Dual Purpose Controls For Pests And Disease

Cinnamon Oil and Tea

Cinnamon, as a ‘hot’ spice deters many fungal diseases and insects alike. Powdery mildew, ants, aphids, fungus gnats, spider mites, thrips and whiteflies are among the critters that don’t like cinnamon. When used as an oil spray, the spice will adhere to leaves giving it time to work against many ailments.

As a control at ground level, sprinkle ground cinnamon around the cannabis plants or combine with diatomaceous earth in equal parts. This will be effective against ants.

To control disease or insects that are attacking your plants, employ a spray. Sprays can be availed commercially, or make your own from ingredients you probably have in the pantry:

  • Mix one teaspoon food grade cinnamon oil (available at health food stores and herb shops) with one quart water. Spray on your plants. Or…
  • Add two teaspoons cinnamon oil to one pint water and a couple drops pure castile oil.
  • To make cinnamon tea, boil one and one half pints water. Turn off heat and add one tablespoon ground cinnamon. Bring to room temperature. Add one pint rubbing alcohol. Strain, add to spray bottle and go to town on your plants.

Clove Oil

Clove oil is a natural repellent due to its scent and the resultant effect on certain pests coming in contact. Pythium, gray mold, Fusarium, ants, caterpillars, thrips, aphids and spider mites are repulsed by the scent of cloves. Although cloves flavor pumpkin pie and can be added to ham, it kills certain pests on contact. Hmmm, odd isn’t it? Nevertheless, it is an effective treatment. It becomes even more potent when combined with peppermint extract or citrus oil. Add a couple drops to water, as explained in the preceding cinnamon oil recipes, and spray. As always, do not spray during the heat of the day; early morning or early evening application will reap the optimum benefit.

Coriander Oil

Essential oils are the green means of dealing with pests in the cannabis garden. Essential oils can also be utilized in the home as an organic pest control and even as cleansers enabling you to discard harsh and harmful chemicals from your life.

Coriander resists Pythium, gray mold, Fusarium, powdery mildew, aphids, thrips, spider mites and whiteflies. Buy commercial treatments or follow the basic recipe for making oil sprays as mentioned throughout this article. Have you been paying attention?


Garlic has beneficial uses in our bodies and in the garden. Perhaps garlic is legendary to fighting vampires due to its repellent nature. Garlic, when ingestion by human beings guards against many maladies and aids in building a strong immune system. The same applies to plant life. Garlic has anti-fungal and anti-bacterial properties.

Use the basic recipe for making oil sprays, as mentioned in the oils section, and apply to new growth in order to ward off the emergence of attack. Be wary in the use of garlic spray as it can kill beneficial insects as well as those you need to eradicate. Garlic also offers an organic option for keeping deer from entering Mary Jane’s domain.

Download my free grow bible to learn more about pest control for cannabis plants.

Grapefruit Seed Extract

Grapefruit seed, sold as a concentrate in disinfectants, can control algae in the hydroponic marijuana grow room. Follow label directions.

Horticultural Oil

Most oil controls under this spectrum consist of mineral oils. Horticultural oils are meant to be applied prior to the opening of buds as a means of controlling aphids, fungus gnats, leaf miners, mealy bugs, scale, spider mites, thrips and whiteflies. Some oils such as jojoba, sesame and cottonseed oil also contain fungicidal properties, effective against powdery mildew.

Oil sprays fall into two categories: winter oil (applied during the dormant season) and summer oil (applied during the growing season). Summer oils should be used on marijuana plants. Do not spray during daylight hours, as you can damage your plants. No matter what you spray on your cannabis, do so in the early morning or early evening in order for it to do its job. Apply the spray directly to the pests, as the oil will dissipate on the outer areas. This is actually good news, making horticultural oils safe for humans and animals. However, always check the labels and follow directions.


Limonene is made by extracting the oils from citrus rinds. It can be applied as a foliar spray, soil soak and is even used as a household cleaner. When used in the garden, limonene dehydrates and asphyxiates ants, aphids, fungus gnats, mealy bugs, scale, spider mites and white flies. It will also control powdery mildew.

Mix two ounces limonene per one gallon water. Spray on leaves to kill plant dwellers or pour onto the soil for critters which do their damage at ground level. As always, apply early morning or after the sun goes down. Limonene is available commercially under several brand names.

Neem Oil

Neem oil is extracted from the nut of the neem tree, native to India. The insecticidal component of neem oil is azadirachtin which when applied, stops insects from feeding and developing. Neem oil is an effective defense against ants, aphids, fungus gnats, leaf miners, mealy bugs, scale, thrips, white flies and root weevils. Other components in neem oil have fungicidal properties combating gray mold, root rot, Septoria and powdery mildew.

The beauty of using neem oil in the cannabis garden is its low toxicity factor for humans, animals and the beneficial bugs you want to keep around. Neem oil is so safe for humans it is an ingredient in many household items such as toothpaste, shampoo and cosmetics. It is considered an organic control, will not harm the environment and can be found at local lawn and garden centers.

