My dragon wing begonias have curling leaves---not all
Ramsey County Minnesota
Begonias do not like wet feet, so make sure your planter is well draining.
Do you see any discoloration or spots on the leaves?
Tan spots on leaves and plant rot at the base are result of fungal disease (Botrytis).
Treatment: This disease is common with rooted cuttings and is best prevented by using a clean, pathogen-free medium. Discard affected plants and start new plants form clean stem tip cuttings.
Spots with yellow halos on the leaves are results of bacterial leaf spot.
Treatment: Remove affected leaves and increase air circulation. Discard infected winter blooming as they carry these disease throughout their system.
Mildew is not the problem with Begonia coccinea that it can be with other begonias, but fungal disorders can certainly set in if plants are too crowded, watered from overhead or have poor air circulation.
Watch out for mealybugs and aphids on foliage.
Treatment: Control them by dabbing with alcohol-soaked cotton swabs. Repeat the treatment every 5 days until the problem is solved. Do not use oil sprays to control pests on any begonias.