How To Keep Bugs Out Of Your Greenhouse: Top Tips That Work

Among the most harmful components to greenhouse vegetation is insect infestation. Although gardeners battle pests in their outdoor plants, those grown in a greenhouse are more at risk. Being in a controlled environment with no access for predators to feed on the insects, the pests can thrive further destroying the vegetation. An indoor garden means more work for a horticulturist who has to work harder to maintain it.

Can you keep bugs out of your greenhouse? It will mean extra effort on the part of the gardener, but you can keep bugs out of the greenhouse using multiple methods, one of which can include spraying the vegetation with insecticide. The substances have the purpose of eradicating, repelling or disabling a variety of pests. Unfortunately, some pests in the eradication process are actually good for the environment. 

For the home gardener or someone working in the gardening industry, research is a necessity, particularly when it comes to using sprays for eliminating colonies of bugs. A natural, organic approach for the plants and the environment is essential and useful in the eradication process regardless of the species. Bugs reproduce at alarming rates meaning a rapid recognition of the type of pest and remedy required is vital, followed by immediate treatment.

Natural Remedies For Keeping Bugs Out Of The Greenhouse

If you are a gardening hobbyist who operates inside a greenhouse, you will have the added responsibility of battling pests as natural predators are kept at bay. 

The optimum method of protecting the individual vegetation is to spray the plants with a natural insecticide. It creates a barrier between the bug and the garden. There are a variety of natural remedies on the market. Each works differently with its own efficacy. Despite these products’ organic elements, it’s vital to follow the guidelines provided for safety purposes.

  • Bacillus Thuringiensis (BT) – Beginning in 1920, BT has been a useful bacteria-based tool in controlling infestations of pests, whether inside greenhouses or outdoors. It is an all-natural product that produces crystalline/spore insecticide proteins. It brings no harm to anything of benefit to the environment, nor is it harmful to people or animals.
  • Spinosad – The nervous system of a bug is affected by this specific bacteria known, also as saccharopolyspora spinosa. This insecticide is advantageous for a vast array of species, but research is necessary to ascertain at what point of the lifecycle will be the best time for eradication. 
  • Neem oil – Insects suffocate through the use of neem oil, which will also repel bugs. Any indication of the oil on a plant will cause a bug to go the other way. Neem is responsible for the isolation of Azadirachtin, which is in many natural insecticides. It directly affects a bug’s molting ability and repels insects from reproducing. If you decide to go this route, be sure to get the pure stuff and not the “from concentrate” as it’s more effective.

Tips On Keeping Bugs From Entering The Greenhouse

Each time the greenhouse door opens, there is the opportunity for a bug to invite itself inside to either feed or perhaps pollinate a plant or two. 

They may fly, crawl, or ride in with you when you come in or go out. Once inside, the plants will need an insecticidal barrier for protection. But ideally, keeping as many from getting inside as possible is going to be the goal. Prevention is possible using various barriers, screens, traps for any gaps or openings to the greenhouse.

