Answer: Curling, lumpy leaves are generally attributed to a pest problem. Look closely at the affected leaves, with a magnifying glass, if possible. You'll probably find tiny spider mites on the undersides of the leaves. These pests suck the juices out of plant tissue and leave bumps in return. Spider mites like dry conditions, so mist the leaves of your plant to increase humidity. They're not really insects, so insecticides aren't especially helpful in their control. You can use horticultural oil to smother the pests and their eggs (read and follow label directions), or you can wash them off with plain water (repeat as often as necessary). Increasing the humidity around your citrus tree will help prevent future infestations.
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