Summer is almost upon us. The time of year that indoor growers hate the most! Not only for extra heat getting in the way but also for the myriad of pests that will try and gain access to your indoor garden of Eden.

If there is one thing that will make any indoor grower pull his hair out, it is an unnoticed infestation of pests in their garden. Whilst the little critters may not have the brazen criminal genius of Kyza sozey, what they lack in brain smarts they more than make up for in numbers and persistence, a bit like the kids in ‘City of God’. The best way to combat pests is to understand them, and know their typical signatures. Taking a leaf out of Sun Tzu’s Art of War, you need to know your enemy if you want any hope of defeating him/her. Fear not diligent reader, Hydromag is here to give you all you need to know about the main few little sods that you will encounter in your grow room, and how best to go about getting rid of them. The following pages will serve you well as a reference point to identify exactly what it is that has infiltrated your inner sanctum, and what steps you need to take to eradicate them. The Law Enforcement Team


Spider Mite

Vital Stats

  • Habitat: Underside of leaves
  • Preferred Conditions: Hot and Dry – 25-30C and <55% RH
  • Egg hatch time (25C/55%RH): 4 Days
  • Egg to Adult (25C/55%RH): 9.5 Days
  • Total Eggs laid per female (25C): 130

How to recognise Spider Mites?

1. Early Leaf Damage

The early signs of spider mites can be spotted by the damage they cause when feeding on the underside of the leaf. The white dots that appear like pin pricks on a leaf it is a sign they are setting up camp and planning an invasion.

2. Late Leaf Damage

As the mites feast away on the leaves the damage develops to causing significant yellowing and even necrotic patches.

3. Webs

A mature colony of spider mites will start to spin webbing for use as rapid transport between leaf structures, and even between plants. You can see in the pics they will lay eggs on the webs too.

4. Mites

When you spot the early symptoms and turn the leaf over, you will be able to see the tiny insects with the naked eye and even better with a magnifier. There are two main types of spider mites; the two-spotted mite and the red mite. The two-spotted is more common and when you look up close you can see its beige coloured body with two clear spots on its back. The red mite is more of an orange-red colour.

5. Eggs

If you have a keen eye you will also be able to see the eggs they lay, which are tiny round balls between 0.1-0.2mm in diameter. These start transparent in colour and turn an opaque milky colour before a yellow straw colour when ready to hatch. Spider Mites

How to control Spider Mites?

Spraying will combat mites well. Follow the labels carefully with chemical sprays. For contact spays that work by physical modes of action it is good to spray every 3-4 days in order to kill the young mites emerging from the newly hatched eggs. Being diligent with your sprays by coating both the top side and underside of the leaf as well as the whole plant is a must, particularly with contact sprays. Predators are successful where you spot the problem early and if you can keep temperatures down and humidity up. Spraying to get the upper hand, then introducing predators is a good approach.

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Spider Mite SMC+ Control- Buy it

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Vital Stats

  • Habitat: Underside of leaves
  • Preferred Conditions: Hot and Dry – 25-30C and <55% RH
  • Egg hatch time (25C/55%RH): 3 Days
  • Egg to Adult (25C/55%RH): 13.5 Days
  • Total Eggs laid per female (25C): 1

How to recognise Thrips?

1. Early Leaf Damage

The feeding damage by Thrips to the underside of the leaf causes small silvery patches to develop which can be seen on the top side. Many people say the early damage can appear like a tiny section of a shiny slug or snail trail. You can see from the pictures you have to have a keen eye to spot this damage.

2. Late Leaf Damage

As the Thrips feed from the leaf you may see leaf distortion as well as small patches of yellow and brown as the leaf cells die (A). As this point you will be able to see the Thrips clearly when you turn the leaf over (B). As the Thrips feed and the damage spreads large leaf areas may develop yellow/white patches. You will also be able to see tiny black dots among the feeding damage, this is the thrips poo.

3. Thrips

These pests are fairly easy to spot, and have two distinct observable life stages; the larval stages and the adult. The larvae of Thrips appear as tiny beige coloured maggots around 1mm in length, but when you look up close you can see their legs and antennae. They live mainly on the underside of the leaves and when disturbed they like to hide out at the leave veins. Thrips larvae will eventually pupate into an adult and the pupa can often fall onto the surface of the growing media.

