Top tips for preventing pests outdoors

A ladybug eating plant villages on a plant

The outdoor gardener is at the mercy of the elements and whatever nasty surprises Mother Nature may like to throw at us, such as moulds, diseases, and of course, insect and animal pests. Here, we focus on some minimal-impact, environmentally-friendly ways to control pests outdoors, so you can avoid use of heavy chemicals.

Make sure your soil is sterile

A huge number of pathogens may be found lurking in soil. Usually, if you buy your soil or soilless mix from a reputable supplier, it should be free from the parasites, microbes and tiny insect pests that can be found in regular outdoor soil.

However, if your local soil is of particularly high quality, you may wish to utilize it rather than incur the expense of buying it in. In this case, you may wish to consider solarization or steam sterilization, which kills off the majority of harmful soil residents while allowing several important heat-resistant and beneficial bacteria for your cannabis plant to survive.

Grow companion plants

A purple geranium flower
Highly-fragrant geraniums are often used as companion plants to ward off insects (© Jacilluch)

Companion plants are an absolute godsend for the outdoor gardener; gardeners and farmers all over the world have been using their native “helpful herbs” for centuries, if not millennia. A well-known example is the South American method of planting maize, beans and squash.

For cannabis, known companion plants that repel insects and small animals include geranium, marigold, garlic and onion. Garlic in particular is highly rated as a companion as it can repel aphids, spider mites, and even mice and rabbits. Intersperse your companion plants between your cannabis plants, or if possible plant a “boundary fence” around your entire cannabis crop!

Use beneficial insects

Beneficial insects are another ace up the sleeve of the organically-minded outdoor grower. Ladybirds or ladybugs (general terms for small beetles from the Coccinellidae family) are particularly well-known for preying on aphids, and many growers also swear by them as a means of controlling spider mites.

Not everyone finds that ladybirds alone are a match for the invasive and devastating spider mite, and if your problem is severe it may be wise to consider introducing the predatory mite genus Phytoseiulus, available in most good organic farming supply outlets.

Animal urine is a great repellent!

For small animal pests such as rabbits and mice, and even larger ones like deer, using the urine of species that habitually prey on the pest species is an excellent idea. For rabbits, the urine of the red fox is ideal; for mice, stoat or mink urine may work. In the U.S., prey species are hunted by a whole different set of predators, and puma, bobcat and bear urine can be invaluable for repelling a whole range of pests including deer.

In parts of the world that have eradicated large predator species, such as the UK and the Netherlands, using unwashed human hair or lion dung is said to be an excellent alternative. Before you start wondering how on earth you are supposed to procure stoat urine or lion dung, there are various specialized retailers online that can provide what you need, either from “real” sources or synthetic.

Fencing and wire cages

Building fences and cages around your plants is one obvious way to repel larger pests, though it is likely to do little to prevent insects getting to your crop. If conducting guerrilla grows out in the wilderness, this may be somewhat less of an option, as large structures such as fences may be a visual indication to nosy passers-by (or law enforcement!) that something is going on.

However, wire cages can be practically invisible from a short distanced away, particularly if the wire is painted green to help disguise it. As long as your fences and cages are well-constructed, they should be all you need to keep out deer.

Rabbits can be harder to repel in this manner, and if they are a problem, sinking the fences at least 15cm (6”) into the ground and forming them into an L-shape (as described in this guide) is about the only way to go. Even that may not be 100% effective, as rabbit are tenacious creatures that love to dig!

Use natural pesticides where possible

If the above methods do not provide total protection from pests, the next step is to look into repellent compounds that can be sprayed onto plants to render them poisonous or unpleasant to pests.

There are hundreds of commercially-available synthetic products, but many of these can be hugely detrimental to the health of the local ecosystem and your cannabis plant. To avoid causing damage to the environment, organic farmers use pesticides derived from natural plant sources, such as neem oil, citrus oil, cayenne pepper, and garlic oil.

These natural pesticides have been used for millennia by farmers throughout the world, and in historic times were the farmers’ main defense against insects and animals. You may find that a combination of different organic pesticides gives you the protection that you need; a good source of recipes for specific pests can be found here.

Create a ‘magic circle’ around your cannabis plants

Stacked cayenne peppers on a plant
Cayenne peppers contain natural compounds that can act as a repellent to insect and animal pests (© JKD Atlanta)

If the thought of coating your precious plants in noxious sprays is anathema to you, it may be possible to use organic pesticides to protect your plants in a slightly different manner. Instead of spraying your pesticide mix directly onto the plant, try spraying it in a wide circle around your plants, leaving a gap of at least one metre (3.28’) between your cannabis plants and the ring of pesticide.

This ‘magic circle’ should cause insects coming in contact with it to die, or at least beat a hasty retreat! Of course, it may be advisable to respray the circle every week or so, to ensure that the strength of the magic circle is not compromised.

This method has the added advantage of being usable throughout the grow cycle, whereas if you spray directly onto your plants, you will have to cease doing so by the time they are in full flower—if you don’t, you risk your final product tasting odd or even being unusable.

  • Disclaimer:
    Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.


3 thoughts on “Top tips for preventing pests outdoors”

  1. Rabbits and deer, which are vegetarians, are repelled by the smell of blood meal and really any kind of animal parts like chicken bones. Sprinkle liberally around the garden and they won’t go near.

  2. Action Property Inspections

    Great article thank you. I am about to embark on a new journey of growing a garden with the kids and this will be really helpful as I had no idea about companion plants with pests

  3. In our area along with spider mites we’ve discovered the dreaded Cannabis Russet Mite – a maggot-looking almost microscopic terror that decimates every plant it gets a foothold on. None of the standard spider mite remedies even touch these little monsters, and sulphur (reported as effective against russet mites but not spider mites) will burn plants when used with the normal neem/azatrol spray for spider mites.

    Last year I stumbled on a new product made in California called Green Cleaner that is 100% effective against russet and spider mites both. I have no financial or other interest in this product – I’m posting this because in over 10 years I’ve never had completely pest-free plants until I started using Green Cleaner.

    It’s a combination of oils, sodium lauryl sulphate and alcohol along with other stuff – none of which even registers with the EPA as being toxic at the concentrations involved. It seems to kill the eggs as well – I spray once a week or two (this stuff smell just like shampoo) and there is not one spider mite bite nor russet mite larvae visible anywhere.

    I wish I had invented it or owned stock or something, but I’m just an enthusiastic consumer happy to buy it at retail. It’s truly the magic bullet in plant health around here in N. California.

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    Sensi Seeds

    The Sensi Seeds Editorial team has been built throughout our more than 30 years of existence. Our writers and editors include botanists, medical and legal experts as well as renown activists the world over including Lester Grinspoon, Micha Knodt, Robert Connell Clarke, Maurice Veldman, Sebastian Maríncolo, James Burton and Seshata.
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