How to Prevent and Control Botrytis (Grey Mould) on Tomatoes, Strawberries, and Leafy Greens

One minute your strawberries are ripening beautifully, your tomatoes are flowering, and your lettuces are lush… and the next, they’re cloaked in a fuzzy grey menace. Botrytis cinerea, commonly known as grey mould, is a sneaky fungal disease that thrives in damp, still conditions and can decimate crops before you even realise it’s there.But fear not, there are simple, natural ways we can prevent and control botrytis and keep our crops thriving.

What Is Botrytis (Grey Mould)?

Botrytis is a fungal disease that affects a wide range of plants. It’s particularly fond of:

• Tomatoes (especially in greenhouses)
  
• Strawberries (when fruits are close to the soil)
  
• Leafy greens (lettuce, spinach, chard)

The fungus spreads through airborne spores and thrives in cool, humid, poorly ventilated environments. It typically shows up as:

• Fuzzy grey or brown mould on leaves, stems, or fruit
  
• Water-soaked lesions that quickly rot
  
• Brown, dying flowers that never form fruit

Once it gets going, botrytis can spread rapidly. Prevention is your best defence.

Prioritise Good Airflow

Grey mould loves still, moist air. Keep things breezy by:

• Spacing plants generously especially in greenhouses
  
• Pruning lower leaves on tomato plants to improve circulation
  
• Thinning dense leafy greens as they grow
  
• Using mesh sides or open vents in polytunnels and greenhouses

This helps moisture evaporate quickly and keeps fungal spores from settling.

Water Smart, Not Often

Overwatering creates the perfect damp environment for botrytis. Water:

• Early in the day so foliage dries before evening
  
• At the base of plants, avoiding leaves and stems
  
• With a soaker hose or watering can, never sprinklers

Avoid splashing soil or water onto fruits, especially with strawberries and lettuce.

Mulch and Elevate Fruit

Protect vulnerable fruit by keeping it off the soil:

• For strawberries, use straw mulch or fruit rings to lift berries above damp ground
  
• For leafy greens, mulch with well-rotted compost to reduce splashback
  
• For tomatoes, remove any lower fruit trusses that sit near the soil

This prevents botrytis spores from splashing up onto tender fruit.

Remove Infected Material Immediately

The moment you spot mould, act fast:

• Cut off affected leaves, stems, or fruit and dispose of them (don’t compost!)
  
• Clean pruners with vinegar or rubbing alcohol between plants
  
• Check regularly during cool, damp spells, daily if needed

Leaving infected material on the plant or ground gives botrytis a green light to spread.

Avoid Overfeeding with Nitrogen

Too much nitrogen leads to soft, leafy growth that’s more prone to infection. Balance your feeding with:

• A low-nitrogen, high-potassium feed for fruiting crops like tomatoes and strawberries
  
• A general-purpose organic feed for leafy greens once they’re established

Strong, balanced growth is far less inviting to disease.

Try Natural Preventatives

While we avoid chemical fungicides, there are a few organic tools in the kit:

• Garlic spray: A natural antifungal made from crushed garlic steeped in water
  
• Milk spray: 1 part milk to 9 parts water, misted on leaves to inhibit fungal spores
  
• Compost tea: Boosts beneficial microbes that can outcompete grey mould

Apply weekly in damp conditions or as a preventative measure.

Rotate and Rest Beds

Botrytis spores can overwinter on plant debris and in soil. We help break the cycle by:

• Rotating crops every year, especially tomatoes and leafy greens
  
• Removing all plant debris at the end of the season
  
• Solarising soil in the greenhouse (covering with clear plastic in summer) to kill pathogens

Good hygiene is your garden’s first line of defence.

Good hygiene is your garden’s first line of defence.

Grey mould may be common, but it doesn’t have to claim your crops. With some airflow, smart watering, and vigilant pruning, you can prevent and control botrytis naturally. Your tomatoes will ripen on the vine, your strawberries will stay plump and clean, and your leafy greens will stay fresh and fungus-free.