How to Identify & Fight Grow Room Pests

How to Identify & Fight Grow Room Pests

Keith
Keith
05 Aug 2011

It's getting warmer and the bugs are coming! By hook or by crook, they’ll try to sneak into your grow room and ravage your plants.

If they break past your first defences, all’s not lost. You can still win the war. Here’s how you prevent, identify and defeat common grow room pests.

Always be on the Lookout

Don’t wait until they've destroyed your plants. Instead, create an ongoing strategy for preventing, spotting and fighting pests.

This is called an IPM (Integrated Pest Management) strategy:

Spider Mites

Spider mites are very common, but easily treated.

Identify

Look out for small, yellow speckles on the top surface of leaves – a sure fire sign that mites have been feeding.

The undersides of leaves may also contain tiny white dots that are either the mites and/or their eggs. Webbing occurs in the latter stages of an infestation.

Combat

 You can use natural predators:

  • Using sachets (preventative): Put 1 - 2 in a propagator, 1 per plant (veg) or 1 - 2 per plant (flowering)
  • Via a bottle (treatment): Sprinkle the contents around your room & leave the opened bottle at the base of plants

You can also use sulphur:

  • Using Hotbox Sulfume (treatment): A 2kg dose of sulphur will treat areas from 2m3 - 10m3 for about a year.
  • Using a Fortefor P Fumer: This'll fumigate aread up to 80m3 (only use between crops)

After eradicating pests, clear off residue and dead bugs by spraying your plants once with water. Then remove damaged leaves and keep temperatures down to slow the rate of spider mite breeding. 

Extensive Damage on a Cucumber Plant Extensive Damage on a Cucumber Plant
Extensive Damage on a Cucumber Plant

   

Infestation on a Cucumber plant Infestation on a Cucumber plant
Infestation on a Cucumber plant
Early Damage on a Hop Plant Early Damage on a Hop Plant
Early Damage on a Hop Plant

   

Extensive Damage on a Hop Plant Extensive Damage on a Hop Plant
Extensive Damage on a Hop Plant
Close up of Spider Mite Adults, Nymphs and Eggs Close up of Spider Mite Adults, Nymphs and Eggs
Close up of Spider Mite Adults, Nymphs and Eggs

   

Spider Mites and Eggs on Webbing Spider Mites and Eggs on Webbing
Spider Mites and Eggs on Webbing

   

Close up of a Two Spotted Spider Mite, a Red Spider Mite and an Egg Close up of a Two Spotted Spider Mite, a Red Spider Mite and an Egg
Close up of a Two Spotted Spider Mite, a Red Spider Mite and an Egg

Thrips larvae

Thrips are most harmful to plants at the larval stage. 

Identify

Search for silvery grey trails along the tops of leaves and small black deposits (their excretion) on the opposite side.

The larvae feed by rasping the leaf surface, leading to distorted growth and loss of colour.

Combat

Take off infected leaves and apply Pyrethrum 5 EC / Protector as a foliar spray. This should eliminate Thrip Larvae in vegetative and early flowering growth. You can also try using natural Thrip Predators or Nematodes.

Malformed Pepper Leaf Caused by Thrips Malformed Pepper Leaf Caused by Thrips
Malformed Pepper Leaf Caused by Thrips

   

Severe Thrips Damage on Pepper Leaves Severe Thrips Damage on Pepper Leaves
Severe Thrips Damage on Pepper Leaves
Thrip Damage on the Top of a Pepper Leaf Thrip Damage on the Top of a Pepper Leaf
Thrip Damage on the Top of a Pepper Leaf

   

Adult Thrips, Larvae & Waste on a Pepper Leaf Adult Thrips, Larvae & Waste on a Pepper Leaf
Adult Thrips, Larvae & Waste on a Pepper Leaf
Thrip Damage on the Underside of a Pepper Leaf Thrip Damage on the Underside of a Pepper Leaf
Thrip Damage on the Underside of a Pepper Leaf

   

Early Signs of Damage Caused by Thrips on a Sunflower Leaf Early Signs of Damage Caused by Thrips on a Sunflower Leaf
Early Signs of Damage Caused by Thrips on a Sunflower Leaf

Fungus Gnats

Fungus Gnats are quite a common grow room problem. 

Identify

You know you’ve got them if you have small, slow moving black flies in your grow room. Yet it’s the larva that upset your plants, eating roots and slowing overall growth.

Combat

Lower your grow room humidity and growing media water level. That’s normally all you need to do.

If not, add Nematodes to the root zone – they’re 100% effective and are bound to do the trick.  

Don’t forget to place sticky yellow traps around your grow room to helps capture the flies and identify the problem early.

Adult Fungus Gnats Adult Fungus Gnats
Adult Fungus Gnats
Fungus Gnat Larvae Fungus Gnat Larvae
Fungus Gnat Larvae
Close up of Fungus Gnat Larvae Close up of Fungus Gnat Larvae
Close up of Fungus Gnat Larvae
Close up of Adult Fungus Gnats Close up of Adult Fungus Gnats
Close up of Adult Fungus Gnats

Leaf Miner

Leaf Miner Larva look similar to Thrip Larva, but they move far more slowly and are less of a risk.

Identify

These tricky little critters live within the leaf itself, so you’re only really likely to notice foliar damage – not the actual larva. Look out for colour loss and leaf imperfections caused by them feeding.

Combat

A good spray of Pyrethrum 5 EC / Protector promises to deal with the problem.

Don’t worry too much about harmed leaves – the vigorous growth rates of plants under HID lights means that they’ll often outgrow any damage. 

Leaf Miner Damage Leaf Miner Damage
Leaf Miner Damage
Leaf Miner Damage Leaf Miner Damage
Leaf Miner Damage
Leaf Miners on a Plant Leaf Miners on a Plant
Leaf Miners on a Plant

Aphids

Aphids feed on new vegetative growth and flowering sites. They suck up the sugary liquid from the phloem tissues using a straw-like proboscis (elongated nose or snout).  

It’s startling how quickly they can lay eggs and grow. And they munch up masses of plant material, maiming your leaves and stems. If left untreated, eventually your plants will die.

Identify

Watch out for leaf and stem deformities. You might also spot drops of honey dew on leaves – a waste product that aphids shed onto lower leaves. Eventually, this sticky substance changes into a black sooty mould.

Combat

Cut off the most infected parts of the plant, including many of the new flowering sites. Then use a decent insecticide spray, such as Pyrethrum 5 EC / Protector.

Aphids on Pepper Leaves Showing Distorted Growth Aphids on Pepper Leaves Showing Distorted Growth
Aphids on Pepper Leaves Showing Distorted Growth
Aphids on Pepper Bud Aphids on Pepper Bud
Aphids on Pepper Bud

   

Cabbage Aphids with White Wax Coating Cabbage Aphids with White Wax Coating
Cabbage Aphids with White Wax Coating
Aphid Skin Moults on Hop Leaves Aphid Skin Moults on Hop Leaves
Aphid Skin Moults on Hop Leaves

If you're currently suffering from a bad infestation and the pests in question don't match up with any of those above, give us a call, start a live chat or visit your local store for more advice.


Featured Products


Keith
Keith
About the author

Keith looks after our stock and staff. He's a bit of a hippie and has the hots for chillies. If you want to grow them, ask Keith how it's done.

Head Office

Order Online:
0333 003 22 96