Tuesday, 26 April 2016

Pine Die-back in Crete, Greece

Pinus brutia
Last Saturday (16/04/2016) amateur botanist Steve Lenton and I visited the heavily wooded area around Kato Symi (Crete, Greece). We were immediately alarmed by the state of the pine trees (Pinus brutia) in the area and I decided to investigate the cause or causes.

Thaumatopoea pityocampa caterpillar

The first suspect was the Pine Processionary  Moth, Thaumatopoea pityocampa due to the high number of nests which were visible. These cause massive defoliation of pine trees.

Closer examination of the trunks showed white, fluffy extrusions which looked similar to Pine Beetle pitch tubes.

Marchalina hellenica

The true culprit however was nearby in prodigious numbers: The Giant Pine Scale, Marchalina hellenica.

Honeydew (600x)

These produce the white fluff that is packed full of nourishing honeydew.

Apis melifera
 This honeydew is an important food source for the Honey Bee, Apis melifera, from which seems to “originate all the pine honey in Greece” [Portrait of an Insect: Marchalina hellenica http://www.friederikeerlinghagen.de/vita_2.php]. There were a lot of bee hives in the area and it is not unknown for beekeepers to deliberately introduce this pest (even if ultimately it is like killing the goose that laid the golden egg).

Meanwhile, at the base of the tree the Pine moth caterpillars were not having it all their own way as they were being trapped in sticky threads that appeared to be emanating from the ground.

My guess (and it is only a guess) is that this is some sort of fungal mycelium.If so, what is it and does it have any connection to either the caterpillars or the scale insects? There is still a lot of investigation to be done on plant/fungi relationships and I wonder if the tree could be ‘calling up’ a fungus as a defence mechanism or if the fungus is attacking an already weakened tree.

 The following photos show the threads at different levels of magnification and I welcome feedback from mycologists and entomologists on this fascinating (if destructive) set of interactions.



 Steve Daniels, Crete, Greece, April 19th 2016.

I originally posted this on Facebook (Naturalsits Group) and LinkedIn (Ecology & Evolutionary Biology). As comments are coming in from both groups as well as Steve Lenton's Facebook Group (Cretan Flora) I have decided to publish it here complete with comments from all sides in order to keep the conversation in one place. SD 27th April 2016. 

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