The warmth, shelter and food in abundance that a greenhouse offers can become a veritable haven for pests of all shapes and sizes. There are a number of ways to try and prevent the spread of pests within your greenhouse, but unfortunately not all of them are particularly environmentally friendly.
By choosing organic rather than chemical pest control, the likelihood is that you’ll strike a balance that needs little intervention or management. Organic pest control also makes sure that you target the problem, rather than undertaking a blanket attack on ‘good’ and ‘bad’ bugs, which can store up problems later on.
This article takes a look at some basic organic methods that you can attempt in order to repel and control pests within your greenhouse.
Companion Planting Schemes
Nature is very good at knowing how to address balance, so it should come as no surprise to learn that she also has her own pest control systems. In terms of pest control, companion planting is one principle that employs entirely organic means to help manage and prevent pests. It works on the ethos that by planting certain flowers or herbs alongside other plants or vegetables, problem pests and parasites will either been drawn away or repelled from the plant.
For instance, nasturtiums are often planted to draw away black and woolly aphids from plants and trees. Alliums such as onions and leeks are also often planted alongside carrots, as they are known to deter carrot fly. Interestingly, carrots are also thought to deter leek moth and onion flies!
Companion planting is definitely one such means of organic pest control that you can adapt in your greenhouse. Tomatoes are a popular greenhouse-grown fruit that often suffer from greenfly and blackfly attacks. To help repel these pests, you can plant French marigolds at the base of the plants. The scent of the marigold is enough to ward off pests, leaving the tomato plants in tact.
Other useful companion planting schemes include buddleia, achillea and flowering herbs such as hyssop, dill, rosemary and lavender to attract pest-devouring ladybirds, lacewings and hoverflies.
Interestingly, companion planting extends beyond the realms of insect pest control. Mice can be problematic in greenhouses, able to do untold damage to plants in the space of a few hours overnight. The scent of elder is thought to deter mice, and a small common elder shrub can be easily planted and kept in a pot inside a greenhouse, and may prove to be a complete eco-friendly, humane pest control method.
If you’re not too squeamish then you can also leave down humane traps for mice and rats. However, you will need to release these animals at least a mile from ‘home’ (and preferably not straight into someone else’s back garden!) in order to make sure that they don’t return. If you’re fond of these mammals, and subscribe to the ethos of ‘live and let live’, then leave them somewhere with plenty of natural food supplies, such as wild berries.
If all or part of your greenhouse floor is directly onto soil, you may experience a problem with ant nests. Peppermint, bay leaf, garlic, penny royal and spearmint are just a few herbs and plants that are recommended to keep ants at bay. Tansy is another popular ant repellent. You can either plant the herbs directly into the ground, keep in pots, or make up a solution using water and essential oils/extracts from the herbs.
This area of organic pest control is rapidly expanding. It basically works by using small organisms to systemically attack larger pests, such as slugs. The nematodes are mixed with water and fed to plants and surrounding areas where the pest may come into contact and feed.
However, in a greenhouse, slugs and other larger ‘pests’ that warrant control via nematodes shouldn’t be too much of a problem, provided your preventative measures are good enough in the first place.