Dahlia
Symptom Cause  
Leaves wrinkled or curled; discolored, stunted, tend to fall off
Aphids
>
Buds discolored; tunnels in stems; plants wilted
Borers
>
Tops eaten to ground; hoof prints nearby
Deer
>
Plants wilt; stem, leaf discoloration; plant dies
Fusarium Wilt
>
Plants don't bloom in summer
Hot Weather
>
Tip of leaves brown, internal larvae trails visible. Leaves skeletonized and rolled up.
Leaf Miners
>
Leaves discolored; distorted; growth stunted
Leafhoppers
>
Leaves discolored and deformed; webbing present
Mite
>
Plants stunted; yellowed; root lesions
Nematodes
>
Lush foliage; sparse bloom
Over Fertilized
>
Bulbs eaten, plant might have been pulled underground
Pocket Gophers
>
Leaves covered with white powder
Powdery Mildew
>
Ragged holes in leaves, often in middle
Slugs and Snails
>
Black powdery sooty mold fungus forms on honeydew; plants may die
Sooty Mold
>
Leaves turn yellow and wilt
Stem Rot
>
Leaves stippled/yellow/bronze/dry Drop. Black feces near affected plant tissue
Thrips
>