  • Know your source. Starting your plants from treated seeds that come from a reputable dealer whom you have a long-term relationship with will ensure that there are no fungal or bacterial issues for which the plant may have predisposal. Any time you purchase an already-established plant from a gardening center or nursery, there is no guarantee that it is healthy or infestation-free. Seeds that have pretreatment allow for safer vegetation to begin in your greenhouse.
  • Keep the outdoors out. The floor of the greenhouse should have a cover as prevention of bugs digging up through the soil from outdoors. If you have a garden both in the greenhouse and outside, you want to keep them completely separate. 
    • The plants outside should never find their way into the greenhouse as they can potentially bring bugs with them. And if you need to work in the outdoor garden, do so after your work is complete inside the greenhouse.
    • Oh, and keep the door closed at all times!
  • Use care when repotting. The process of repotting a plant needs to happen outside the greenhouse, and the recommendation is that you use a ‘soilless mix’ whenever starting seeds or planting for the greenhouse. Any soil mixture that you use for greenhouse vegetation has the potential to introduce a variety of insects or microbial pests that the soil harbors. Pots you choose to recycle should go through disinfection first using a 10 percent bleach cleanse.
  • Keep tools clean. A 10% bleach cleanse is suggested for all gardening tools before using them in the greenhouse in case there is any chance for bugs or bacteria coming with them from the outside. Ideally, they should go through the disinfection process when working on each plant.
  • Keep a sanitary greenhouse. Perform a routine weekly removal of any fungi or mold that may appear. At the change of seasons, deep disinfecting is necessary with the removal of everything from the space and complete wash-down. Ensure that there is never any standing water anywhere in the greenhouse, a natural attractant for bugs.
  • Examine your plants. Taking care of the plants in the greenhouse means inspecting them regularly to make sure that they have no bug eggs, larvae, or beginning of an infestation, bacteria, or fungi developing. If you see any issue, the plant should leave the greenhouse so it can’t endanger any of the other vegetation. It can be treated in another area and brought back in when the problem is under control. 
    • Go over all new plants to make sure they are free of contaminants before they enter the greenhouse. A simple oversight of one insect on a new product can lead to an infestation of the entire crop inside the greenhouse.
  • Keep a clutter-free space. Many pests are attracted sweet scents and enjoy hiding out under a load of clutter. When working inside the greenhouse, keep sugary drinks covered (if you must bring them in at all). Keep pots, tools and any other elements orderly and the inside space free of ‘stuff.’ On the outside, keep the grass mowed and bushes trimmed. 

The Top Enemies of The Greenhouse Garden

A greenhouse garden is different from that of the outside crop as its humid, warm, and insulated. There is a multitude of pests that can find their way in to feast on the vegetation. While some of these pests actually have good intentions, others can bring greenhouse disaster.

The ones that need to find their way out include fungus gnats, aphids, and whiteflies. These bullies are among the most prevalent and persistent in finding their way in and have no preference as to the time of year. Let’s look at each one individually.

  • The Aphid: a Greenhouse’s Number One Pest
    • Its oval shape and golden color are distinguishing features of this insect. The aphid notoriously holds the number one position of top pest.  They typically hang out in clusters underneath the plant’s leaves. The wild thing about the female is her capability of reproducing without the need to mate. She does so at a very rapid pace (within a week), with only females being born.
    • Aphids are a problem that you need to find immediately as they will take over the greenhouse
    • Inspect the plants routinely, paying close attention to the surrounding environment regularly.
    • Make sure to have someone who can do these things if you need to be away for an extended period. Leaving the greenhouse unattended for any duration could result in destruction if aphids take hold. 
    • If you do find aphids early enough, the eradication process is not very difficult as aphids can simply be washed away with water either through the use of a spray bottle or a hose. Each leaf of the plant needs turning over and gentle washing, which will disturb the aphids to the point that they won’t want to return. The vegetation is fragile, so care needs to be taken. 
    • The aphids may overindulge on some leaves, causing loss of the blade without too much harm coming to the overall life of the plant. You will need to engage in the eradication process every other day until the aphids decrease in population. 
    • These little guys can be determined particularly throughout the cold months with certain species developing wings. They are known to move to other areas of the space, so be sure to inspect all parts of the greenhouse regularly. 
  • The Fungus Gnat 
    • This bug likes soil, particularly the very top layer, where they will lay their eggs. It is the next most significant problem suffered by the greenhouse garden. When this gnat hatches, it is comparable in appearance to a fruit fly and has become a typical annoyance to those tending to houseplants. They enjoy decaying plant tissue along with seedling or leaves.
    • To protect vegetation from the fungus gnat:
      • Cover the soil since this is their habitat. You can do this with things like stones or crushed granite (poultry grit) disallowing their ability to hatch. 
      • Use watering systems that keep the topsoil dry. 
      • Once the gnats develop wings, you can use yellow sticky tape to attract them. 
      • They have a habit of congregating in windows or lying in the sills, so you can kill them there with a cleaning solvent.
  • The Whitefly
    • There are numerous pests that come into the greenhouse. At this point, there is a number that could hold the number three position. But it’s a matter of which are typically seen year-round more commonly, and it seems that would be the whitefly. These can be comparable to gnats for which the eradication process is inclusive of the use of sticky traps.
  • Thrips
    • These are tiny, slender insects that quietly do their damage within buds or the tips of shoots, sucking out the life of the plant. Often, you will see the damage before you even know this insect is there. If that is the case, you must prune all damaged flowers or buds and wash the remaining areas with insecticidal soap or neem oil. Since some thrips can fly, sticky tape may be helpful here.

