Organic Pest & Disease Control

Speaker: Lucy Frost
28th March

2. Lucy Frost

Lucy chatting to Chairman Liam while the audience reads her handout


First of all Lucy recommended her “Bible” The Complete Manual of Organic Gardening and then launched into her Power Point presentation. Part I was about disease control and Part II was on pest control. She also gave us a handout on methods of slug control ref. “101 ways to a slug free garden” (Organic Gardening Magazine, April 2003) and which suggested some rose and potato varieties with good disease resistance.

Part I

Stressed the importance of recognising and diagnosing the problem e.g. too much water, light, nutrients etc. and treating the symptoms which might include plant death (whole or part); spots; wilt; leaf fall; fungus.

The most common problems include:

  • Blight – potato, use Bordeaux mixture and choose a resistant variety like Sarpo Axona or Pink Fir Apple – tomato, remove all leaves when you spot it and burn them
  • Canker – affects many plants, choose varieties carefully
  • Club root – grow your brassicas from seed and don’t buy in or accept plants from friends.
  • Leaf curl – on peaches and nectarines, caused by rain on blossom
  • Grey mould – (Botrytis) towards the end of summer in the greenhouse when its damp and cool. To prevent handle seedlings by their leaves with care
  • Spots – back spot on roses, remove affected leaves and burn. Choose disease resistant varieties, grass cuttings around plants keep the spores down.

Rotate crops to help solve the problems:


O – Onion family

B&P – Beans & Peas

C – Cabbage

R&P – Root Crops & Potatoes

Also avoid monoculture, mix vegetables, flowers and herbs together in the potager. Choose disease resistant varieties and use organic fungicides where possible and sterilise soil where practical.

Part II

Spot the Slug

Spot the Slug

Required us to be inventive in our control of mammals, birds and invertebrates.
Spot the slug!

Lucy had many solutions to offer including the following, have a balanced ecology and attract natural predators like hedgehogs, hover flies, ladybirds, lacewings & their larvae, ground beetles, frogs & toads, thrush, shrew & field vole. Have a pond (can be tiny) for wild life.
Use companion plantings in the vegetable patch, sweet corn with marrows, French marigolds with tomatoes, carrots & onions. Also have borders of flowers and vegetables, and then the vegetables don’t provide such an easy target and the flowers attract insects.

Try biological methods, nematodes and tiger slugs for slug killers. Pheromones and traps for codling moth in fruit trees, pathogens for caterpillars on cabbages, parasitic wasps in the greenhouse. A slug pub, i.e. a vessel sunk in the ground full of beer will attract the slugs but also ground beetles. Ensure the edge of the vessel is above the ground so the beetles can’t fall in. Use physical barriers, grit, carpet underlay, solar bells or plastic bottles, cages, porous black plastic, and enviromesh. Use dangling bird scarers e.g. using a CD (Compact Disc).

Organic sprays, pyrethrum, soap sprays and as a last resort remove the pests by hand. Some of the worst pests are soil based e.g. wire worms and cut worms, aphids and caterpillars are old enemies.

In summary Lucy emphasised that hygiene is essential, use a many pronged attack, be vigilant and inventive, use natural predators and mixed planting but sometimes tolerance is a virtue.

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