Lemon trees will often get little bumps and blisters on their leaves. This is most likely caused by tiny insects called gall makers. The appearance of these insects, Tryoza erytreal, is a common problem in citrus trees.

Linda B asks:

I have a lemon tree and a small lime tree in a pot and I need to know what I should feed them with.  Also, my lemon tree has leaves that have curled up with many bumps on them – I’m sure this is a disease – how do I cope with this organically?

Your citrus trees require the macronutrient magnesium. The lack of magnesium in South African soil  can be compensated for by adding some Epsom salts (magnesium sulphate) to the base of the tree. Sprinkle a couple of handfuls per plant and water it in.

The question about whether this is an organic treatment is open for debate – although since there is a natural lack of magnesium in South African soil it is unlikely that the required quantities of magnesium will occur naturally or be produced naturally (by earthworms for example).  Epsom salts won’t harm the environment and is safe to humans and animals in moderate quantities. Adding Epsom salts to a warm bath is also a known remedy for eczema.

To treat the bumps and blisters on the leaves of your lemon tree you can try Natural Rape Oil Insecticide, which is a natural insecticide concentrate for the control of infestations of psylla often used on roses and other ornamental plants.

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