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Marijuana Pests and Diseases

You are not the only one to love your weed. There are almost 100 organisms that also feed off of marijuana. We shall only cover the most common marijuana pests and diseases here.


Before we get into the wide variety of problems that you might encounter and how to deal with them your best option is stop pests and diseases from even getting into your marijuana grow room in the first place. You might consider using an insecticide before each cycle - even if insects are not apparent. Spray all corners, cracks and wall seams. Use a bug bomb or fogger for larger grow rooms if your situation allows it.

Soil-borne pests

One of the great advantages of using hydroponic/aeroponic systems for growing marijuana is that they prevent many types of insect and other infestations. There is no place for larvae to incubate and hatch. If you choose soil, it is a good idea to sterilize it, compost it or buy pre-sterilized soil.  Covering your soil with a layer of diatomaceous earth prevents flying and crawling insects from laying eggs as the sharp edges damages their bodies by abrasion. A less effective alternative is to cover with a 1/2” or so of fine perlite. The eggs will not grow in perlite and most insects will not burrow down to the soil.


Before you get started, make sure your grow room is impeccably clean.  Don’t give any potential pests or diseases a place to hide/nest/grow. Wash all walls, floors and surfaces down with soap and diluted chlorine bleach or other disinfectant. Depending on the surface, you may want to cover your floor with 6 mil thick plastic sheeting available at most home improvement stores. Do the same with all pots, buckets, utensils and other equipment. Repeat for each new grow. When changing out reservoirs, be sure to wash and disinfect as well. Do not bring anything in from outside – including work boots.

Environmental control

Keeping your air and reservoir temperatures and room humidity at the proper levels and using adequate air circulation will prevent many types of pests/infections from getting a foot-hold in your marijuana grow room. Filtering the air intake will block that path for many marijuana pests to enter.  The least effective method is to use a fine screen. This will keep out some insects and large particulate matter. Household air filters are the next step up and will keep out most insects and dust and hair. The best and most effective method is to use a HEPA filter. This will keep out all fungus and molds. However, as the pore size is so small, it will require quite a powerful intake fan to pull the air in as airflow may be restricted by as much as 70-80% over a free-flowing intake. Marijuana Pests and Diseases

Keep your marijuana plants healthy

A sick, injured or malnourished plant is more susceptible to disease. Even after taking all precautions, your marijuana might still become infected.

Fungus and molds

Bud rot and powdery mildew are the most common types of marijuana  infection. You must remove the infected parts and treat immediately before your whole marijuana crop is ruined. Lowering the humidity will help control the spread. A fungicide may be necessary. Marijuana Pests and Diseases Bud rot Pythium or root rot is another common enemy and is seen as discolored and/or slimy roots. Prune damaged or severely infected marijuana roots. It can be treated using diluted hydrogen peroxide. Using only filtered water and regularly sanitizing your entire hydroponic system will give you the best protection. Keep your reservoir temperature cool. Marijuana Pests and Diseases Damping-off is a fungus that generally attacks seedlings. The simplest prevention is to keep the soil dry between watering.

Insects and bugs

Spider mites, aphids, fungus gnats, whiteflies, thrips and lice, are among the menagerie of critters that may try to attack your marijuana plants. Sticky traps placed around your grow room are a good way to control flying insects and can also be an early detector of a possible infestation. Regular inspection of your plants is your best weapon. Check under the leaves as well as the tops. Spots or discoloration of your leaves may indicate feeding insects. Marijuana Pests and Diseases


Spraying your leaves with neem oil will help with many types of insects, mites and fungus. Some marijuana growers use it as a preventative as well as a cure. Home remedies include using diluted dishwashing soap or diluted garlic and onion juice as a foilar spray. Diluted SM90, a commercial wetting agent, is a good way to control whiteflies. Fine webbing is indicative of spider mites. Water with 10% bleach sprayed on leaves will help to control them. Marijuana Pests and Diseases Whiteflies

Tobacco mosaic virus

This is identified by mottled light and dark green patches on your leaves. There is no treatment for this – only prevention. It will not kill your plants, but will diminish your marijuana harvest. Hopefully this guide will help you control the myriad of marijuana pests and diseases that patrol your grow room. Prevention tactics should commence before your seeds germinate and careful monitoring of you plants should follow to hit marijuana pest and diseases early and hard if spotted. Find out more about controlling pests without the use of chemicals.