Neem oil can be applied as a foliar spray, soil drench and is safe to use in hydroponic systems. In the latter, apply one teaspoon per quart of water. The oil will be taken up by the root system and distributed throughout, protecting the plant from attack.

As a foliar spray, test an inconspicuous area of the marijuana plant before applying to the entire plant. Wait twenty four hours to see if it is well tolerated. Once confirmed, spray the leaves lightly. This should be done weekly until there is no longer evidence of pests or disease. Do not apply in extreme temperatures or during the day. Apply at night to allow the leaves to absorb the oil.

Sesame Oil

Sesame oil contains both insecticidal and anti-fungal properties. Spray on Mary Jane to rid her of aphids, fungus gnats, leaf miners, mealy bugs, scales, spider mites, thrips, white flies, gray mold, Septoria and powdery mildew. When purchased commercially, treatments will typically contain other oils such as clove, thyme, soybean and wintergreen.

To make a sesame oil spray at home, add one teaspoon sesame oil (available at health food stores) to one pint water and a couple drops pure castile soap. Spray on plants either before sunrise or after sundown.

Wetting Agents

These are necessary to oil applications, allowing adhesion of the spray. Without adding a wetting agent the oils will simply slide off the leaves before they can have a positive effect in controlling fungus or pests. The most recommended wetting agent is pure castile soap. Do not use liquid dish detergent because they can be too harsh, rendering the oil sprays ineffective.

Avatar for Robert Bergman

Robert Bergman


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

50 comments on “Dual Purpose Controls For Pests And Disease”

  1. this article was very helpful. I have 2 small plants that have catapillar damag and ai have colleted 2 of them and sent to out doors….thanks for this info.

    • Hi Roberta,

      We’re happy to hear you’ve found this article helpful!

      Happy growing and let us know if there’s anything we can do for you,

  2. Lost 90% of my harvest in the last three weeks of growth to caterpillars. I sprayed w/ Neem oil once a week till flowering. didn’t work. what can I do to prevent this from occurring next time ?

    • Phil S.

      Caterpillars are a tough one to eradicate. You have to be diligent and pick them off everyday. Insecticidal soap, and homemade pepper sprays work OK. You can look into companion plants that attract the pest, plant them and maybe the caterpillars will eat your companion plants instead. Also; You can dust around your plants with Food Grade diatomaceous Earth, which scratches them and causes them to dehydrate and die.

      Good Luck. Join our forum and ask around. We have many friendly outdoor growers who might have some more answers for you. 🙂

      Happy growing 🙂

  3. Got something for the smokers world . Cheyenne pepper, onion. Garlic, bring to a boil , once boil strain through a coffee filter make sure you use enough water to make a gallon , after it cools add soap.

  4. I am 5-7 days away from harvest on balcony. I have been picking off mealy bugs with tweezers 2 to 3 in the past 2 days. Any particular oil works better for these?

  5. Just about to start my 12/12 switch insects and mould is my worst fear. As im in the uk I’ve got different bugs but will try those recipes of knowledge. Just having some rare Sunshine here so plants in garden from early day time then back under lights. Had the odd ant but small price to pay for Sunshine on my girls. Thanks to all for the advice. Mr toad uk

  6. Robert, thank you for the growing and processing tips. I can’t wait for spring to plant your super seeds. I used bag seeds this and year and had fair results.

  7. Jenny M. Leonard,

    Depending on which essential oil you are referring to. When applying oils to plants, in flower cycle; We do not want to spray the buds late in flower. Application can be made on the leaves, just like foliar feeding.

    If I ever have to use an oil or soap, DE, etc… I place the whole plant in a tepid shower follower by drying in front of many fans to prevent mold, etc…

    Hope this helps. Join our forum and we can get more in depth. Peace

  8. About the essential oils. Can you use them at the end of the flowering stage? Also, will they effect the flavor of the weed.? Seems like you would be smoking a cinnamon/clove/etc., tasting bud. I know essential oils have many health benefits- however I have not read or heard anything about smoking them. Thank you for the help.

  9. Question regarding this quote from blog article… “Horticultural oils are meant to be applied prior to the opening of buds”

    Is this to mean don’t use these techniques in vegatative stage?
    But only use during flowering stage?

    • Brock,

      I think it means; “We do not want horticultural; soil which contains all the fertilizer needed for the start of a grow. Once buds open we do not want all the Nitrogen that is in the H soil in the beginning.

