Ask Ed: Grow Questions and Answers – Mite Infestation

CANNABIS CULTURE – Ganja Guru Ed Rosenthal on how to eliminate mite infestations.

Question: We have been growing for more than five years and we constantly have a problem with spider mites. Sometimes we use a homemade pesticide we make from dish soap, tobacco, alcohol and water. This knocks them out for one and a half to two months but then they return. How do they get into our garden? How can we protect the plants?

P.O., Ottawa, Ontario

Ed Rosenthal: There are a couple possible explanations for your recurrence of mites. One is that they have re-colonized your garden from outside and the other is that your knock-down spray, while highly effective, didn’t get every last mite. Just one fetid female can restart the cycle.

The mite road to your garden from outside has several arteries: they can hitchhike a ride on shoes, clothing, hair or garden tools. They can ride in on the air stream or thrill-slide through an unfiltered vent system to a veritable sea of green. They can also sail through an open window or door. The easiest is garden-to-garden transfer via plant or cutting. Nothing could be more convenient; they can continue to eat while traveling.

If your garden gets re-infested during the winter when there are no active mites outdoors, and you haven’t carried a mite in after visiting another garden, you should assume that you did not totally eradicate the mites or their eggs and the survivors repopulated the green room. Mite eggs are somewhat impervious to insecticides. If this is the case, the next time you spray, instead of a single treatment, use the pesticide three times, three to four days apart. That way any survivors or newborns will be killed.

Send your grow questions to Ed Rosenthal at [email protected].



  1. Anonymous on

    I usually do believe Ed. How late in the bloom cycle can you use Avid?

    Also, when can you put anything in the hydroponic water system?

  2. Anonymous on

    need help can you freeze mites out

  3. 420mikeykgb on

    mites try this it mite halp (magnesium sulfate) better know as epsom salt use like bag say for tomatoes all the way to harvest no more mites.

  4. Anonymous on

    mites like a dry enviornment, but other pests such as gnats thrive in a wet humid climate.

    the plant prefers relative humidity of 40% during flower and 60% during veg.

    if RH is too low during veg, you can get problems such as small leaf size and overall poor plant development. you want to cut the rh from 60% to 40% when the plant begins to flower.

    best way to control pests is to clean and treat the area with insecticide in between crops, if possible. also keep the area very clean at all times.

  5. earthman on

    If your having problems with mites , you should be misting your plants OFTEN with just water . Mites thrive in a dry environment . (such as indoor grow rooms) I am familiar with Avid . It works well , but I don’t think I would want to smoke it . Try safer soap for immediate infestations .

  6. Anonymous on

    Avid really works…..after you spray the avid imbeds into the growth of the plant….any mites infesting that eat will not reproduce as they have no way out of the egg.

    Mites are everwhere….even in the atmosphere waiting to come to earth.

    After avid introduction increase fresh air cut down on humidity. And don’t believe Ed.

  7. Anonymous on


    Follow instructions.

    Avid….will work follow instructions.