Here is an article with advice: https://www.gardeningknowhow.com/ornamental/bulbs/dahlia/bugs-on-dahlia-plants.htm
HI Harper, this video might give you some ideas to try - https://www.youtube.com/watch?v=KIdjbLmKMng
You can spray a Mix of 2 to 4 tablespoons of concentrate neem oil with 1 gallon of water to control sap-sucking insects, such as aphids, thrips, spider mites and whiteflies. Cover all plant surfaces with the mixture until thoroughly wet.
ifyou have slugs/snails crawling up them, crush up some egg shells into small-ish pieces and put around the base of the plant.
or you can dissolve Epsom salt in water and spray it on and around the plant
Have you tried any soapy water?
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