Greenhouse Pest Control

[TEG Project Manager]

A greenhouse in the garden is like having your own piece of ideal summer weather at any time of the year. Unfortunately, this climate is also ideal for many pests that try to take up residence in your greenhouse and use your plants as a source of nutrients - nothing is more frustrating than when these tiny invaders damage the plants you worked so hard to grow.

Not only does a greenhouse provide perfect living conditions for many pests, but it is also free of natural predators that would normally help keep populations down.

These conditions provided by your greenhouse mean that it is imperative that you keep your pest situation under control and take action at the first sign of pest infestation.

Tips to keep in mind​

You can easily control pests in the greenhouse. It starts with being able to identify the types of pests that infest your growing space - and implement controls to prevent and eliminate them. Include these tips and techniques to try in your spring growing checklist - and follow them throughout the year. Here are some tips.

Common Greenhouse Pests​

Unfortunately, there are a plethora of different pests that would love to take up residence in your greenhouse. It can be difficult to spot these pests in the early stages, as most of them are very tiny - you may even see damage to the plants before you see the pests themselves. For this reason, there are some common pests you should watch out for, as early detection can make the difference between a simple pest control solution and a complex, time-consuming one.

Aphids​

Aphids are one of the most common greenhouse pests. They reproduce quickly and effectively terrorize any plants they find. These insects are small - usually smaller than a grain of rice - and tend to attach themselves to the leaves of your plants in groups, sucking out nutrients and damaging the plant. Newer leaves and younger growth are most at risk from aphids, although no green life is truly safe when aphids are present.

When a plant is infested with aphids, the most common signs of early damage are curled leaves or stems, yellowed leaves, stunted growth, or a sticky substance called honeydew. This honeydew often attracts ants, which can be another sign that aphids are around.

Greenhouse aphids are almost always exclusively female, as aphids have the ability to reproduce asexually, and males are only born under unfavorable living conditions. An asexually reproducing female can give birth to six to ten new aphids each day. New aphids are able to reproduce almost immediately, with many being pregnant before they are even born. The life span of an aphid is between 20 and 30 days, leaving lots of time for explosive reproduction.

Whiteflies​

Another common greenhouse pest to watch out for is the whitefly. Tomatoes, cucumbers and lettuce are usually among the first plants to be attacked by whitefly. Therefore, you should keep a special eye on these plants if you are concerned about whitefly. These insects are powdery white and fly in the adult stage, so they can easily move from one plant to another.

If your greenhouse is infested with whitefly, you may see signs such as yellowing and shriveling leaves. After some time, these leaves will die and begin to fall off your plant. Whiteflies do their damage by sucking the sap from the leaves. If enough whiteflies infest a single plant, it can cause the plant to die. Just like aphids, whiteflies leave honeydew that can attract ants.

Female whiteflies can lay up to 25 eggs at a time and generally lay an average of 150 eggs in their lifetime. The entire life cycle of a whitefly lasts between 21 and 36 days. During this time, they mature from a crawling insect that attaches to the underside of leaves to feed, to an adult insect that can fly and feed on any part of the plant - although they generally still prefer leaves.

Fungus Gnats​

With fungus gnats, you only have to worry about the larvae causing damage to your plants - although the adults tend to be a nuisance. Fungus gnats generally lay their eggs in the soil. Once the eggs hatch, the larvae search for food in the immediate area. Their food is often the roots of nearby plants. This means that your greenhouse plants are at risk if a nearby fungus gnat lays its eggs in the soil.

Fungus gnats thrive in a greenhouse environment and their larvae are more likely to harm your greenhouse plants than plants growing outdoors. In large numbers, fungus gnat larvae can cause stunted growth due to a damaged root system, sometimes resulting in plant death.

Adult fungus gnats fly and look very similar to mosquitoes - and they are just as annoying. If you see adult fungus gnats, there are almost certainly larvae in your soil as well.
The life of a fungus gnat is relatively short, and it spends more time as a larva than as an adult, which means it has more time to do damage to your plants. The eggs usually hatch in about three days if conditions are ideal, and once the larvae hatch, they spend the next two weeks feeding (during which time they cause plant damage).

