What diseases affect geraniums?
Some of my geraniums have scale like spots on the underside of the leaves. The leaves turn yellow.
Certified GKH Gardening Expert
Your plants could have a pest issue or Virticillium can attack geraniums.
In the case of verticillium the plant would need to be disposed of.
Likely the plant just needs some watering adjustment and a Neem Oil treatment generally takes care of most insects or fungus.
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