It’s impossible to keep a completely sterile, bug-free environment for the greenhouse. Ideally, you want to offer your plants a place close to their typical ecosystem that is balanced and healthy, where they know the way to defend and ultimately recover from an attack.

Make Friends With These Bugs in The Greenhouse

Many bugs are a benefit for the garden. These you want to invite into the greenhouse to help out with the pest problem. If you kill beneficial bugs, your effort in the greenhouse doubles.

It is important that you become versed as to which insects are a benefit because they can play a vital part in assisting with the health of your garden. 

As a gardener or horticulturist, it’s essential to research not only vegetation but the environment as a whole, including the purpose and function of the different bugs so that you can use them to your advantage. 

Those bugs that are an enemy to your garden can often be eradicated in a natural way via their predators. Unfortunately, using even natural insecticides will eliminate the bad bugs but can take away the good ones as well. Knowledge is key to a healthy, well-established ecosystem. Here are a few of the bugs that you want on your team:

  • Green Lacewing. Among the most popular and well-known of the useful insects is the green lacewing because the aphid is its food of choice.  Thrips are also on this insect’s menu. It can indulge in many of these destructive pests, as it has a healthy appetite.
  • Praying Mantis. Sure, it may look a little scary, but it loves to eat aphids, thrips, caterpillars, flies, crickets, moths, you name it. It is a substantial bug that can kill any other pest, with some large species having the ability to prey on tiny birds.
  • Ground Beetle. This ugly-looking bug could easily be mistaken for a bad bug, but it feeds on things such as maggots, cutworms, and flies. It is a large black beetle with larvae that assists with composting and aeration of the soil.
  • Hoverfly. This is a fly often mistaken for a bee due to its yellow markings. The hoverfly is also known as the syrphid. These flies cannot bite or sting, but they can pollinate like a butterfly. They not only feed on mealy bugs, aphids, and a variety of other pests, but they have a fondness for parsley. 
  • Red or Yellow Lady Bug. This garden protector feeds on mites, aphids, thrips and scale. Once you’ve got them, you’ll need to keep them well-fed. These little beetles need small pests and pollen. The ideal sources for pollen would be cilantro, fennel, caraway, dill, marigold.
  • Assassin Bug.  A bug that eats a caterpillar is pretty awesome because caterpillars are virtually indestructible in the garden. The assassin bug is one for the job. It feeds on most insects, including the caterpillar, beetles, grubs, aphids, leafhoppers and more. 
  • Mites. There are good mites and bad mites. The thrips predator mite is clearly a good one. Spider mites feed on plant tissue, so they are bad. Learn more about which is which with a resource like this book (link to Amazon) or on a university extension website, like this one. 
  • Pollinators. Your pollinators are critical to the ecosystem, and this guy is chief among them. The bees and honeybees mandate flowers, meaning you’ll need to be sure to have them handy. Not to mention the other winged heroes, including moths, butterflies, flies, hummingbirds, and wasps who take care of our pollination.

Bugs can be your greenhouse garden’s savior or its demise. Believe it or not, it is within your control. When you dive headfirst into greenhouse growing, it takes much more than learning about taking care of plants and vegetation. 

There is an educational process involving the ecosystem as a whole and how it all functions. For the plants to thrive as they would in a natural environment, you need to take care of them as if they were being raised organically  – including making friends with predator bugs that can naturally wipe out the destructive pests. 

When you know the right bugs, you can skip the products and chemicals

Learning the various bug species and what their purpose is within the system is required with the work that you do as a horticulturist. Allowing the beneficial bugs into your surroundings is necessary for the livelihood of the vegetation, and in keeping the population of the nasty pests diminished. It’s a beautiful, natural life cycle that you’re responsible for creating within the walls of your greenhouse. 

So, while you can manage the population of “bad” bugs in the greenhouse, take care to keep the good ones around and they’ll do the work for you.

“ When we kill the natural enemies of a pest, we inherit their work off.” C. B Huffaker

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