Dealing with popular pests

Slugs and aphids are every gardener’s worst nightmare and can ruin the best-laid growing plans – this month’s GYO column reveals how to deal with them the organic way.

I’ve called this month’s column ‘popular pests’ – not because you want to invite them to your garden party, but because this is the time of year they make themselves busy. And the two top of the pops are aphids and our old friends the slugs.  

So before we look at each one, I first want to share with you the organic approach to dealing with pests. As you’ve probably guessed, it doesn’t involve reaching for the bright red bottle of toxic bug spray.

Instead, the canny organic grower will work on the principle of prevention. Here’s how:

  • Keeping your soil healthy and full of life. If your plants are well nourished, it helps them withstand the onslaught of most pests. So put plenty of home-made compost into the soil to feed the important soil micro-organisms, and it’ll add slow release nutrients to boost your plants. 
  • Encourage those helpful pest predators. Watching nature work in your growing area is fascinating. Aphids and caterpillars will hatch in perfect time for birds and insect larvae who feed on them. You can work with nature by creating a diversity of plant life which in turn will attract a huge mix of beneficial wildlife. Plant flowers with your veg to bring in a variety of aphid munching insects; put in shrubs for birds to shelter in; and leave grass long to provide insect and small mammal habitat.
  • Choose plants and varieties that are suited to the site and soil. Plants which struggle to grow will be weak and vulnerable to pest and disease. Similarly, if you have seedlings, give them a chance to mature before planting them out.  They will have less soft green growth which is so attractive for pests to eat.
  • Use traps, barriers and covers to keep those hungry slugs, caterpillars and pigeons at bay. And be vigilant! Keep checking your defences. Especially after rain or in damp conditions, when dry slug deterrent material will have become moist.

Now, here’s is a quick check list on how to deal with your dastardly duo, and for more, go to Garden Organic 


Often known as greenfly or blackfly, they cluster around tender young growth, sucking out the sap and causing young shoots to become weak and distorted. A simple way to prevent them is to avoid using too much nitrogen-rich fertiliser which encourages soft leafy growth. 

Then you have a number of options to keep on top of them. Encourage creatures that eat aphids (such as birds, earwigs and bats) by providing them with habitat and food. Grow flowers like fennel, cow parsley and the daisy family which attract hoverflies, lacewings and ladybirds – these insects and their larvae feed on aphids. Finally, you can squash any you see (wear gloves if you’re squeamish) or use a strong jet of water to dislodge them.

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Encourage plants that attract insects like ladybugs that then feed on aphids. 

It’s important not to panic when you see aphids. You need to be patient and wait for the predator. After all, if we wipe out the aphid population, we also threaten the ladybirds’ and songbirds’ survival.


Slugs love rich, damp conditions – which means organic growers can suffer particularly unfairly as they provide compost mulches which are slug heaven. 

Tempted by slug pellets? Think again First of all, never buy ones with the deadly poison metaldehyde in them. The pellets certified for organic use ferric phosphate which degrades harmlessly into the soil  however, other chemical ingredients in the pellet may cause problems to soil life. So use them very sparingly. 

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Be very wary of using pellets to solve any slug related woes, even the organic ones. 

Whatever your way of dealing with pests, don’t ever be tempted by the toxic poisons which are so freely available on garden centre shelves. They kill not only the pest but other species as well. If you spray an aphid, the chances are you will kill a friendly hoverfly; if you poison a slug you might poison the toad who eats that very slug. Just let nature deal with your popular pests.

The Grow Your Own Wicked Leeks series is written by Garden Organic, the national charity for organic growing. Each month we bring you timely advice on what to do in your organic patch, whether you’re an experienced grower or just starting out. Share your own tips and gardening photos on social media under #GYOWickedLeeks.


Leave a Reply

    1. Thanks James, for picking me up on my word usage. It’s always helpful.
      I guess I used popular, not in the sense of liked by many, but with the meaning of understood by many. There are a lot of obscure plant pests and diseases known only to scientists and horticulturalists, but the ones I chose to mention above will probably be well known by nearly all gardeners and growers.
      And you’re right, they certainly aren’t liked by us!

    1. Good question. A barrier can be either physical or a sensory repellent. There are many types, either home-made or bought products are available:
      Bottle cloches – cut the bottom off a clear plastic bottle and firm it into the soil around a vulnerable seedling/plant.
      Slug collars – plastic rings with a lip to make crossing it difficult, placed around individual plants such as lettuce.
      Grit or Granules – natural mineral products that either form a sharp, gritty repellent barrier or that suck the moisture from the slime that slugs and snails exude as they move.
      Spray repellent – made from yucca plant extract, spray on to surfaces and around vulnerable plants. Especially useful in hard-to-protect-places like greenhouse window frames. Needs renewing after heavy rain.
      Copper tape/rings and impregnated mats – copper gives a natural electric charge that repels these pests. Tape is useful around pots and legs of greenhouse staging, mats may be used around plants or planted through.
      Bran – slugs like to eat the bran, it swells inside them, reducing their appetite for your precious plants.

  1. What is your opinion on this product please? “Envii Feed & Fortify is an innovative organic slug control method that offers several benefits compared to traditional methods. Made using diatomaceous earth, Envii Feed & Fortify is a dual purpose, organic treatment that both protects and feeds your plants. The unique properties of diatomaceous earth allow it to create an impenetrable, physical barrier around your plants. The iron silicates improve soil fertility and increase a plants ability to take more nutrients on board.”
    Years ago when we rescued some chickens, I used to use diatomaceous earth in their chicken shed after I had cleaned it out – but it did say on the box DON’T BREATHE IT IN as it can damage your lungs!
    I could not see any warning with this product but I assume it too could damage your lungs if not careful to not breath it in?
    Also, as far as other insects are concerned, “it will dry and desicate their waxy bodies” – so would this be good to use or would it cause too much damage to other good insects?
    I have just started to use this one, Envii Feed & Protect which seems to be working at least a little so far.

  2. You make a good point about being careful to avoid any off-target effects from any product that you might use. Certainly the action of desiccation will affect ground beetles and other soil insects.


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