by Adrian White
20 December, 2021 by
Lucija Johum

It finally happened: you encountered the first pest to sneakily find its way into your greenhouse. If you’re a conventional grower, the solution to this is easy. Most likely you’ll be getting your next batch of pesticides ready to spray over your greenhouse plants, or you’re planning on making it an added part to your greenhouse routine.

But what if you are an organic grower with a greenhouse? If you chose this route of more sustainable, ecological plant care, you knew this day would come. It’s time for you to figure out how to keep the pesky pests at bay without all the sprays and chemicals.

Luckily, long before pesticides were ever created, natural methods of keeping away bugs and insects were plenty. Among the savviest organic farmers and gardeners, chemical-free tips and tricks are still being used today, and with great success. If you want the very best and most common among them to keep your greenhouse protected, explore some of our favorites below.


Especially if the gardening operation under your structure isn’t very large, removing pests and insects by hand is one of the simplest, most basic methods. Keep in mind though: the larger your grow system is, the more time it will take to remove them. Plus, it only works ideally with larger insects you can see, of course – very small pests in great amounts obviously won’t benefit from this approach, as it’ll be too difficult. 

This method may be used with potato grubs for example. These are large white worms that burrow around the roots of your potato plants, and that feed on or damage its roots and tubers.

Tomato hornworms are another example. Though they camouflage well with your plants, they can still be detected easily and removed by hand.


It’s easily said that pests enter your greenhouse because they were attracted there in the first place. For organic growers, the good news is that you can control some of these factors without too much trouble.

Things like debris, rotting plant matter, standing water, and plant diseases are big invitations to the pests you want to keep away. The logical advice here: keep things clean! This doesn’t just mean cleaning the greenhouse, but also keeping your plants clean and healthy – and this means cleaning and removing rotting or dead foliage regularly.

Make sure to avoid excessive moisture and water, too. This is the perfect breeding ground not only for many insect pests, but plant diseases, too. As such, keep your grow space clean, dry, and tidy!


When it comes to taking care of plants in any situation, you can never underestimate airflow. Not only will it help keep things dry (and plants healthy, for that matter) as described previously, it will also have a noticeable impact on the pest populations and conditions under your cover.

Putting it simply, pests and diseases are attracted to anaerobic conditions – that is, stifled and damp areas that aren’t exposed to enough oxygen or airflow. Making sure that airflow is healthy and balanced will help ensure that unwanted critters don’t get out of control. Damp, anaerobic conditions lead to disease, which affects plants, and then attracts bugs; to prevent this, you can achieve great airflow with a top-of-the-line greenhouse ventilation system. 

Of course, having your greenhouse ventilated by opening and closing it at certain times of day allows the pests you don’t want around to escape in the first place. You may achieve this with roll-up sides, or the more standard channel and wiggle wire greenhouse sides, in addition to keeping greenhouse doors open and closed.


Similar to ventilation, closing up your greenhouse at the end of the day is always a smart move. That is, whenever shutting down your greenhouse is possible, without raising temperature too much. This preventive measure can keep any undesirables out of your covered structure in the first place.

On hot days when ventilation is absolutely required – even throughout the nighttime – this isn’t always a possibility. All the same, for beginning greenhouse growers out there, shutting down your covered growing system is a good thing to get in the habit of – especially at the end of the day on nights when your plants can stand it. A good tip: avoid leaving your structure open just because you didn’t get around to it!


Some growers may not realize that pest prevention might happen simply in the way you grow things and the methods you use. Crop rotation is an excellent example of this. Farmers and gardeners who are particularly vigilant about soil health know that when you avoid planting the same plants in the same soils year after year, you see a considerable decrease in certain pests.

For example: planting potatoes in different places every year lowers the population of bugs and diseases that get attracted to them. The same goes for practically any other plant. If you switch where it’s grown every other year (or even every few years), the pests that are attracted to them won’t have enough time to establish and become a problem.

For that reason, don’t plant the same thing year after year in your greenhouse, and keep a rotation (or learn how to keep one). You can also cover crop between plantings, which helps enrich and nourish your soils so they stay healthy. If you don’t rotate, don’t be surprised if you see some very big pest populations over time!


Similar to crop rotations, companion planting can provide some natural barriers against insects pestering your crop year in and year out. In fact, companion planting is becoming quite popular in the world of agriculture in general. Many companion planting pairs are beginning to be very commonplace sights in gardens.

What does companion planting do? In short, some plants naturally repel certain pests with the oils they produce. Plant them alongside different plants that tend to have issues with those exact same plants, and a companion planting partnership is born.

Learn the best companion planting pairs, and give it a try in your own greenhouse. You may just see less pests around as a result.


One of the best ways to prevent pests? Work in harmony with nature so she does some of the work for you. The most interesting way you can do this: attract natural predators to your greenhouse that will munch away on those pests you hate.

You can do this is with some clever companion planting. Bring herbs, shrubs, or other plants close to your growing space that attract or provide nesting places for birds, spiders, wasps, and other critters – and particularly ones that will love to dine on your greenhouse pests. Otherwise, you can go so far as to obtain these predators themselves for release in or near your greenhouse – lady bugs and parasitic wasps are some good examples of beneficial predators you can purchase, even online.


What can you apply directly to (and around) your plants to have some pest control? You know you can’t rely on chemicals and pesticides if you grow organically. But are there natural equivalents?

Organic growers over the years have certainly picked up their own tricks. For example: putting cinnamon around some plants can help repel ants. Or, to keep slugs away or lower their impact, set up beer traps.

These small but effective methods can especially be helpful in smaller sized growing systems.


For direct protection of larger systems, investing in nettings or screens can be a real help. These come in the form of very large rolls of material that are unrolled and stretched over entire greenhouses, high tunnels, hoop houses, and more. Their function: keeping pests out of your growing space while keeping the beneficial ones inside it.

Some are designed solely for insect protection. But if you are also wanting to keep out birds, bats, rabbits, and larger critters out, you can invest in netting that helps with that, too.


Another method that works well for larger critters: fencing! Have issues with raccoons, deer, and rabbits getting at your greenhouse crops? Investing in adequate fencing can be a real help, though make sure you look into the right fencing for the right animal.

Deeper, dug-in fences will obviously work better to keep rabbits away. A much taller fence, on the other hand, will be needed to prevent deer from jumping over and getting at your plants. While housing plants in a greenhouse structure can create quite a bit of protection on its own, surrounding your systems with added fencing raises your guarantee that you won’t experience larger pest damage – especially on nights you keep your houses open.


When worst comes to worst, there are some man-made pesticides that fall under the organic certifier label. While they are still technically chemicals, they are naturally-derived, which makes them biodegradable – and ultimately they won’t be a harm to plants, humans, wildlife, or the environment. Look into these options if you decide this is the path you want to take. 

They can be excellent last-ditch options, especially if pest issues are getting particularly out of hand and while still keeping things organic. Some organic pesticides are derived from chemicals naturally produced by chrysanthemums, for example – flowers that have their own natural defenses to keep pests away. Others are made of completely biodegradable matter that, when consumed by certain pests, can kill them (though it won’t harm the surrounding environment).


Just because you’re going organic doesn’t mean you won’t have any available methods to keep those unwanted bugs and critters away. 

Keep the above methods and techniques in mind, and explore your options depending on the pest you’re dealing with. Many of these are just as successful, and you won’t have to sacrifice your organic standards to chemicals just to have strong, healthy greenhouse plants.

Lucija Johum 20 December, 2021
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