Pest Control in the Greenhouse
Pest control in the greenhouse - what do you have to watch out for?
Having a garden greenhouse is like having your very own slice of ideal summer weather any time of the year. Unfortunately, this climate is also ideal for many pests that will try to make a home of your greenhouse, using your plants as their source of nutrients—nothing is more frustrating than having these tiny invaders harm the plants you’ve worked so hard to raise.
Not only does a greenhouse create perfect living temperatures for many pests, but it is also free of natural predators that would generally help keep populations low.
These conditions provided by your greenhouse mean that it is crucial to keep your pest situation under control and take action at the first signs of pest-related damage.
Pest Control in the Greenhouse: Tips to Follow
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You can easily deal with pests in the greenhouse. Doing so starts with being able to identify the kinds of pests that are infesting your growing space - and enacting controls to prevent and eliminate them. Add these tips and techniques to try to your spring gardening checklist - and follow them throughout the year.
Here are some tips.
How Do You Control Pests in a Greenhouse?
A few ways to control pests in a greenhouse are:
Introduce ladybugs or lacewings
Try neem oil
Use horticultural soap
Try a chemical pesticide
Most importantly, be sure to plan ahead. This garden planning chart can help, as can some of the tips in the video below:
Common Greenhouse Pests
Unfortunately, there are an abundance of different pests that would love to make a home of your greenhouse. Spotting these pests can be difficult in the early stages, as most of them are very tiny—you may even see plant damage before you see the pests themselves. Because of this, there are some common pests you should watch for since early detection can make the difference between a simple pest control solution and a complex, more time-consuming one.
Aphids
Aphids are one of the most common greenhouse pests and are quick to multiply, effectively terrorizing any plants they can find. These insects are small—generally smaller than a grain of rice—and they tend to attach themselves to the leaves of your plants in clusters, sucking out nutrients and harming the plant. Newer leaves and younger growth are most at risk to aphid infestations, although no green life is truly safe when aphids are around.
When aphids infest a plant, the most common signs of early damage include curling leaves or stems, yellowing leaves, stunted growth, or a sticky substance referred to as honeydew. This honeydew will often attract ants to the area which can be another sign that aphids are near.
Greenhouse aphids are almost always exclusively female, as aphids have the ability to reproduce asexually and males are only born in undesirable living conditions. An asexually reproducing female can give birth to six to ten new aphids every day. New aphids are able to start reproducing almost immediately, with many already pregnant before they are even born. The lifespan of an aphid is between 20 and 30 days, leaving plenty of time for explosive reproduction.
You can find more information about dealing with aphids here.
Whiteflies
Another fairly common greenhouse pest to watch for are whiteflies. Tomatoes, cucumbers, and lettuce are generally some of the first plants that a whitefly will attack, meaning these plants are especially important to keep an eye on when worried about whiteflies. These insects are a powdery white color and fly in their adult stage, so they can easily move from one plant to another.
If whiteflies are in your greenhouse, you may see signs such as yellowing and shriveling leaves. After some time, these leaves die and start to fall off your plant. Whiteflies cause their damage by sucking the juices from leaves. If enough whiteflies infest a single plant, it can lead to death of that plant. Just as aphids do, whiteflies also leave behind honeydew which may attract ants.
Female whiteflies can lay up to 25 eggs at once and will generally lay an average of 150 eggs in their lifetime. The entire life cycle of a whitefly will last between 21 and 36 days, and in this time frame, they will mature from a crawling insect that attaches to the undersides of leaves to feed, to adult insects that can fly and feed off of any part of the plant—although they still generally prefer leaves.
For additional information on whiteflies along with some other common greenhouse pests, visit this link.
Fungus Gnats
When it comes to fungus gnats, you only need to worry about the larvae causing damage to your plants—although the adults do have a tendency to be annoying. Fungus gnats generally lay their eggs in the soil, so once the eggs have hatched, the larvae will look for food in the immediate vicinity. Many times, their food ends up being the roots of any plants nearby, meaning your greenhouse plants are at risk if a fungus gnat lays eggs in the soil nearby.
