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Rid Your Greenhouse of Common Pests: the Organic Way

By: Lucy Debenham BA (hons) - Updated: 26 Sep 2012 | comments*Discuss
Greenhouse Pests Organic Hygiene Tidy

Of course, the warm and sheltered greenhouse is the perfect environment for seedlings and plants. However, this is also what makes a greenhouse the perfect home and breeding ground for all manner of pests. However, because the environment of the greenhouse is essentially contained, you can also easily contain and manage your pest problem relatively easily too.

Keep it Clean!

The first step to ridding your greenhouse of common pests the organic way, is to try and maintain a generally good level of hygiene. Your best bet is embark on the early winter months by establishing a strict hygiene regime, making sure that any pests that use your greenhouse as an overwintering spot are removed before they have a chance to begin breeding in the warmer spring months.

It should only take you a couple of days to undertake a thorough clean. For this reason, you might need to temporarily move out any plants that grow throughout the year in your greenhouse, as well as any plants or bulbs in storage. If you grow directly into the soil inside your greenhouse, be sure to protect or remove the bulbs from the soil before starting your cleaning regime.

Keep it Tidy

Once your greenhouse has been emptied, you should take the opportunity to reorganise the layout if required, and throw out or recycle anything that you don’t use. This is because stacked module trays, pots or piles of used compost bags and seed packets can all become handy shelters for many different types of pests. Removing them removes the extra hygiene management issues!

Outside and In

The first step to organic pest control is to give your greenhouse a wash down, both inside and out. If you’re keen to keep your pest management strictly organic, then using a plant-derived environmentally-friendly household detergent on a soft broom is probably your best option. Try and choose a dry or bright slightly breezy day for your wash down – blasting the outside of the greenhouse with a hosepipe will help to remove grit and grime before you wash down with your soapy soft broom. You might find that you’ll need to do a second outside wash down around spring for optimum results.

When cleaning the inside of the greenhouse, pack away your hose and you won’t need it, especially if your greenhouse has electrical installations or outlets. For your safety, any electrical plugs should be switched off at the mains or the source of the supply.

Your first task is to tackle the greenhouse glass panes – removing grime, algae, moss and dirt from each pane may take a while, but is a worthwhile job. Be sure to pay attention to any areas where the glass or glazing bars overlap. You could try giving everything a brush down with a stiff brush, making sure to dislodge spiders or any other ‘friendly’ overwintering insects that wouldn’t benefit from a wash down!

You’ll also need to clean any slabs and greenhouse staging with your environmentally-friendly household detergent solution. Once everything has been thoroughly cleaned, rinsed and dried, you can then put up any insulation for the winter if required. Lastly, don’t forget to thoroughly clean and try any tools or equipment too.

Before you bring your plants back into the greenhouse, make sure to check them each thoroughly for signs of pests and diseases.

Organic Pest Control

So it seems one of the key elements of organic pest control is preparation, elbow grease and regular maintenance! However, Mother Nature often has a way of overcoming even the most regimented cleaning schedules, so you may find that occasionally, you have to undertake a spot of actual pest control, rather than prevention, in your greenhouse.

Here we look at some of the most common greenhouse pests, and how you can rid your greenhouse of them organically.


Aphids are perhaps the most well-known and prolific greenhouse pests. The most effective pest control method is regular checks for aphids, and rapid removal. You can either remove them by spraying with an (organic) soapy solution, or alternatively purchase and introduce a natural aphid predator, such as the parasitic wasp (Aphidus) or predatory midge (Aphidoletes). You can also try to encourage natural predators from your garden; lacewings, hoverflies and ladybird larvae will all help to diminish any aphid populations.

Sciarid Flies

Sciarid flies prefer to lay their eggs in peat-based composts. Here, the grubs hatch and feed on the roots of plants, with young plants being particularly vulnerable. In cases like this, the best course of action is to remove all compost and completely re-plant, making sure not to over-water the new peat-based compost.


A tidy greenhouse will reduce the likelihood of slugs moving into your greenhouse. However, if any do make their way in, you should firstly pick them off and remove elsewhere. Remember that slugs have natural predators such as hedgehogs and birds, who, if encouraged into your garden, will help you to manage them.

One organic solution is to put copper rings and tape around your plants and pots. Gravelling around or inside your greenhouse will also add an extra obstacle to the slugs’ progress.


Whitefly is another well-known notorious greenhouse pest. Infestations can be organically managed and tackled with the introduction of another predatory wasp Encarsia Formosa. The predatory wasp’s eggs are embedded into strips of leaves, which can be left in the greenhouse to hatch out. Whilst they may not entirely remove your whitefly problem, they will certain make a noticeable difference, and prevent sooty mould. Additionally, it has been suggested that marigolds may help to repel adult whitefly.

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