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Greenhouse Gardening Organic Pest Control – Caterpillars

A striped colored caterpillar crawling on a leaf with the text Organic Pest Control Caterpillars

Table of Contents

Caterpillars can be harmful, and not each of them turns out to be flying like Monarchs. Do a little research. Determine what sort of caterpillars you have. Gypsy Moth and Redhumped caterpillars are the actual pests. They can strip leaves in a short time. Keep reading to find ways to organically control caterpillars in your greenhouse.

Caterpillars are the larvae of moths and butterflies. The term also describes the larvae of other insects such as sawflies. Most caterpillars are herbivorous, though about 1% of them are insectivorous.

A hairy caterpillar crawling on a flower stem

The most distinctive features of caterpillars are their hairy, segmented bodies, three pairs of legs, and five pairs of prolegs. They move as if they are measuring the length of their track. These crawlers are voracious feeders that can easily strip your greenhouse plants of all their leaves and in the process, leading to reduced plant vigor.

Organic methods to eliminate caterpillars in your greenhouse

Use one of the following organic pest control methods in your greenhouse quickly before they ruin your harvest.

Use Bacillus thuringiensis (Bt.)

This free occurring bacterium lives in the soil and is effective in eradicating caterpillars. During sporulation, it produces delta endotoxins (pore-forming toxins) that are harmful to caterpillars and other pests. The dilution percentages carrying the bacteria may vary depending on the plant you are preparing to spray. Read thoroughly and understand the manufacturer’s directions for blending and applying pesticides.

Bacillus thuringiensis or Bt. is a bacterium that is not poisonous to humans and mammals but it is lethal to some insects like caterpillars when ingested. The EPA and various scientific organizations have found that Bt and engineered Bt-crops are not fatal to humans. It is typically found on the leaves and in soil worldwide. It has been used commercially in organic and traditional agriculture for more than fifty years.

Covering method

Plant coverings can efficiently shield your plants from caterpillars. Place the cover above the crop. This approach is not suitable for crops that demand pollination.

Practice crop rotation

Growing crops, in turn, is an effective strategy in controlling caterpillar infestation in greenhouses. For instance, after good harvest of tomatoes, you may consider planting coriander.

To intimidate and distract caterpillars, do not grow plants in the related species collectively in the very place every year. You can alternate your rows of greens or rotate crops throughout your greenhouse each season.

A bird with a green caterpillar on its beak

Beneficial insects and birds

Ducks and chickens enjoy feeding on caterpillars, so do praying mantises. You can invite your hens into the greenhouse so they can help with biological control. If you live in an environment that has praying mantises then these too can help. You can encourage birds to perch around your greenhouse by building feeding areas. Although it is a slower method than spraying, promoting a variety of wildlife to visit your greenhouse is a beneficial long-term tactic for defeating caterpillars and other pest invasions. Note: You will obviously need enough escape openings so that birds can easily find their way out. If you only have a small door and a roof vent, don’t invite birds, as they might get trapped.

Natural pesticides

Natural pesticides are better since they have fewer side effects. These pesticides are made from plants. It breaks down quickly, unlike synthetic chemicals. Some are organic techniques that are very helpful in combating pests.

Sage, peppermint, mugwort and lavender, all produce scents that repel caterpillars effectively. Therefore, consider planting one or two of these plants when setting up your greenhouse. These home remedies are effective repellents.

Garlic has a naturally acidic essence that can eliminate caterpillars. Combine two cups of water including two spoons of garlic powder in a spray bottle. Add a spoon of dish soap. Sprinkle the solution to the affected area.

Hot pepper is another natural caterpillar repellent. Crush and dash some hot peppers throughout your garden. You may also create a chili spray formula by combining two cups of water, two spoons of hot pepper powder, and a spoon of dishwashing soap. Sprinkle it on your plants. You can spray the solution every couple of weeks or after a rainfall.

Neem oil is a natural insecticide. It is formulated using essences from its seeds. Organic sprays carry bacteria that tackle the pest but are not toxic to humans and pets. Neem oil is lethal to bees. Spray it after dusk when the bees are no longer active.

A green caterpillar on two hands


Handpicking technique

You can patrol the greenhouse either during the day or at night and handpick caterpillars off the plants. Use burlap for your fruiting trees. Wrap the trunk with a burlap. The caterpillars will surely crawl under it when they need shade. Once they are all there, you can remove the burlap and handpick them. Consider relocating the picked caterpillars to some location where they will cause little damage.

When you notice just one caterpillar, inspect your plant for more which may be on a different leave or plant. Take off all the caterpillars you can see, place them somewhere far away, or crush them. Pick off the entire leaf and destroy it if your plant has more leaves. Repeat it every day. Handpicking may not be as effective as other methods but it is definitely a way to reduce or eliminate these caterpillars.

What caterpillars are dangerous to crops?

Gypsy moth is an invasive caterpillar. They are commonly known as the exfoliator pest. They tear the leaves of a plant. You will see them feeding on apple, oak, and willow trees. The adult caterpillar will eat the leaves from the outer side inwards and leave almost nothing. The young ones will penetrate small openings in the middle of the leaves they eat.

The Redhumped caterpillar usually eats leaves. It feeds on plum,  apple, walnut, cherry, and other deciduous trees and plants. Newborn caterpillars generally feed side-by-side in clusters. They will chew the lower leaf part. Then they will manage to disperse as they develop and sustain themselves in smaller groups or independently.

Skeletonized leaves are the most common outcome. Insecticide applications can be used only if there are a lot and their damage is unbearable. Biological control can also help manage these kinds of invasion. Spot pruning is effective if there are a few of them.

Are there any beneficial caterpillars?

Some caterpillars are beneficial insects. They will become butterflies or moths, which are essential pollinators. If you notice some caterpillars in your garden, remember that only a few species are the actual pests.

A monarch butterfly on a flower

One of the most noticeable is the Monarch.

. They only consume milkweed and they mean no threat to your plants. As a matter of fact, gardeners are doing their best to attract them.

A friendly caterpillar called Cecropia poses no risk to your plants. It is roughly as long and thick as your finger with neon green and multi-colored spiked knobs. Thankfully, the spikes are not harmful when touched. They have plenty of hunters that is also another reason why they don’t usually become a pest. The adult caterpillar has no functioning mouthparts, so its only purpose is to mate.

Have you tried any of these methods to remove caterpillars? Tell us more by leaving a comment below!
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