That's not the ants that are damaging them. Ants farm aphids for their honeydew excretions, so that's what they might be doing. Aphids suck the sap from plants and they are more likely to cause some damage, although it's unlikely they could damage a stem to that extent. If you have a lot of ants around your dahlias, it suggests they're very dry. Dahlias need a lot of moisture and sun to grow well, so it sounds like they're very dry at their base. Slugs may eat stems as they come through, but it wouldn't affect a mature healthy plant - it will shrug off attacks from molluscs. Do you have a photo?
It's a place where beautiful isn't enough of a word....
I live in west central Scotland - not where that photo is...
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If you have a lot of ants around your dahlias, it suggests they're very dry. Dahlias need a lot of moisture and sun to grow well, so it sounds like they're very dry at their base.
Slugs may eat stems as they come through, but it wouldn't affect a mature healthy plant - it will shrug off attacks from molluscs.
Do you have a photo?
I live in west central Scotland - not where that photo is...
I live in west central Scotland - not where that photo is...