Fungus gnats thrive in a greenhouse environment, and their larvae are more likely to cause harm to your greenhouse plants as opposed to plants that are grown outside. In large quantities, fungus gnat larvae can cause stunted growth due to a damaged root system, sometimes resulting in the death of the plant.
The adults fly and look very similar to mosquitoes—and they are just as pesky. If you notice adult fungus gnats, there are sure to be larvae in your soil.
The life of a fungus gnat is relatively short, and they spend more time as a larvae than they do as adults—translating to more time to cause harm to your plants. Eggs generally hatch in about three days if conditions are ideal, and once the larvae have hatched, they spend the next two weeks eating (this is when they cause plant damage).
There is a short time of between three to seven days when the fungus gnats are in a pupal stage before they emerge as adults, living only about eight more days—just enough time to lay eggs and bother anyone who enters your greenhouse.
Here’s a source with more information on fungus gnats.
Mealybugs
Mealybugs are very similar in size and appearance to aphids, and they are equally as harmful to your plants in large quantities. One advantage that the mealybug has over many other pests is a thick coat of waxy secretion that covers its entire body.
This full-body secretion helps protect the mealybug from some contact insecticides. In many cases, a larger quantity of insecticide is likely required to penetrate their coating, meaning you might have to get the spray bottle out more often if that is the pest control route you are taking.
A properly set up greenhouse is paradise for mealybugs as the climate is their ideal living situation. These pests can feast on any portion of your plants, and they aren’t particularly picky when it comes to variety. Depending on what part of the plant the mealybugs have targeted, your greenery may experience damaged or dead leaves, wilting, dead limbs, and even complete plant death if action is not taken soon enough.
There are two species of mealybugs that are nearly identical, but one gives birth while the other lays eggs. Both species have a lifespan of approximately 88 days and can give birth to or produce between 300 and 600 eggs within their lifetime. Mealybugs reproduce quickly and in large quantities. They also live longer than many other similar pests, meaning you are likely to have multiple overlapping generations in your greenhouse at once.
How to Control Common Greenhouse Pests
Most greenhouse gardeners will encounter at least one type of pest within their growing career. Thankfully, there are some options when it comes to controlling these pests—some of which can even be implemented as a preventative measure.
Introduce Ladybugs
One of the main reasons why pests can be so prominent in a greenhouse environment is because it lacks the natural predators that would normally be feasting on these pests daily. One of the most natural ways to control greenhouse pests is to introduce their predators, sometimes referred to as biological control agents.
Ladybugs are not often thought of as predators, but in the insect world, they strike fear into the hearts of mite-sized bugs. In a greenhouse, your ladybugs can help to control the populations of aphids, whiteflies, fungus gnats, scales, mealybugs, mites, and many more pesky insects.
Furthermore, ladybugs won’t cause any harm to your plants, and they don’t hurt people or animals either. Keeping a population of ladybugs in your greenhouse is a great preventative measure against pests. If you already have an infestation, adding ladybugs is sure to help lower the population rates.
Introduce Lacewings
Similarly to ladybugs, lacewings are another biological control agent that are a predator to many pests that may infest your greenhouse. These bugs won’t hurt your plants and shouldn’t bother you when you are in your greenhouse gardening. One advantage to lacewings over ladybugs is that they are smaller than ladybugs, meaning you are less likely to see them—although some gardeners like the look of ladybugs in their garden.
Releasing lacewings into your greenhouse can greatly reduce the population of many pests including aphids, whiteflies, fungus gnats, thrips, mites, leafhoppers, and many more. Lacewings are also quick to multiply, creating new generations of beneficial insects to take care of the ones you don’t want around.
