Running an entirely organic site means we cannot reach for a bottle of something when things go wrong. Over nine seasons we have developed a short list of methods that actually make a difference, and a longer list of things we tried and stopped doing. Here is the honest version.
Slugs: the permanent problem ¶
Slugs are the thing we get asked about most. The methods that work for us are: copper tape around the base of raised beds (effective but expensive to do at scale), going out after dark with a torch and removing slugs by hand (unglamorous but genuinely effective), and encouraging ground beetles by leaving some areas of the site undisturbed. Slug pellets based on ferric phosphate are approved for organic use and do work, but we use them sparingly and only around the most vulnerable seedlings.
Aphids: neem oil and patience ¶
We use a diluted neem oil spray on aphid-affected plants, applied in the evening to avoid harming visiting insects. It works by disrupting the aphid's life cycle rather than killing on contact, so it takes a week or two to show results. For heavy infestations, a strong jet of water to knock aphids off the plant is faster and costs nothing. Ladybird larvae are more effective than either, but you cannot order them.
Whitefly in the polytunnel ¶
Whitefly is our main polytunnel pest, particularly on tomatoes and cucumbers. Yellow sticky traps catch adults and give you an early warning of population levels. We also introduce Encarsia formosa, a parasitic wasp available from biological control suppliers, in late May each year. It is not cheap (around £12 for a card of 500 pupae) but it keeps whitefly populations below damaging levels through the summer.
The thing that helps most ¶
Healthy soil grows healthy plants, and healthy plants resist pest pressure better than stressed ones. This is not a mystical claim. A plant that is well-fed, well-watered, and growing in good soil has thicker cell walls and more immune responses. The best pest control we do is the composting, the green manures, and the soil care that happens every winter.
Organic pest management is not about finding a substitute for chemicals. It is about building a system where pest pressure stays manageable. It takes a few seasons to get there, but it does get easier.