Cannabis Pests

Written by J.C:.Stitch and edited by the excellent Ed Rosenthal, this book is a godsend as a reference work. Its full of useful photos which is what you need when trying to diagnose what’s wrong with a sick or unhealthy plant.

Hopefully you won’t ever need it (although the fact that you are reading this post suggests you may do!) but when you do, its a great help.

Worth buying for its clear information ..  and because when you really need it, this book may save your garden

Some common pests that effect cannabis:



There are many small – and not so small – animals that will happily destroy an outdoor grow: deer, rabbits, armadillos in the

southern US states, goats, even – and often – domestic dogs and cats (the cats will eat leaves in the same way as they sometimes chew grass to aid digestion, dogs it seems are just nosy and will dig where its owner waters!).


The best defence is a 1m high circle of chicken wire and stakes around each plant, but this can be expensive and also obtrusive as it shouts: “I’m worth protecting”.

Other deterrents work by smell and are usually foul: home-made mixtures of human urine, cayenne pepper and so on. Your local garden store or farm shop may well have specific mixtures for sale against e.g., mice as these mammals attack all crops, not just yours.

Spider Mites


One of the most common cannabis pests to hit both indoor grow rooms and outside plants, spider mites cause extensive damage and can be very difficult to get rid of.

You may need a magnifying glass to spot these as the adult is only 0.4mm long, but they leave a fine web which you may see after a fine misting with water. The spider mite’s mouth bites the individual plant cell, ingesting the sap and leaving a brown dead cell. With ever larger infestations, the brown spotting joins up to make a mosaic bronze effect and leaves soon die off. With enough spider mites per plant – and reproduction rates are high – before long the whole plant dies.



Thrips shred the leaf before sucking the chlorophyll, leaving damaged leaves increasingly white. They particularly like fresh growing tips at the top of plants.

White Fly


Larger in size – 2 mm – and resembling tiny moths, you’ll see these fly around if you shake the plant. They suck the sap from the underneath the leaf leaving white spots.

These are the most common pests likely to attack marijuana, but you may also suffer from leaf-cutters, caterpillars, slugs and snails and so on if growing outside. Good advice is to avoid infestations: keep your grow room clean and examine any plants that you bring in to it. And whilst this is impossible to do for the great outdoors, remember that the best deterrent to insect attack is a healthy plant and careful observation for the first signs of damage.

Solutions to cannabis pest problems:

Insects don’t just damage marijuana plants and the gardening world has many organic and non organic solutions.

▪ Insecticide soaps, prevent flying insects from flying to, and infecting, other plants.

▪ Neem oil – although this is better used as a preventative rather than a cure, it makes the leaf surface undesirable to insect infestations.

▪ Predators. Look online for predators that can be sent by post,Double check that your chosen predators will cope with the environmental settings of your grow room (especially temperature and humidity levels). Note it normally takes 5-6 weeks once you’ve received your carnivorous pests for them to clear an area.

▪ If you are growing outdoors, certain plants can be grown as deterrents or sacrificial plants. Know which insects are most common in your area and side plant accordingly.

PestPredatorCommon ingredient in pesticide
Spider MitePhytoseiulus persimilis, or “SpiderMite Destroyers” (a variety of ladybird – in the US, “ladybug”) + othersDycofol
White FlyLadybugs. Ichneumon fly (“assassinator wasp).Permethrin and Biffen
ThripsAmblyseius cucumerisPyrethin