Neem Oil
Neem oil acts as an insecticide when it comes in contact with certain small insects or their eggs. One of the primary benefits of using neem oil as opposed to a stronger insecticide is that it is perfectly safe for humans (including children), pets, and most beneficial insects, so many gardeners feel better about using it on their edible plants and crops.
Neem oil is generally purchased as a spray that can be spritzed on all parts of the plants and the soil they are growing in. However, neem oil does have to directly come in contact with the insects or eggs to be effective, so you need to be thorough when using it.
Greenhouse insects that are affected by neem oil include aphids, whiteflies, fungus gnats, mealybugs, mites, thrips, and more. It is important to use this product at the first sign of a greenhouse pest to be the most effective. Neem oil can also be sprayed as a preventative measure since it is so safe to use.
Horticultural Soap
Spraying your plants with a horticultural soap is another non-toxic way to take care of or even prevent certain pests from bothering and harming your greenhouse plants. These soaps can be purchased or made at home and generally consist of petroleum or plant oils. Many gardeners feel better using these non-toxic soaps on their producing plants to reduce the risk of consuming potentially harmful chemicals.
While most horticultural soap is relatively inexpensive, it may be even cheaper to make it at home—you likely already have all of the ingredients you need. The most effective homemade horticultural soap is made by combining one cup of any cooking oil (vegetable, olive, peanut, etc.) with one tablespoon of dish soap (one that does not contain degreaser) and one cup of warm water. This mixture can then be added to a spray bottle to be sprayed on your greenhouse plants.
Another version of horticultural soap that can also be effective, but may not be potent as long, is created by combining one tablespoon of dish soap to one quart of warm water and adding the mixture to a spray bottle. This spray may need to be reapplied daily to get results, but it is one of the simplest to make.
Horticultural soaps such as the ones mentioned previously are effective on most pests that affect the leaves of a plant. Some pests that this soap is said to be effective against include aphids, whiteflies, mealybugs, and spider mites—along with many others. However, this method is not particularly effective against fungus gnats because the larvae stay too far under the soil and the adults are hard to spray when they’re flying around the room.
Do You Need Pesticides in a Greenhouse?
Store-bought chemical pesticides are known for their effectiveness against controlling pests, including those in a greenhouse environment. While some gardeners are not comfortable using these pesticides due to their toxicity, some are left with little to no other choice if their pest infestation becomes too extreme to handle with natural or organic pest control methods.
When using chemical pesticides in a greenhouse setting, it is extra important to stay out of the greenhouse until the chemicals have settled—you don’t want to accidentally breathe them in. When applying these sprays in an outdoor environment, the wind is likely to move and dilute the amount of chemicals that stay in the air. Once you have left your greenhouse for the recommended amount of time (which varies by chemical and brand), make sure to open any windows and doors to create ventilation as long as possible.
Many foods that we eat regularly were sprayed with pesticides at some point along the process to our tables. Food that has been in contact with these chemicals is not necessarily dangerous to eat, but it is very important to make sure the food has been cleaned properly and thoroughly. Many pesticides designed for producing plants have a lower level of toxicity that is said to be too low to harm humans, but cleaning these crops before eating is still recommended.
How Do Greenhouses Stay Pest Free?
In reading through this list of the most common greenhouse pests, you'll see that many of the species on the list are the same ones you might find on lists of common indoor or outdoor plant pests.
Therefore, the same golden rule of gardening applies here - be patient. It might take some time for you to get rid of these greenhouse pests, and that's okay.
However, by inspecting your plants carefully each day and taking the time to enact interventions when necessary, you will be able to grow healthy, thriving crops in your greenhouse year-round - and pest free. And another one of the best ways to get ahead? Be sure to plan out your plantings and pest control measures carefully. By being organized, you can keep most of your pest problems at bay. Here’s a helpful garden planning chart you can use to help you stay on top of things.
What kinds of pests have you had to deal with in your greenhouse? Be sure to let us know in the comments!
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