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Q.  My citrus trees although fully laden with fruit, are suffering from a bad infestation of fungus and lichen.  Is it okay to spray them now?  - Mrs E. Marsden, Wellington.

Geoff Willsher replies:  No.  Spraying with Yates Copperoxichloride will get rid of the fungus, but will also temporarily defoliate the trees.  I recommend you spray after harvesting. As for the lichen, LICHEN doesn’t do the tree any harm. It’s actually a good sign, as lichen needs clean air to survive. In parts of the world where pollution is bad, lichens are becoming rare.

Lichens are two organisms living in symbiosis – a fungus shelters an alga which provides food for the fungus. Vigorously growing trees shed bark regularly, which tends to limit lichen growth, so it’s also a sign your apple tree isn’t growing very strongly. I suggest you feed the tree to encourage more growth and, if you do wish to remove some of the lichen, simply try brushing it off. If you want to deal to it on a larger scale, spray with lime sulphur in winter when the tree is dormant, or paint the spray solution on to the lichen. Lime sulphur is nasty stuff though and should be handled with care. My best is advice is that you learn to live with your lichen.