Answer: Cool, humid springtime weather can encourage rust on snapdragons, as can water on the leaves for extended periods of time. Generally the plants become stunted and die and by the time we notice the infection, the plants are fully involved. You can try using sulfur based fungicides or Neem oil, but it's sometimes best just to pull the infected plants and destroy them. There are disease resistant varieties of snapdragons. You may want to plant those in your garden next year.
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