to get from leaf to leaf. These webs protect them from sprays and help to create a small microclimate for their eggs. 

Spider mites need to be attacked vigorously and early. Use insecticides containing neem, malathion or pyrethrum for best results and repeat every 3 days until they are completely gone and monitor closely for signs of their return or remission.  

Mealy Bugs

Mealybugs are white, fluffy looking insects that attach themselves permanently to the leaves or stalks of your plants, where they spend the rest of their short lives sucking the sugary juices from your plant.  

Mealybugs are very difficult to treat because their hard shells protect them from being exposed to insecticides. They reproduce quickly, and will feed on a wide range of plant species.  

The best way to manage mealy bugs is to use pyrethrum insecticides to target the younger generations that lack the hard protective shells and to attack adults individually with a cotton swab soaked in alcohol. This is tedious, but one of the most effective ways to deal with mealybug infestations.  

Fungus Gnats

Fungus gnats are tiny flying insects. Although they are not a huge danger to your crop, they multiply very quickly, and are an annoying pest to have around. They tend to accumulate in the root zone of plants because this is where they lay their eggs. The eggs hatch and begin feeding on your plants roots before maturing and flying away to lay eggs of their own.  

Dealing with fungus gnats involves blocking off the root zone with plastic or a layer of sand, and spraying heavily infested plant roots with a mixture containing pyrethrum.  


Aphids are great pioneers. When colonies grow large enough, they begin producing offspring with wings, which they use to fly to other areas in search of new food sources. Once they find a new spot (which may be the inside of your hydroponic garden) they only need a single insect to start a colony. Aphids don’t need a male and a female to produce young, and are often found to be born already pregnant. This makes it very easy for them to grow incredibly large colonies from a single insect.  

Aphids have soft swollen bodies, making them easy to kill by either pinching them with your fingers, or through insecticide use. Their rapid reproduction and large numbers are what makes them difficult to eliminate completely.  

The best way to manage aphids are to attack them with insecticides aggressively, following up with treatments every 3 days. Even when no more aphids can be found, it is wise to continue the treatment for up to a week paying special attention to the new growth on your plants, and the undersides of leaves where they tend to hide. 

Common Diseases In Plants

Powdery Mildew

Powdery mildew is a fungal disease affecting the leaves. It’s very common in indoor gardens, especially areas with poor airflow, and cooler temperatures. You can identify powdery mildew from the dusty, fuzzy appearance it leaves on infected areas. Powdery mildew will not grow on anything but leaves, so if you find something that fits this description in the soil, it is something else.  

Treating powdery mildew is generally quite easy. Antifungal agents can be sprayed onto the affected areas and generally result in the complete elimination of the fungus after just a single treatment. Sometimes a follow up treatment or 2 will be needed. Once eliminated, it can help to increase the airflow of your hydroponic garden by adding circulation fans or adjusting current ones. With high airflow, powdery mildew doesn't have the opportunity to reproduce and grow on your plants.  


Pythium is one of the worst common diseases you will face in your garden. It is a fungus-like organism that infects the roots of your plants. It’s both highly infectious and lethal.  

The best treatment for this disease is prevention. Ensuring that there are no\ dead or rotting roots in your system, using enzymes or hydrogen peroxide.  

Changing the water regularly, and making sure it remains in constant motion with air stones, and water pumps will go a long way in preventing pythium infection in your garden as well.  


Knowing what can infect your plants, and how to identify them make it much easier to find a solution to the problem. All of the pests and disease discussed in this article are very common, and at least one of them is likely to be faced by any hydroponic gardener no matter how many precautions you take. This is why regular inspections of your plants is crucial if you want to catch these infections early and deal with them long before they become a problem. 

Check out our supply of pest control products and consider keeping some on hand before the problem occurs. This way you will have all of the tools needed to treat the problem quickly without having to run out to the shop when an outbreak occurs. We recommend keeping something with pyrethrum on hand, and some enzymes to prevent pythium in the very least.