4. Eggs

Thrips lay their eggs inside plant tissue, and can been seen in some crops as tiny bumps on leaves, but are often very difficult to see at all. Thrips will also crawl into flowers and buds, and lay eggs on soft tissue, flower petals and even soft parts of stalks. Thrips

How to control Thrips?

Spraying foliage regularly to kill both larvae and emerging eggs is recommended for sprays that work by contact. If you can spray every 3-4 days for 2 weeks you will gain control of the situation. Adults are difficult to kill without chemical sprays, so disrupting their life cycle by killing the larval stages and eggs works well. The predatory mites Amblyseius cucumeris are great at controlling small populations as these mites eat the larvae and stop population explosions. Predatory mites generally need higher humidity and long day lengths to function well so establishing them in vegetative growth is a good approach.


Some growers see small insects jumping about on the surface of the growing media or on the surface of water in saucers or reservoirs and think they are Thrips. These insects are actually Springtails and are relatively harmless. Adult Thrips are darker in colour and appear brown or black and get up to 1.4mm in length. The adults fly and can move from plant to plant within a grow room very quickly. There are many species of Thrips but the main culprits of indoor crops are the Western Flower Thrips.

Shop online:

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Fungus Gnat aka Sciarid Fly

Vital Stats

  • Habitat: Root Zone
  • Preferred Conditions: Moderate and Moist
  • Egg hatch time (25C): 5 Days
  • Egg to Adult (25C): 21 Days
  • Total Eggs laid per female (25C): 100-300

How to recognise Fungus Gnats?

1. Early Signs

With fungus gnats, you do not often see any plant symptoms early on. The most common first sign is seeing the tiny black flies buzzing about. They are slow and easy to squish in the air by clapping your hands. By using yellow sticky traps you can see quite quickly the extent of your problem. The flies like wet soil and coco, so leaving the traps on the tops of pots will catch some pretty quickly if they are about.

2. Fungus Gnat Larvae

As you can see by the pictures, these are little 5-12mm long white-translucent maggots with a black head, and these are the main problem. The adults fly around rather annoyingly, and lay eggs on the growing media. The larvae hatch and feed on whatever organic matter is available, but they love roots. If you can see fungus gnats buzzing about and you look closely at your growing media surface, or on rockwool blocks, you will most likely find some larvae. With rockwool, they are attracted to algae that grow on the surface, and with soil and coco they are more attracted to pots that are constantly damp or wet. Fungus gnat larvae can do considerable damage to plants by destroying the root system, particularly young plants with relatively little root mass. A common indirect effect of the larvae eroding the root system is the spread of disease. The larvae are vectors for fungal pathogens, and when they munch on the roots they are opening up tissue ready for invasion. Fungus Gnats

How to control Fungus Gnats?

The adult flies only survive for up to 7 days but can the females lay up to 300 eggs so it’s vital you do your best to catch or kill these. The easiest was is by using yellow sticky traps positioned near the pots. However, all the damage is being done in the root zone so this must be your target area. There are root drenches that can be used containing various ingredients that kill the larvae, use every 5 days to ensure you kill the newly hatched larvae. Predatory insects are excellent for fungus gnat control. The nematodes packs are very effective and last up to 6 weeks and the predatory mites Hypoaspis miles are very efficient as a preventative as well as treatment.

Shop online:

A.R.T.S Fungus Free - 250ml - Buy it

ProActive Boost & Fungicide Effect - 1L - Buy it

Aptus Fungone 1L - Buy it

Spray2Grow Concentrate 500ml - Buy it


So there you have it, now you are armed with the necessary brain smarts to deal with pests in the correct manner, choose your method of attack wisely! The ultimate key to a pest free environment is preventative measures: Bug meshes on intakes, change your clothes when entering your room, clean your room thoroughly between grows and possibly most importantly scrutinise/quarantine any clones you are (un)fortunate enough to have received. Measures like this in keeping your room squeaky clean will help to ensure you’re not starting a fight on the back foot. Essentially you want to aim for a room that would make Howard Hughes proud. Thanks go to HydroMag for allowing us to publish the article, you can also check out the entire magazine online HERE while treatments to help get your grow room pest free are available on our online store at HERE.