Tips for Getting Rid of the Most Common Pests in a Greenhouse

A DIY greenhouse kit is a wonderful way to grow plants year-round, but it can also attract a variety of pests. Whether you’re dealing with aphids, spider mites, or other pesky insects, it’s important to take action to keep your greenhouse healthy and thriving. In this blog, we’ll share some tips for getting rid of the most common pests in a DIY backyard greenhouse.

7 Most Common Greenhouse Pests

We’ve curated a list of the most common ones you may encounter and proven ways to either prevent them from appearing or eliminate their presence.

These little devils are some of the most dangerous bugs that could find their way into your greenhouse.

1. Aphids

Aphids are tiny, soft-bodied insects that nest in clusters on the underside of leaves. Their feeding process literally sucks the life out of your plants as they suck the sap from the plant. This causes your plants to suffer from distorted leaves and stunted growth.

Aphids can be controlled by natural means, so you can maintain an organic planting environment. Introduce natural predators like lacewings and ladybugs to prey on aphids. Another option is to spray them with neem oil or wash your plants with insecticidal soap.

2. Spider mite

Spider mites are really small, eight-legged pests. These horrible creatures feed on the sap of plants, causing the leaves to yellow and molt. You can identify their presence from the tiny webs they spin between leaves. They should be prevented from entering the greenhouse space or removed immediately after being spotted as they will cause extensive damage if left unchecked.

Spider mites can be controlled by natural means and insecticidal soap. Wash your plants with insecticidal soap or spray them down with neem oil which is a natural pesticide. You can also control spider mites by introducing predatory mites like Phytoseiulus persimilis.

3. Whiteflies

Whiteflies are small, flying insects that nest on the underside of leaves. They damage your plants by sucking the sap from the plants. To compound their damage, they excrete a sticky substance that attracts other pests to your DIY backyard greenhouse. Additionally, they can lead to the growth of sooty mold.

Whiteflies can be controlled by using insecticidal soaps or neem oil to wash or spray down the plant. Another option to rid your greenhouse of whiteflies is by introducing natural predators like Encarsia formosa.

4. Thrips

These small, slender insects damage your crops by feeding on plant tissue. This feeding process causes silvery or bronze streaks on leaves. Thrips are additionally dangerous as they also spread viruses and other diseases to plants in your greenhouse.

Thrips can be controlled by introducing predatory mites like Amblyseius cucumeris to prey on them. Other effective ways to control Thrips is to spray them with neem oil cocktails.

5. Fungus gnats

Fungus gnats are small, flying insects that cause root damage to plants. These awful pests are attracted to moist soil and destroy your crops from down below. Fungus gnats also spread diseases and damage seedlings.

Fungus gnats can be controlled by allowing the soil in your garden bed to dry out between waterings. This will prevent constant damp soil for the gnats to thrive in. Yellow sticky traps are useful for capturing the adults and add beneficial nematodes like Steinernema feltiae to your soil to hunt and kill Fungus gnats.

6. Scale insects

These immobile pests are flat, and small and attach themselves to plants. They cause the leaves to yellow because they suck sap. Scale insects cause stunted growth and will eventually lead to the death of the plant.

Scale insects can be controlled by washing plants with insecticidal soaps or spraying them with neem oil. Introduce natural predators like Cryptolaemus montrouzieri to protect your garden from scale insects.

7. Mealybugs

Mealybugs are hard-to-control, soft-bodied insects covered in a waxy, white coating. These pests cause your leaves to yellow and the growth of your plants to be stunted.

Mealybugs can be controlled by introducing natural predators like the parasitic wasp Leptomastix dactylopii and Cryptolaemus montrouzieri. Neem oil is a natural remedy that works well against these pests.

How Companion Planting Can Help Keep Your Plants Healthy and Pest-Free

Another great way to repel and control pests in a small greenhouse for vegetables, or any greenhouse for that matter, is by growing great beneficial plants side by side with our main crops. Companion crops that either eat, kill, or repel pests can be planted in your greenhouse to great effect.

