As shown in the photo, dahlias attract insects, some of which are harmful to the dahlia. Dahlias are also subject to several diseases which are described below.
Problems with Flowers
- Flowers & / or buds shrivelled and with fluffy white mould = Botrytis.
- Flowers with mass of mites covering bloom (Generally seen when bloom brought into the house for decoration purposes) = Red Spider
- Flowers with tattered petals = Earwigs
- Flowers with light flecking on petals, many small long-bodied winged and wingless insects present = Thrips
- Flowers with irregular holes and pieces eaten away and slime trail present = Slugs and Snails
- Flowers with holes (centre of bloom) and petals with pieces eaten away; no slime trails present on or near flower = Caterpillars
Problems with Foliage
- Leaves with numerous pale spots = Smut
- Leaves with white dust like covering = Powdery Mildew
- Leaves variously crumpled with irregular, pale yellowish patterns with insects visible more so with a magnifying glass = Red Spider
- Leaves variously crumpled with irregular, pale yellowish patterns with no insects visible with a magnifying glass = Virus
- Leaves wilt; stem interior with brown or black streaks = Wilt
- Leaves with irregular holes and pieces eaten away with slime trails present on or near plants = Slugs and Snails
- Leaves with irregular holes and pieces eaten away; no slime trails present on or near plants = Caterpillars
- Leaves with small tattered holes, especially at tips of shoots; buds sometimes killed = Capsid Bugs
- Leaves, shoots and flowers infested by colonies of black, green or yellow wingless and winged insects; Foliage sticky and sometimes sooty = Aphids
- Stem with soft, irregular swelling = Crown Gall
- Stem base rotted, cottony white mould growth present = Sclerotinia Disease
Virus attack
The plants in the background are of the same cultivar
Crown Gall
Picture illustrating Crown Gall, here on a stored tuber although the tuber showed no physical signs until it began to shoot
Red Spider
Severe Red Spider
