Plant Doctor Archive

Borer in my mandarin tree

I have spent a lot of time and expense on this tree as the leaves were yellow, and have taken all sorts of advice. However, two branches of the tree went dead and we cut them off and found a hole right through the branch as if something was eating it through the bark. Can you advise as to what this is?

This is likely to be lemon tree borer, which does not, as its name suggests, confine itself solely to lemon trees. Satsuma mandarin trees, for example are very susceptible to lemon tree borer. You will need to remove the infested branches and burn them or put them in the rubbish because the larvae will continue to live in the dead wood.

The cut ends will also need 'painting' to prevent reinfestation. If you cut the branches of your citrus tree in the warmer months, the adult beetle will lay its new eggs on the cutting wound. For this reason pruning should normally be restricted to the winter months when adult borer flight is minimal. If you do make a cut in summer, dress the wound with a pruning paste.

The following article explains the life cycle of the pest and how to treat it:

Lemon tree borer and how to get rid of it

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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