Your dahlia is clearly not doing well. Its growth is stunted and the leaves are blotchy and twisted. You’re wondering if it’s missing some type of nutrient, but nothing seems to help. Sadly, you may be witnessing mosaic virus in dahlias.
Dahlia Mosaic Symptoms
Mosaic virus in dahlias cause large scale disfigurement of the plant. It is found worldwide and is spread by inoculation of the sap, either through human intervention or by the 13 species of aphids that serve as its natural vectors.
Dahlias with mosaic virus can exhibit a multitude of symptoms. The severity and type of dahlia mosaic symptoms can depend upon the particular variety or cultivar:
- Chlorophyll loss resulting in light-colored, pale green to yellow streaks along the branch veins and midveins of the leaves.
- Distortion of leaf growth resulting in stunted, twisty, rolled or cupped leaves
- Short flower stems with reduced number of flowers and small blossoms
- Necrotic black spotting on the leaves, often near the midvein
- Stunted growth of entire plant, poor root (tuber) development
Dahlia Mosaic Control
Once a dahlia has been infected with the virus, it enters the plant’s cells and begins multiplying. This makes treating dahlia mosaic infected plants impossible. To prevent spread of the virus, it’s best to remove dahlias with mosaic virus.
Fortunately, Dahlias with the mosaic virus can’t directly infect other dahlia plants. The virus is only spread by sap from an infected dahlia to a wound or opening in an uninfected one. Following these tips can help prevent the spread of the virus and offer the best method for dahlia mosaic control:
- Control aphids on dahlias and neighboring plants. When these tiny insects penetrate the dahlia’s epithelium, they ingest the mosaic virus along with their meal of sap. As they move from plant to plant, the virus is spread to uninfected dahlia plants. Adopting a spray program to eliminate aphids is effective. Organic growers can use insecticidal soaps.
- Don’t divide or propagate dahlias with the mosaic virus. The virus is present in both the tubers and stem cuttings. The dahlias grown from these methods of propagation will carry the virus and exhibit dahlia mosaic symptoms.
- Disinfect tools and wash hands after handling diseased plants. When removing dead leaves, pruning stems, dividing tubers or cutting flowers on dahlias, be sure to practice proper sanitation. The virus is transmitted by infected sap which can reside on cutting blades. Disinfect tools with a bleach solution. In lieu of frequent hand washing, use disposable gloves and change them often.