How to Choose the Best Greenhouse Fumigator
Greenhouse fumigators can be used to ‘disinfect’ greenhouses.
This process can be done annually, before filling the space with plants, or when a particular problem is noticed – such as an insect infestation.
Some fumigators will act as both a fungicide and pesticide, whilst others are only aimed at getting rid of bugs.
Choosing the best greenhouse fumigator will depend on the problems you’re facing, as well as your personal view on using chemicals. The following information will help you make an informed decision.
Different Types of Fumigators
Fumigators for greenhouses come in the form of ‘candles’. They’ll have a wick to light, and should be sealed within the greenhouse to allow the smoke to properly fumigate the area.
The active ingredient can vary, which is what distinguishes between different fumigators.
Here’s a list of some of the commonly-found active ingredients in fumigators, with their advantages/disadvantages:
Sulphur Fumigators
Fumigators that contain sulphur are by far the most effective. Sulphur is a powerful and effective fungicide/pesticide and it will thoroughly disinfect the greenhouse. Whilst this all sounds great, there are some downsides.
As you may have guessed, sulphur fumigators are very harsh, and these types of chemicals shouldn’t be used lightly. All plants will need to be removed from the greenhouse, and no-one should breathe in the smoke.
It’s extremely important to follow the instructions carefully (as with all products!) to make sure no health problems ensue from using sulphur-based fumigators.
Additionally, when sulphur burns, it turns into sulphur dioxide. This gas can react with water to form acid and can have a damaging effect on plants.
Sulphur also smells very strongly, so be aware of this when using it in your garden.
Permethrin Fumigators
Permethrin is an insecticide. It will not tackle any fungal spores inside the greenhouse. However, it is effective at killing a broad range of insects, which is what makes it useful as a fumigator.
Permethrin is considered less toxic than sulphur, although it can still cause health problems so the product instructions must be followed closely. It’s considered extremely toxic to aquatic life.
Whilst generally not as effective as products that contain sulphur, fumigators with permethrin as the active ingredient can work well.
Garlic (Natural) Fumigators
Not all fumigators contain harsh chemicals, and some rely on garlic oil as the active ingredient to flush insects out. Some insects will be killed by the fumigation, and others will be dissuaded from returning by the properties of the garlic.
Whilst not the strongest of fumigators, it can be good to use natural products at least as a first line of defence. If they don’t work, you may have to move onto something stronger (and harsher), but it’s worth trying first.
Natural products generally don’t harm plants, and can be used whilst plants are in the greenhouse (but, as always – check the instructions of the specific product!).
Preparing to Fumigate
Once you’ve decided to fumigate your greenhouse, there are a few steps to follow to make sure the process is as efficient and safe as possible.
- Seal your greenhouse well. If smoke can escape, it won’t fumigate properly. The smoke might also might hang around in the garden, particularly if it’s a still day, and disturb you or your neighbours (you certainly don’t want the smell of sulphur or garlic getting on anyone’s clean washing!).
- Remove plants from the greenhouse (this step may be optional if you are using a fumigator with natural ingredients – check the instructions!). Most people fumigate their greenhouse during the winter months so that they can safely put plants outside without killing them. If you need to fumigate when it’s cold out, you’ll need to prepare somewhere warm for your plants. Fumigating can take 12 hours +.
- Make sure no-one needs to enter the greenhouse for any reason during the whole fumigation process. Until the greenhouse has been properly ventilated, after fumigating, don’t allow anyone inside.
How Many Fumigators to Use
Generally speaking, one fumigator will be sufficient for a standard 2.4 x 1.8 m (8 x 6 ft) greenhouse. However, the instructions for individual products may state otherwise, so be sure to check them first – some products may work over larger or smaller spaces. It’s also a good idea to check customer reviews, to see how the products performed in real life. This can give a good indication of how many fumigators to buy for your particular greenhouse.
Although it may not seem immediately obvious, you can use more than one fumigator. Therefore, if you have a larger space to fumigate, you may want to consider using two or even three fumigators. Select the number of fumigators you require based on the size of your space and the product instructions – using an excessive amount will just waste money and could even be dangerous.
Greenhouse Fumigator FAQs
How do you use a greenhouse fumigator?
You should always carefully follow the specific instructions on your fumigator for safe use. Here are some general outlines:
- Depending on the type of fumigator you may need to remove all plants from the greenhouse. This will be the case if you are using a sulphur candle; however, for some products it will not be necessary.
- Close the windows and doors of your greenhouse.
- Place the fumigator candle on a fireproof surface, such as a brick, in the middle of the greenhouse. If you are using more than one, space them out evenly.
- Light the candle then leave the greenhouse, closing the door behind you. Wait outside to check that the candle is lit, and smoke is being produced. Sometimes it can be fiddly to get the wicks of these to light so you might have to go back in and relight it.
- Once the candle is smoking you can leave it to do the job. Follow the instructions on the fumigator to know when to open the doors and ventilate the space. You should not enter until it is completely ventilated which may take a full day.
Are sulphur fumigators bad for the environment?
Sulphur fumigators can have a negative impact on the environment. Burning sulphur releases a gas called sulphur dioxide. When this mixes with moisture, it can form acid. Therefore, if it mixes with water droplets on plant leaves, for example, it can burn them.
Additionally, breathing in sulphur dioxide can be very dangerous. When using a sulphur fumigator, utmost care must be taken not to breathe in any of the fumes. This applies to all animals.
How often should I fumigate my greenhouse?
Many gardeners choose to annually fumigate in order to keep on top of any problems. This is often done around Autumn, when plants can still be outside, but winter is just around the corner. You can also fumigate if there is a particular problem – such as an insect infestation – that you feel needs to be dealt with.
