marihuana pests whitefly cannabis grow

Common pests in marijuana crops: whitefly

  • Whitefly (Trialeurodes vaporariorum) from the Aleyrodidae family is one of the most common pests in marijuana crops, and although it’s not the most lethal, you shouldn’t underestimate its capacity to ruin or at least substantially damage your crop.
  • These small winged insects approximately 1 mm in length look like little white moths and feed by sucking the plant’s sap. That’s why you have to watch out for this pest and eliminate it as soon as possible.
marihuana pests whitefly cannabis grow

How to identify whitefly

Whitefly initially install themselves on the tip of the weakest plant, and just like aphids, they feed on its sap as they spread downwards and conquer other plants around it. This leads to a reduction of chlorophyll and of the cannabis plant's vigour.

As the infestation spreads, the metabolic functions of the plants are slowed down, production drops and the deterioration of the crop's appearance becomes evident, looking increasingly weak and sickly. In addition, this pest acts as a vector for several viruses and bacteria that attack the crop worsening the situation, so you have to pay close attention because these are the signs that will indicate the presence of this troublesome insect:

Flies that flutter away when you shake the plant: the most obvious and unequivocal sign is when you see the insect flying from under the leaves when you shake the branches.

• Chlorosis: leaves that turn yellow, gradually dry out and end up dying.

• The presence of the honeydew that these insects secrete and which can cause the proliferation of fungi such as sooty mold.

• Appearance of yellow or translucent dots on the leaves.

• Appearance of a white powder on the underside of the leaves.

How to prevent whitefly

  • Observe: regularly inspect your plants in search of the symptoms described above.
  • If you're growing marijuana outdoors practise what is called "companion planting", which means planting close to the cannabis plants other pants that repel whitefly: calendulas, Mexican marigolds or basil.
  • Fumigate your plants with a horsetail solution as a preventive measure.
  • Use biological insecticides such as Neem oil or insecticidal soap.

How to eliminate a whitefly infestation

If your crop is already infested with whitefly you must act quickly to prevent them from spreading. Whitefly is hard to get rid of because it escapes by flying away, it's highly capable of moving to other areas and in addition it lays 190 to 200 eggs in each clutch. Therefore, if you don't act quickly, this pest can easily get out of control. There are different remedies that can help you to combat this insect:

  • Encarsia formosa wasp: this parasite is the most effective to eliminate this pest, and is harmless to humans. You have to introduce two or more individuals per plant and repeat every 2 or 4 weeks.
  • Macrolophus caliginosus: this voracious predator is not only used to control whitefly, but also to get rid ofred spider mites. It is an insect similar to a bedbug and attacks whitefly in all of its stages, eating both larvae and adults.
  • Use traps: this type of insect is attracted to the colour yellow; there are yellow strips of plastic covered in glue on both sides which, when placed strategically among your plants, will cause the winged adults to stick to it. Place them at a prudent distance from the plant, otherwise a gust of wind or a fan could cause the leaves of your cannabis plant to stick to it.
  • Spray with biological insecticides: spraying Neem oil, pellitory or insecticidal soap and Wormwood or Tansy infusions are effective for eliminating whitefly. Apply them insistently at intervals of 5 or 6 days until the infestation disappears.


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