In a short period of three to seven days, fungus gnats pupate before hatching as adults and living only about eight days - just enough time to lay eggs and harass anyone who enters your greenhouse.

Mealybugs​

Mealybugs are very similar in size and appearance to aphids, and in large numbers they are just as harmful to your plants. One advantage that mealybugs have over many other pests is a thick coat of waxy secretion that covers their entire body.

This whole-body secretion helps protect mealybugs from some contact insecticides. In many cases, a larger amount of insecticide is likely needed to penetrate their coating, which means you may need to reach for the spray bottle more often if you choose this type of pest control.

A properly set up greenhouse is a haven for mealybugs because the climate is their ideal habitat. These pests can feed on any part of your plants, and they are not particularly picky when it comes to variety. Depending on which part of the plant the mealybugs have targeted, your greens may suffer damaged or dead leaves, wilted and dead limbs, and even complete plant death if not dealt with quickly.

There are two species of mealybugs that are almost identical, but one gives birth while the other lays eggs. Both species have a life expectancy of about 88 days and can give birth or produce between 300 and 600 eggs during their lifetime. Mealybugs reproduce rapidly and in large numbers. They also live longer than many other similar pests, which means you will likely have several overlapping generations in your greenhouse at one time.

Controlling Common Greenhouse Pests​

Most greenhouse gardeners will encounter at least one type of pest in the course of their growing practice. Fortunately, there are a few ways to control these pests - some of which can even be used preventatively.

Introduce Ladybugs​

One of the main reasons pests can be so prevalent in greenhouses is the lack of natural predators that would normally feast on these pests on a daily basis. One of the most natural ways to control greenhouse pests is to introduce their natural predators, also known as biological control agents.

Ladybugs are not often thought of as predators, but in the insect world they scare mite-sized bugs. In a greenhouse, ladybugs can help control populations of aphids, whiteflies, fungus gnats, scale insects, mealybugs, mites and many other pesky insects.

In addition, ladybugs do not harm your plants or injure people or animals. Keeping a ladybug population in your greenhouse is an excellent preventative measure against pests. If you already have a pest infestation, you can safely lower the population rate with ladybugs.

Introduce Lacewings​

Similar to ladybugs, lacewings are another biological pest controller that control many pests that may infest your greenhouse. These beetles will not harm your plants and should not bother you while you are gardening in the greenhouse. One advantage lacewings have over ladybugs is that they are smaller than ladybugs, which means you are less likely to see them - although some gardeners like the look of ladybugs in their gardens.

Releasing lacewings in your greenhouse can greatly reduce the population of many pests such as aphids, whiteflies, fungus gnats, thrips, mites, leafhoppers and many others. In addition, lacewings reproduce quickly and create new generations of beneficial insects to take care of the pests you do not want.

Neem Oil Spray​

Neem oil acts as an insecticide when it comes into contact with certain small insects or their eggs. One of the main advantages of using neem oil over a stronger insecticide is that it is completely safe for humans (including children), pets and most beneficial insects.

Neem oil is generally purchased as a spray that can be sprayed on all plant parts and the soil in which they grow. However, neem oil must come in direct contact with the insects or their eggs to be effective, so you must be thorough in your application.

Greenhouse insects attacked by neem oil include aphids, whiteflies, fungus gnats, mealybugs, mites, thrips and others. It is important to use this product at the first sign of a greenhouse pest for optimal effectiveness. Neem oil can also be sprayed for prevention, because it is so safe to use.

Horticultural Soap​

Spraying your plants with a horticultural soap is another non-toxic way to control certain pests or even prevent them from harassing and harming your greenhouse plants. These soaps can be purchased or homemade and are generally made from petroleum or vegetable oils. Many gardeners feel more comfortable using these non-toxic soaps on their plants to reduce the risk of using potentially harmful chemicals.

