Pest and Disease Management: Organic Solutions

Pests and diseases affect every allotment at some point. The aim isn’t total elimination, but understanding the problem, choosing the least harmful effective solution, and preventing repeat issues.

This guide explains what each control method actually is, how it works, how to use it properly, and when it makes sense to move up to stronger interventions.

🐌 SLUGS & SNAILS

The Problem

Slugs and snails feed mostly at night and are most damaging to:

• seedlings

• young leafy crops (lettuce, brassicas)

• courgettes and beans

Damage usually appears as irregular holes, missing seedlings, or slime trails.

Organic Solutions

Beer Traps

Beer traps exploit the fact that slugs are attracted to yeast.

How to make one:

1. Sink a shallow container (e.g. yogurt pot) into the soil so the rim is level with the surface

2. Fill halfway with beer (cheap beer works fine)

3. Leave overnight and empty regularly

Pros:

• Cheap and easy

• Effective short-term reduction

Cons:

• Attracts slugs from nearby areas

• Needs frequent emptying

• Not a complete solution

➡ Best used for monitoring or short-term control, not as a standalone strategy.

Barriers (Copper, Grit, Wool Pellets)

These create surfaces slugs dislike crossing.

• Copper tape gives slugs a mild electric shock reaction

• Sharp grit or crushed eggshells irritate their bodies

• Wool pellets swell when wet, creating a physical barrier

Best for:

• Containers

• Raised beds

• High-value crops

Hand Removal

Going out after dark with a torch and removing slugs manually.

Why it works:
You interrupt breeding cycles early in the season.

Tip:
Drop slugs into salty water or relocate far from the plot (if permitted).

Encouraging Predators

Natural slug predators include:

• frogs and toads

• ground beetles

• birds

How to encourage them:

• Leave log piles

• Avoid slug pellets

• Provide water sources

Non-Organic Solutions

Ferric Phosphate Pellets

These pellets cause slugs to stop feeding and die underground.

Why they’re preferred:

• Approved for organic use

• Safer for pets and wildlife

• No slime trails

How to use properly:

• Scatter sparingly

• Reapply after heavy rain

⚠️ Avoid metaldehyde pellets — now restricted or banned in many areas.

🐜 APHIDS (GREENFLY & BLACKFLY)

The Problem

Aphids suck sap from soft growth, weakening plants and spreading disease. They often appear suddenly in warm weather.

Organic Solutions

Jet of Water

A strong spray physically knocks aphids off plants.

Why it works:
Aphids struggle to climb back and are vulnerable once dislodged.

Use when:

• Infestation is light to moderate

• Plants are sturdy enough to handle water pressure

Neem Oil / Fatty Acid Sprays

These sprays:

• coat aphids

• disrupt feeding

• dehydrate soft-bodied insects

How to use:

• Spray in the evening

• Cover undersides of leaves

• Repeat weekly if needed

⚠️ Avoid spraying during flowering to protect pollinators.

Encouraging Beneficial Insects

Ladybirds, lacewings, and hoverfly larvae eat aphids.

How to attract them:

• Grow flowers like calendula, borage, alyssum

• Avoid broad-spectrum sprays

Non-Organic Solutions

Systemic Insecticides

These are absorbed by the plant and kill insects that feed on it.

Why they’re effective:
They work even when insects are hidden.

Major downsides:

• Kill pollinators

• Persist in the environment

• Often unnecessary on allotments

➡ Use only for severe, persistent infestations and check site rules.

🐦 BIRDS (PIGEONS & SMALL BIRDS)

The Problem

Birds strip leaves from brassicas, eat fruits and pull out seedlings.

Physical Protection (Best Practice)

Netting

Netting is the most reliable solution when used correctly.

Correct installation:

• Use fine mesh (not string netting)

• Secure edges tightly to the ground

• Support netting above plants with hoops or frames

⚠️ Loose netting can trap wildlife — always keep it taut.

Fleece

Lightweight fabric that:

• protects from birds

• adds warmth

• allows light and water through

Best for:

• seedlings

• early spring crops

🥕 CARROT FLY

The Problem

Adult flies lay eggs near carrots; larvae tunnel into roots.

Organic Solutions

Mesh Barriers

Carrot fly stays close to the ground.

Solution:

• Use fine mesh or fleece barriers at least 60cm high

• Ensure no gaps

Growing in Containers

Carrot fly struggles to reach raised containers.

Why it works:
Physical separation breaks the life cycle.

🍅 BLIGHT (POTATOES & TOMATOES)

The Problem

Blight is a fungal disease that spreads rapidly in warm, damp conditions.

Prevention (Only Real Control)

Good Airflow

• Space plants well

• Remove lower leaves

• Avoid overcrowding

Watering at Soil Level

Wet leaves encourage spores.

Best practice:

• Water in the morning

• Water soil, not foliage

Non-Organic Options

Fungicides can slow spread but cannot cure blight once established.

➡ Immediate removal of infected plants is usually more effective.

🍂 POWDERY MILDEW

The Problem

Appears as white powdery coating on leaves, often in dry conditions.

Organic Solutions

Improving Growing Conditions

Powdery mildew thrives on stressed plants.

Fix by:

• Regular watering

• Better spacing

• Improving soil fertility

Milk or Bicarbonate Sprays

These change leaf surface pH, making it hostile to mildew.

Use sparingly:
They manage symptoms rather than cure causes.

🛡️ PROTECTION STRATEGY: WHAT WORKS BEST?

Most effective overall:

1. Healthy soil

2. Correct spacing

3. Physical barriers

4. Observation and early action

Sprays — organic or not — should always be last, not first.

✅ KEY PRINCIPLES TO REMEMBER

• Most problems are seasonal and temporary

• Healthy plants resist pests better

• Physical protection beats chemical control

• Do the minimum needed, not the maximum possible

Get in touch if you have any other hints or tips from your allotment experiences