Pests Affecting Indoor Marijuana Plants

MoldIn the process of mastering how to grow marijuana indoors, know not only the techniques of growing for greater yield but also familiarize yourself with common marijuana diseases and pests that you might encounter. Prevention is the best line of defense against these pests. Maintain a clean growing environment, maintain the standard level of temperature and humidity and provide good ventilation. All these will help prevent future problems that you might encounter as you cultivate weed indoors.

Fungus Gnats

power-plant-medical-marijuanaThese are bugs with gray or black bodies and have clear wings. They can affect marijuana plants that are grown in a dark grow area with damp condition. These pests can attack cannabis seedlings and roots of bigger plants, causing them to weaken.


Marijuana plants infested with fungus gnats may look weak. Check on the surface of the soil medium or around the roots of the plants because these pests love to feed themselves with dead leaves. As you move the plants or water them, fungus gnats become active, so keep an eye on them.


If weed plants are stricken with fungus gnats, use an insecticidal soap or spray a neem oil. You can also use Bacillus Thuringiensis which is found in products such as Bactimos or Gnatrol. These pests love to thrive in moist conditions, so keep the humidity level down and the soil not damp.

Spider Mites

SpiderMitesCloseSpider mites are not easily recognized because of their very small size that they almost look like dots. These pests are commonly affecting cannabis plants cultivated indoors. They are arachnids and belong to the same family as the spiders. They can multiply quickly and are very hard to eradicate. Marijuana plants attacked by these pests will slowly die if left untreated.


The appearance of tiny brown spots circled with tiny yellowish areas is one of the indications that your plants are infested with spider mites. Look at the underside of the leaves because these pests usually thrive in this area. To detect tiny spider webs and the presence of spider mites, gently spray the area with water.


Neem oil, which is derived from Neem tree, is an effective mite repellent. Aside from spraying neem oil, you can also use a natural pesticide like pyrethrum. Another way of eliminating spider mites is by introducing lady bugs to the indoor garden.

White Flies

whiteThese are small insects that look like moths. Marijuana plants’ growth may be stunted if they’re stricken with white flies because these pests will slowly draw out the life of the plants as the chlorophyll slowly diminishes.


Marijuana plants attacked by white flies will have the appearance of white or yellowish spots on top of the leaves. To identify them, gently shake the plants.


Introduction of predators like Encarisa Formosa (tiny wasp) is one of the ways of eliminating white flies in an indoor garden. Spraying water mixed with vegetable oil or garlic oil concoction is a natural method of killing these pests. Another is the application of pyrethrum every 5 to 10 days.

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