Leaf Mining

There are a couple of Holm Oak, Quercus ilex, in the copses of trees between the two meadows. We estimate that these copses were planted about 20 years ago, looking at relevant historical Google Earth photos. While some of the trees in the copse such as Whitebeam still feel like juvenile trees, the Holm Oaks are very large and have the aura of fully grown trees, although they are not the 20 to 27 metres tall quoted for a properly mature Holm Oak tree.

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One of the 20 year old Holm Oaks in the copses dividing the two meadows

Holm Oaks are evergreen oaks, native to the Mediterranean, and actually classed as alien invaders in the UK since they reduce native biodiversity. They are not particularly frost hardy and so seen more in the south of England than the north. They were introduced into Britain in the 16th Century and those first Holm Oaks grown from acorns in Britain are apparently still going – in the grounds of Mamhead Park in Devon.

In the Mediterranean, the acorns of the Holm Oak are an important food for the free range pigs reared for Iberico ham production and it is one of the top three trees used in the establishment of truffle orchards. But none of that sort of stuff is going on here. We value our  Holms for their dense evergreen cover which acts as a wind break and shelter for animals as the strong coastal winds rage across the meadows, as they are doing at this very moment as storm Frank, the last storm of 2015, works its way across Britain.

Our Holm Oaks, however, are infested by Leaf Miners. All the leaves over the entirety of the trees are covered in the brown marks of tunnelling larvae.

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As part of our continuing need to educate ourselves as to whats going on out there, I have been looking into this…….

It would appear that these trees have been infested with the micro moth Ectoedemia heringella. This species has come from the Mediterranean area as indeed have the trees themselves but the moths have followed 400 years later. They are thought to have been introduced by mistake as part of the trade in garden plants – first discovered here in 1996 in Greater London but its identity not confirmed until 2002. They are now reasonably rampant across the South East of Britain and currently it is not known how best to control them. This is now under investigation by Kew – parasitic wasps are mentioned – but for now there is nothing to be done.

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Ectoedemia heringella moth

 

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Ectoedemia caterpillar

 

The adult moths emerge in June and July, although they are rarely encountered – presumably they do not come to light and I won’t be collecting them in my trap next summer. However, they can be reared from the mines if you collect them in Autumn and Winter, perhaps by picking some leaves and putting them in some water in an enclosed place until June? I am not sure that I am going to do that, but I will be keeping an eye out as I pass these trees from now on to see whats going on.

 

 

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