Carnivorous plants: Plants like the Venus Flytrap, Pitcher plants, and Sundews attract and capture insects. These guys will eat a lot of pests that’ll venture into your greenhouse.

Marigolds: Marigolds are greenhouse flowers that produce a scent that repels some garden pests like aphids. Planting them in your greenhouse will increase pollinators and repel harmful pests.

Garlic, chives, onions, escallion: Garlic, chive, onion, and scallion are natural insecticides and repellents. These herbs produce a scent that repels both spider mites and aphids.

Basil: The basil plant has essential oils that repel insects, including flies, and mites.

Lavender: In addition to its ability to soothe the nerve and help you relax, lavender is a natural insect repellent and is especially useful against moths.

Lemon Balm: This plant contains high levels of citronellal. Citronellal is the compound that gives it its lemony aroma and flavor. It is also the same compound that bugs find so unpleasant. It is a good repellent against gnats.

Rosemary: This herb is a natural insect repellent that works against flying insects like cabbage moths and other bugs.

Mint: This multipurpose herb is a great addition to any greenhouse garden or greenhouse nursery. The scent of mint repels, ants, mosquitoes, and moths.

Petunias: Petunias contain a chemical called limonene. This is a good repellent against destructive insects like aphids, tomato hornworms, and squash bugs.

14 Proven Methods to Prevent and Control Greenhouse Pest

You can actively take daily steps that can help reduce or prevent greenhouse pests. Here is a list of 14 things you can do:

1. Keep Your Greenhouse Clean
Regularly sweep/rake the floor, clean greenhouse shelves, and remove any dead or dying plant material. You should also clean any used pots or trays before storing them.

2. Introduce Natural Predators
Not all insects are bad. Some insects are natural predators like ladybugs, praying mantis, lacewings, and predatory mites. They will hunt and kill pests like aphids, spider mites, crickets, and thrips.

3. Use Sticky Traps
Hanging sticky traps is an effective way to catch flying pests. Hang them near your plants to attract and trap these pests.

4. Inspect Your Plants Regularly
Pests usually leave visible traces of their presence. Inspect your plants regularly to identify pest infestation. Whenever you notice something off or different, actively take steps to remove the pests.

5. Use Insecticidal Soaps or Neem Oil
It won't hurt to regularly spray your plants with Insecticidal soaps or neem oil. These natural concussions repel and remove pests like aphids, spider mites, and whiteflies.

6. Avoid Overwatering
Overwatering can lead to moisture buildup in the soil. Excess moisture can attract pests like fungus gnats. To avoid this, water your plants when they need it and allow the soil to dry out between waterings.

7. Get Separate Footwear
Using a separate pair of shoes for use inside and outside the greenhouse. This will avoid the introduction of pests from outside.

8. Use Reflective Mulch
Reflective mulch delays or prevents some flying insects from finding and infesting your plants. This mulch reflects ultraviolet light that confuses the insects' ability to locate their hosts. This trick affects winged aphids, whiteflies, thrips, and leafhoppers.

9. Use Diatomaceous Earth and Sticky Barriers
You can use sticky barriers like Tanglefoot around the base of larger plants to capture and kill crawling pests. Combine these with Diatomaceous Earth to get even more control over crawling pests like slugs, snails, and others.

10. Practice Crop Rotation
Rotating your plants will prevent pests from building up in the soil and help the soil recover between crops.

11. Put New Plants in Quarantine
If you are introducing plants from another location to your greenhouse, try to quarantine and clean them with antibacterial soap and neem oil before. This way they won’t carry new pests into your greenhouse.

12. Vacuum
You can use a household vacuum cleaner to remove pests from plants and other surfaces in your greenhouse.

13. Cover Openings
You should cover windows and door openings with netting to keep flying pests like aphids and whiteflies out of the greenhouse. Netting allows air and light into the greenhouse but keeps pests out.

14. Ventilate Adequately
Get roof and side vents to ensure your DIY backyard greenhouse has enough ventilation to discourage the buildup of humidity, which can attract pests.

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