Why Is Grey Mould Spreading Across My Pea Plants?

A grey, fuzzy, cloud-like mould developing on pea stems, leaves, flowers, and pods — spreading rapidly in damp, cool weather — is Botrytis cinerea, the grey mould fungus. Botrytis is an opportunistic pathogen that attacks damaged, dying, or senescent plant tissue first and then spreads into healthy growth. In peas, it most commonly attacks collapsed or wet foliage lying on the soil, dead flower petals trapped between developing pods, and any damaged stem tissue. Dense plantings in wet weather are the highest-risk situation.

How botrytis establishes

Botrytis spores are omnipresent in garden air and can infect any plant tissue, but they need moisture and a compromised entry point to establish. Dead or dying tissue — spent flowers, yellowing lower leaves, storm-damaged stems — is the typical entry point. Once established in soft, wet tissue, the fungus produces enormous quantities of grey spores (conidia) that spread by air movement and water splash to nearby healthy tissue. In dense plantings where the canopy is wet for extended periods, Botrytis can spread through an entire row within days during prolonged damp weather.

Removing infected material

Cut out and bin (do not compost) any visibly mouldy tissue as soon as you see it. Use clean, sharp tools and work in dry weather if possible — handling infected plants in wet conditions distributes spores to healthy tissue. Removing dead flower petals from between developing pods is particularly important, as these are a primary infection point. Lower leaves that are yellowing and dying off naturally (which happens progressively as the plant ages) should be removed before they collapse and create damp zones at the base of the plant.

Cultural prevention

Sow peas at the correct spacing for the variety — typically 5–8 cm between plants in a row, with rows 45–60 cm apart for tall varieties. Overcrowding prevents air movement, keeps foliage wet longer after rain or dew, and creates ideal botrytis conditions. Support peas properly so foliage stays off the soil. Avoid overhead watering, especially in the evening. In a wet season, botrytis pressure can be severe regardless of management — the only mitigation is consistent removal of dead tissue and acceptance that some pods may be affected at the end of the season.