Dahlias - Ask Extension
Hello! I recently purchased several different flowering plants from a local greenhouse about 2 weeks ago. I am having issues with almost all of them i...
Knowledgebase
Dahlias #868782
Asked May 16, 2024, 6:06 PM EDT
Hello! I recently purchased several different flowering plants from a local greenhouse about 2 weeks ago. I am having issues with almost all of them including a mandevilla, dahlias, lantana, and bracteantha. I’m not sure if they are all related or not.
The dahlias have holes in both the leaves and the flowers. The leaves on the inside of the plant are being eaten. There appears to be a white sandy substance on the inside of the plant.
Kalamazoo County Michigan
Expert Response
Thank you Melany for your question!
The holes in your dahlia leaves may be from spider mites as well as slugs/snails. These articles explain in depth what they are and how they can be controlled.
Twospotted spider mites in home gardens | UMN Extension
Slugs in home gardens | UMN Extension
Examine the underside of the leaves for evidence of spider mites. Consider applying a horticultural oil or insecticidal soap for spider mite control as chemical reagents can impact natural predator mites.
Slugs can be handpicked or baited with various kinds of traps.
Cut back affected foliage and use a soaker hose to water your dahlias, not overhead watering.
Be vigilant in your dahlia monitoring for other signs of disease. Refer to the following articles for further instructions.
Pests & Diseases - National Dahlia Society (dahlia-nds.co.uk)
Dahlia Diseases (psu.edu)
Happy Gardening!
The holes in your dahlia leaves may be from spider mites as well as slugs/snails. These articles explain in depth what they are and how they can be controlled.
Twospotted spider mites in home gardens | UMN Extension
Slugs in home gardens | UMN Extension
Examine the underside of the leaves for evidence of spider mites. Consider applying a horticultural oil or insecticidal soap for spider mite control as chemical reagents can impact natural predator mites.
Slugs can be handpicked or baited with various kinds of traps.
Cut back affected foliage and use a soaker hose to water your dahlias, not overhead watering.
Be vigilant in your dahlia monitoring for other signs of disease. Refer to the following articles for further instructions.
Pests & Diseases - National Dahlia Society (dahlia-nds.co.uk)
Dahlia Diseases (psu.edu)
Happy Gardening!
