Hollyhock Rust

• Hollyhock rust is a fungal disease that causes yellowing of hollyhock leaves and premature leaf drop. The first symptom is small blisters that grow underside of low-lying leaves. The blisters cause discoloration and damage to the surface of leaves. Remove infected leaves. If rust returns, apply specific kinds of fungicide.
  
  

Iron Chlorosis

• Iron chlorosis is nutrient imbalance that causes hollyhock leaves to turn yellow. The tell-tale sign of iron chlorosis is that the leaf's veins remain green while the rest of it turns yellow. To treat iron chlorosis, spray your hollyhock plant with a prescribed iron compound.
  
  

Hollyhock Weevils

• Hollyhock weevils are pests that feed on hollyhock leaves, which results in yellowing leaves, leaf damage and defoliation. Weevils are inactive during the day, so shaking the plant can remove them (just have a towel laid out to catch these pests). Additionally, certain pesticides also destroy hollyhock weevils.