Leaf Spot on Pansies and Violas: What Is Causing Those Brown Spots?

Circular or irregular brown, tan, or black spots on pansy and viola leaves are caused by fungal leaf spot diseases, most commonly Ramularia species and Colletotrichum (anthracnose). Both are encouraged by wet weather, overhead watering, and dense planting that keeps foliage damp for extended periods. While leaf spot is rarely fatal to established plants, a severe infection defoliates them and reduces flowering significantly.

Identifying the Different Leaf Spot Diseases

Ramularia leaf spot produces small, roughly circular spots that are tan or pale brown in the centre with a purple-brown border. As infection progresses, spots enlarge and may merge, giving leaves a blotchy, browned appearance. A faint white mould can sometimes be seen in the centre of older spots in humid conditions. Anthracnose produces darker, more irregular spots that may have sunken centres and orange or pink spore masses at the centre in wet weather. Both types of spots begin on the lower, older leaves and move upward with time.

Removing Infected Leaves Halts the Cycle

Fungal leaf spot spreads by releasing spores from existing lesions, particularly when leaves are wet. Removing infected leaves as soon as they are spotted — and bagging them rather than dropping them on the soil — physically removes a significant proportion of the spore load and slows the spread to healthy tissue. Remove leaves cleanly at the stem with a sharp, clean tool. Wash your hands after handling infected material to avoid spreading spores to other plants.

Cultural Controls Are the First Defence

Reduce leaf wetness duration to deprive the fungal spores of the moisture they need to germinate. Water at the base of plants in the morning rather than overhead in the evening. Space plants at least 20–25 cm apart so air can move between them and leaves dry quickly after rain or dew. Remove any dead leaves or plant debris from the soil surface around affected plants, as spores overwinter in dead material and reinfect plants the following season.

Fungicide Application for Persistent Infections

In seasons with persistent wet weather, cultural controls alone may not be enough to prevent leaf spot from spreading. A copper-based fungicide applied to both upper and lower leaf surfaces provides a protective barrier. Apply before wet weather if possible, and reapply after heavy rain. For anthracnose specifically, a fungicide containing thiophanate-methyl or myclobutanil (where approved for ornamental use in your region) provides better systemic control. Always follow label directions and note any pre-harvest intervals or pollinator restrictions.

Improving Plant Vigour Reduces Susceptibility

Healthy, well-fed, well-drained plants resist leaf spot infection more effectively than stressed plants. Ensure adequate drainage, feed regularly with a balanced fertiliser, and remove stressed or damaged tissue promptly. Avoid working among plants when foliage is wet, as this spreads spores on hands and clothing. After a severe outbreak, replace the top layer of compost in containers before the next planting season to remove overwintering spores.