Something is eating my Dahlia foliage. I cannot catch it to describe what it is. It is some sort of insect or bug I guess.
Can I spray the plant with a soap and water solution? Are there other treatments for the Dahlia plant?
Benita Ann Gallina
From your description, the most likely culprits are snails or slugs. They chew irregular holes in and around the edges of leaves, and are active at night. Earwigs, which anecdotally are very plentiful this year, are also attracted to Dahlias, and can damage foliage, flowers and buds.
The Toronto Master Gardeners do not recommend home remedies such as soap and water, which can damage the foliage of plants and is not formulated to deter insect pests. Commercial insecticidal sprays (which are formulated for this purpose) are not effective against slugs. There are commercial products specifically formulated to deter slugs and snails that do not harm foliage or beneficial insects – you can look for these in nurseries and garden centres. Hand-picking slugs and snails towards dusk when they are actively feeding is also effective. Here is a previous Toronto Master Gardeners post which contains useful information about control of these garden pests: https://www.torontomastergardeners.ca/askagardener/how-can-i-get-rid-of-slugs/
To minimize damage by slugs, snails and earwigs, make sure the soil at the base of your Dahlias is kept clear of leaves and other materials, and if you are using leaves as mulch, consider removing it as it is a habitat for earwigs. You might also clip off the bottom few inches of your Dahlia foliage in order to increase air circulation and provide an environment which is less moist and cool, and therefore less welcome to these pests.
July 4, 2021