1st July 2016

Natural pest control in organic growing

By Rob Alcock

When you're working hard day to day to grow crops and keep gardens looking good, even as an organic gardener it's sometimes easy to forget quite how incredible and perfect nature is. I always make the assumption that nature left to it's own devices will find a balance, and this is undoubtedly true, but it doesn't always right itself before a bed of seedlings or young plants are munched by slugs and snails (especially this year), or white rot wipes out your garlic. So you need to be vigilant, and to know when, and how to intervene and when to let biology take its course. 

If you don't mind the odd hole in your lettuce, is it a problem? Organic growing at Sheepdrove Organic Farm

In fact gardening is all about intervention; weeding, planting, mowing, pruning...otherwise the chances are that you'll end up with woodland in time. But an organic gardener has to take a different perspective to the often instinctive human desire to annihilate any perceived threat to their perfect petunias. 'Always spray your roses so blackspot and greenfly can never make an appearance...use a weed and feed on your lawn...' great advice for selling chemicals but at what cost? I think the trick is to know when something is really a problem and when it's not. If you don't mind the odd hole in your lettuce, is it a problem? It's all a matter of perception and experience.

Organic growing through the seasons

We have one big polytunnel at Sheepdrove situated within our gardens which also grow herbs, berries and flowers for Neal's Yard Remedies. The polytunnel enables us to grow earlier crops in the Spring, salad through the Winter and heat-loving crops like tomatoes, aubergines, peppers and courgettes in the Summer - great for supplying fresh plot-to-plate salads and veg to our conference centre kitchen. We grew curly parsley in there through the Winter and it got absolutely covered in aphids(greenfly) as the days got warmer. It's a tough old plant though, and they didn't seem to be harming it at all, so all that was needed was for the kitchen to wash off the tiny dry skins of the already departed bugs.

Encouraging ladybirds for pest control

As Spring carried on, more and more ladybird larvae appeared on the parsley which by now was in the process of flowering (great for attracting hoverflies - another predator). Ladybirds must have laid eggs on the plants knowing that there were plenty of aphids for their young larvae to feed on. Now here's the interesting thing; when we planted sweet peppers ( a crop famously prone to aphids) on neighbouring beds, the larvae moved across and placed themselves almost exactly one on each pepper plant, and started pupating - the process of transforming into the adult ladybird. Somehow both adults and larvae know what plants are going to attract aphids in advance of them being there, and position them ready to do our pest control for us! Aphids probably would be more of a problem on peppers and aubergines, feeding on and distorting the growing tips and possibly spreading viruses.

Key to success in organic farming and growing

This also highlights one of the keys to successful organic farming and growing - avoiding monocultures. Without a mixture of crops at different stages of growth this couldn't happen. Pests and diseases can run wild through large areas of single crops, one of the reasons much modern farming is hooked on chemical controls. 

Had we used a permitted pest control* such as plant derived insecticide (that's rapidly biodegradable) or a fatty acid spray that suffocates insects, we would have killed the pest's predators too, and have entered a cycle of needing to carry on applying control measures. Thank heavens we didn't.

*Sheepdrove Organic Farm is certified by the Soil Association. Their organic standards detail the methods that must be used for controlling pests and diseases including any permitted products. However the first method is to encourage natural predators within and around crops by doing things like companion planting, under-sowing and mixed cropping.

Find out more about natural pest control in organic gardening