Botrytis (Grey Mould) on Pansies and Violas: What to Do

Botrytis cinerea, known as grey mould, is one of the most destructive fungal diseases affecting pansies and violas in the UK and northern Europe. It thrives in exactly the conditions that cool-season pansies need — cool, damp weather with limited air movement — which makes it a persistent challenge. A grey, fuzzy coating over dead flowers, leaves, and stems is the unmistakeable sign, and the spores spread from plant to plant with remarkable speed if conditions remain damp.

Identifying Botrytis on Pansies

Botrytis infection almost always begins on dead or dying plant material — spent flowers that have not been removed, damaged leaves, or soft growing tips damaged by cold. The grey, powdery mould appears first on these weak spots and then spreads to adjacent healthy tissue. Infected stems may collapse at the point of infection, and the characteristic cloud of grey spores puffs out when the infected material is disturbed. In severe cases, entire plants can be engulfed within a week of the first symptoms appearing in cool, wet autumn or spring weather.

Remove Infected Material Immediately

As soon as you spot botrytis, act fast. Put on gloves and carefully remove all infected flowers, leaves, and stems, working slowly to avoid releasing spore clouds. Place removed material directly into a sealed bag and dispose of it in general waste — do not compost it, as botrytis spores survive composting and will reinfect your garden. After removing all visible infection, wash your hands and tools thoroughly before touching other plants.

Improve Air Circulation to Stop the Spread

Botrytis cannot establish easily in well-ventilated conditions. Thin out dense plantings to allow air to move freely between plants. If you are growing in a greenhouse or polytunnel, increase ventilation by opening vents and doors during the day. Avoid overhead watering — water at the base of plants in the morning so foliage dries quickly. Space containers further apart if plants are crowded on a patio or bench.

Deadhead Religiously to Remove Entry Points

Dead and dying flowers are the primary entry point for botrytis. Remove every spent flower at least every two to three days, particularly during cool, damp weather. Do not leave old petals lying on the compost surface where they provide a germination point for spores. This single cultural practice dramatically reduces botrytis pressure throughout the season without any chemical input.

Fungicide Treatment for Severe Infections

If botrytis has spread extensively despite cultural controls, a fungicide based on potassium bicarbonate or copper can help slow the spread. Follow label instructions carefully and apply in the evening to avoid harming pollinating insects. Rotate products if applying more than twice, as botrytis develops resistance to fungicides quickly. Do not rely on fungicide alone — cultural controls must accompany any chemical programme.