  10. Companion planting is very useful to deter pests. Garlic and chives will repel spider mites. Everyone’s worst enemy will not come near your plants if you have a pot of chives nearby, or planted in the soil next to them if growing outdoors. Thanks for the tips ILGM, and the best seeds I have come across. High germination (100% so far), great stock with very strong and healthy plants, fantastic varieties. Thanks Robert and the team

  11. Had a major problem with caterpillars this year and lost 95% of my harvest to them. I’m growing outside and wondering what to do next year to help with this issue. Total bummer…

    • grow nasturtiums as a companion plant. Butterflies will lay their eggs on them in preference to your flowers. Easy to grow, they also self seed readily and provide some lovely colour. Also you can eat the leaves and the flowers in salads and if you bottle the seeds in brine they are just like capers.

  12. Chickenhole,
    I see no reason to apply that to seedlings. This is a home made pest remedy that should be used in case of a pest problem. If you are indoors and keep[ your grow environment clean, you probably do not need to apply this to sprouts/seedlings.

    Outdoors, perhaps this could be used proactively with “Food grade DE”, around the base of plant but, I would not advise spraying something on small plants unless it is needed.

    If you need more help; Feel free to join our support forum.

    Happy growing 🙂 lw.ILGM

  13. I would use a commercial companies products. In a lot of cases; Home remedies are used more in an emergency situation. So Buy Robert’s products.

  14. Have posted this question on forum but how do these (home remedies) compare to using the Bergman protection system (root, bug, mold preventer)?

  15. Having a new problem this year with root aphids, which some say are impossible to get rid of. I’d like to use essential oils and stay as natural as possible, if you have any suggestions, many thanks!

  16. One full teaspoon of fine ground Cinnamon (Asian is the best) boiled in a 1 quart of water, was perfect for ALL my insect control.A mixture of 1/2 teaspoon Thyme oil, 1/16th teaspoon Cod liver oil, a few drops food grade Glycerine, 1/16th teaspoon Lauric acid (or citric acid) in 1 gallon carbon filtered or distilled water (Ph Neutral) poured into a spray bottle kills all fungus, but use sparingly. Totally non toxic and leaves no residue or taste in the final harvest. Can be used up to 1 day before harvest day! A quick rinse with clean water right before harvesting is always a good idea. Just room dust and other airborne particles should be rinsed anyway. Happy growing!

  17. Ilove growing,

    You can buy some Food Grade CODEX diatomaceous Earth. I would post you a link, but the blog won’t let me.

    If you fo to our Support Forum and look in the Buyers Guide section You will see a link I have posted for this product “DE” at amazon.com
    Painting the room will eradicate any future eggs from hatching.

    If you have any more issues; Join the forum, and find several good folks ready to help you out. Peace

  18. Hi All,
    First I want to say Thanks to Robert, Claire and all at ILGM for the great service and even better seeds !!
    Was wondering if anyone had any idea how long I would need to keep a room vacant to make sure any spider mites that might be in the room die off as well as any eggs? Is there something I can clean paint and flooring with that would do the same as time?

    • My suggestion is to wash everything down with a weak bleach solution. Also use a spray bottle to get into any gaps and spaces where you cant wipe. Standard bleach diluted as per the bottle for wiping surfaces should kill everything. Bleach degrades quickly in the environment and leaves no residue.

  19. A friend that has been growing cannibas for nearly 40 years told me to slice potatoes and lay on top of the soil of your plants to rid fungus gnats. The potato slices will draw the fungus gnat larvae up out of the soil from around the plant roots and eventually die. I hadn’t tried this yet so can’t say it works or not. I know one thing, I’ll be trying out some of your recipes as I’ve had trouble with fungus gnats with each grow. I’ve tried commercial products such as granulars that you sprinkle onto your soil before watering but the fungus gnats never went away. I even let the top soil dry out for 2-3 days…the fungus gnats came back! Essential oils here I come!

  20. Nancy,
    I have heard of people using Cinnamon spray but, i I don’t. Best thing is a TBS of Baking Soda in a Squirt bottle. This is very alkaline, and Mold cannot thrive in an alkaline environment..Do it sparingly, and plan to give your plants a shower before harvest. 🙂

  21. I’ve got plants in bud, 3 that are almost ready to harvest, but they have developed powdery mildew. At this stage, I have started removing the mildewed leaves, but I’m wondering if it would be alright to apply a cinnamon spray to them? I’ve got 2 other plants that won’t be ready for several weeks. One is just starting to show some mildew. Again, is it safe to spray this late in the bud stage? At the rate the mold is spreading on the one plant in particular, it will be an early harvest.

    • With powdery mildew I mix 8oz of hydrogen peroxide with 2-3 gallons of water in a large but shallow bin. I soak the buds for approx 5 minutes and you’ll see the PM scum raise to the surface. I then lightly hose the buds off with water and shake lightly. I then hang them in the drying room. Thank goodness it works!!!

  22. I will be moving to Arizona with a friend of mine will be able to flower 22 plants at 1 time with 2 mothers I was thinking of using stealth hydro bubbleponics 5 gallon buckets but seems a lot of maintance with 22 bucket and hoses second thought use ebb n grow hydro growing horz what do u think best way to get most dry weight in 1 year I am disabled so I will be with them 24/7