Answer: Border dahlias usually develop tubers which you can dig and save for replanting next year so the plants you have that are growing okay now should reward you with a little tuber or two after frost nips the tops of the plants. Be sure to wait until then and dig around beneath the plant to see if there are any tubers attached to the main stem. If so, brush off the dirt and store them in a cool but above freezing area until next spring. You can replant them and have new plants.
Lots of bugs munch on dahlias but not all bug sprays are effective against all kinds of bugs and dahlias can be sensitive to bug sprays so I would not spray to control bugs until you can identify the pest. When you do, look for a garden spray that is effective against them but safe for use on dahlias. Best wishes with your dahlias.
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