The case of the black moss

A couple of years back I planted a fever tree outside our gate.  The tree never really took off.  It didn’t die or look sickly, it just never seemed to grow.  I put it down to the fact that the soil I had planted it in was this terrible, sandy, red earth and decided to give it some time to come right.

However, earlier this year, I noticed a black moss growing on the trunk and branches of the tree and thought I better do something about it.  First I Googled black moss but didn’t come up with anything useful.  Then I went to take a closer look at the tree and noticed hundreds of small, black ants moving up and down the tree trunk.  Could the ‘black moss’ actually be the ants footprints, I wondered?

After a bit more Googling, I found something that surprised me.  Both the ants and black moss were indicator species, pointing to the real culprit, aphids.  I went back to inspect the tree for a third time and lo and behold, there in the leaves, were hundreds of tiny aphids.

So, in pulling all the pieces of the puzzle together, I worked out that the ants were protecting and ‘milking’ the aphids for their carbohydrate rich excrement, called honeydew.  This was also coating the trunk and branches of the tree, providing a perfect environment for the black moss to grow.

Solution, kill the ants and let the aphids natural predators control the population.

Result, the fever tree has suddenly sprung to life.

New leaves sprouting on the fever tree.

New leaves sprouting on the fever tree.

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10 Responses to The case of the black moss

  1. emme March 25, 2009 at 11:27 am #

    cool story!

  2. Niall McNulty March 25, 2009 at 11:30 am #

    thanks em, I did feel pretty satisfied with myself after working it all out 🙂

  3. Ross March 25, 2009 at 2:00 pm #

    Hey Niall, this is also usually a sign that the soil is not great, which puts the poor tree under a bit of stress, and so it becomes more prone to pests and diseases. If you dig in some compost around the base and give it plenty water – the aphids won’t come back.
    Uncle Google is one of my best friends too…

  4. Niall McNulty March 25, 2009 at 2:07 pm #

    so the soil was also to blame after all. thanks for the tip Ross …

  5. emme March 26, 2009 at 11:03 am #

    i’ll never feel the same way about honeydew yoghurt.

  6. brendan March 26, 2009 at 2:52 pm #

    good investigation watson

  7. Sarah L March 27, 2009 at 6:39 am #

    Fever trees also take a long time to establish a root system to support them when they grow tall.

    My dad planted one in our front garden and for years it remained healthy but leetle. Then, almost overnight, it shot up and is now big and beautiful 🙂

    My dad always had faith that it would reach its potential – an essential element of gardening I would think…

  8. Niall McNulty March 28, 2009 at 7:04 am #

    hi sarah. that is good news. hopefully this is the year that it shoots up.

    faith and patience is indeed a virtue when it comes to gardens …

  9. Coetzee January 16, 2010 at 2:26 pm #

    Also found the same regarding aphids on fever trees.

    What is the best fertilizer to use on fever trees?

  10. Niall January 16, 2010 at 7:42 pm #

    Hey Coetzee. I used a green manure made from comfrey which worked very well.

    See http://www.sprig.co.za/2009/07/green-tea/ for the recipe.

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