While most gardening soaps are relatively inexpensive, it can be even cheaper to make them yourself - you probably already have all the ingredients you need. The most effective homemade horticultural soap is made by mixing one cup of cooking oil (vegetable oil, olive oil, peanut oil, etc.) with one tablespoon of dishwashing liquid (which does not contain degreasing agents) and one cup of warm water. This mixture can then be placed in a spray bottle to spray on your greenhouse plants.

Another version of horticultural soap, which can also be effective but may not last as long, is made by mixing one tablespoon of dishwashing liquid with one quart of warm water and placing the mixture in a spray bottle. This spray may need to be reapplied daily to get results, but it is one of the easiest to make.

Horticultural soaps such as those mentioned above are effective against most pests that infest the leaves of a plant. Pests that this soap is said to be effective against include aphids, whiteflies, mealybugs and spider mites - and many others. However, this method is not particularly effective against fungus gnats because the larvae stay too far underground and the adults are difficult to spray when they are flying around the room.

Chemical Pesticides​

Commercially available chemical pesticides are known for their effectiveness in controlling pests, including those in greenhouses. Some gardeners do not want to use these pesticides because of their toxicity, but some have little choice when their pest infestations become too extreme to control with natural or organic methods.

When using chemical pesticides in the greenhouse, it is especially important to leave the greenhouse until the chemicals have settled - you do not want to accidentally inhale them. If you apply these sprays outdoors, it's likely that the wind will dilute the chemicals that remain in the air. Once you have left your greenhouse for the recommended time (which varies by chemical and brand), you should open all windows and doors to ventilate the air for as long as possible.

Many foods we eat regularly have been sprayed with pesticides at some point along the way to our table. Eating food that has come in contact with these chemicals is not necessarily dangerous, but it is very important to make sure that the food has been properly and thoroughly cleaned. Many pesticides intended for growing crops have lower toxicity levels that are considered too low to harm humans, but it is still recommended that these crops be cleaned before consumption.

Conclusion​

As you read through this list of common greenhouse pests, you'll notice that many of the species listed are the same ones you'll find in lists of common pests for indoor and outdoor plants. Therefore, the golden rule of gardening applies here as well: be patient. It may take you some time to get rid of these greenhouse pests, and that's okay.

However, if you carefully check your plants every day and take the time to intervene when necessary, you can grow healthy, thriving plants in your greenhouse all year long - and without pests.

What types of pests have you dealt with in your greenhouse? Let us know in the comments!

 

[digitS']

Yes, the most common pest in my greenhouse is the aphid.

Neem oil and my homemade spray using dishwashing soap seem harder on garden plants than Safer insecticidal soap. So, that is the one that I may use for tender plant starts.

First, I'll use the mechanical technique of just pressing the discovered aphids with finger and thumb. The leaves are tender and aphids tend to drop off when there is danger. Both, limit effectiveness of this method.

I take them outdoors to spray. Tender leaves, never in direct sunlight, plants covered with spray -- the flats of plants are set in complete shade. Thoroughly sprayed with soap and allowed some time to dry, that's usually the end of a heavy infestation.

Steve

 

[calebgilk]

Hey there! I'm a newbie here. Stumbled upon your thread and thought I'd drop a line. Dealing with pests in the greenhouse can be a real bummer, but you've got some great tips for keeping those little suckers at bay. Aphids, man, those tiny little demons can really wreak havoc on your plants. It's crazy how fast they can reproduce and take over. I've also had run-ins with spider mites and whiteflies in my greenhouse, and those guys can be a real pain too. But like you said, patience is key when it comes to pest control. Daily check-ins and taking action as soon as you spot any issues can save you a lot of headache in the long run. Thanks for sharing!!

 

[Phaedra]

I am also dealing with aphids. I either use my fingers or bring the young plants out and use water to flush them away (also the surface layer of soil). As long as they are transplanted, the aphids usually become the prey in a short time.

Besides, aphids do attack those weaker seedlings. I will pay more attention to those weaker ones and usually remove the spent cotyledons.