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Horse Chestnuts Are Under Threat from the Larvae of a Moth

Updated on August 7, 2015

Signs of foliage damage

The tell tale signs of a leaf miner at work.
The tell tale signs of a leaf miner at work. | Source
They attack various species of plants including tomato foliage as the photograph demonstrates.
They attack various species of plants including tomato foliage as the photograph demonstrates. | Source

Notes from a Lancashire Countryman

Leaf Miner damage , or the symptoms, are familiar to many gardeners. There are many different species that attack many different species of plants. In my Hub "Galls and other growths on trees" I touched upon one species that has caused a great deal of concern to conservationists and statutory nature bodies here in the U.K.-It is the Horse chestnut leafminer, Cameraria ohridella. It first attacked trees in the south of England but now it is spreading northwards at an alarming rate. There are fears that this pest may cause as much damage to the horse chestnut Aesculus hippocastanum, as the Larvae of the beetle that spread Dutch elms disease which decimated the population of elms.

The horse chestnut leaf miner is the larvae of the moth Cameraria ohridella which belongs to the order Lepidoptera and the family Gracillariidae. The moth is tiny and measures around 5mm. long. the fore wings are bright brown with thin silvery stripes, the hind wings are dark with long fringes.

Adult moth

Adult moth Cameraria ohridella
Adult moth Cameraria ohridella | Source

A relatively new species

This moth is relatively new to Britain indeed, the first recording was made in 2002 in the south of England, but experts surmise that it may have arrived on our shores in 2000-2001. Studies have revealed that the rate of spread may be as much as 50-70 kilometers a year and now it is recorded across much of England and Wales.

The flight of the adult moth is the most obvious ways of the spread, however, it is thought that infected leaves may fall on vehicles such as cars, lorries and forestry machinery, and are conveyed to new areas in this manner.

The Larvae

The larvae  are the leaf miners.
The larvae are the leaf miners. | Source

Biology of the leaf miner.

Each female moth lays between 20-40 eggs arranged singly on the upper surface of the leaf. Once they hatch which is two to three weeks later the larvae evolve through various feeding stages. The first of these stages sees the larvae creating a small cavity{mine} in the tissue of the leaf. These cavities are much enlarged as the larvae grow. the damage may expand over several centimetres.

About 4-5 weeks after they hatch the larvae start to pupate. Adults emerge about three weeks later. the moth depending on conditions may raise many generations. If the weather is dry and hot they are capable of producing 5 generations per season, however, here in the cooler western climate three generations are more the norm. The last generation will pupate and pass the winter in this manner. They are well able to withstand hibernal conditions and prolonged frost will not kill them thus they can survive hard winters.

Healthynew foliage


Infected trees

Heavily infected trees can be badly damaged with infected leaves turning brown and falling giving and autumnal appearance even during July. early leaf fall denies the tree the chance to accumulate enough nourishment and reserves to see it through the winter thus being denied the vigorous growth associated with the spring. repeated infestations over a period of time weakens the tree and can cause the tree to die.

Badly infected folaige

Infected foliage shrivels and dies
Infected foliage shrivels and dies | Source
The foliage in the bottom left hand corner is an example of how the leaves should look at this time of the year.
The foliage in the bottom left hand corner is an example of how the leaves should look at this time of the year. | Source

Spread has been fast

The leaf miners have spread so rapidly that predators have yet to catch up with them. It is known that at least three species of the tit family the great, blue and marsh tits predate them, however, studies have revealed that this only counts for about 2-4% of the larvae. It is also estimated that all predation by creatures only counts for about 20-22% of the leaf miners.

If the leaf miner infestation occurs on a tree at the same time as another of its enemies, a bacterium known as Pseudomonas syringae, the threat to the tree is even greater. The symptoms of this attack can be identified by staining to the main trunk caused by bleeding sap. This phenomena is referred to as a canker. According to a Forestry Commission Survey over 50,000 trees are now infected by this canker in the U.K. and this is thought to be if any thing under estimated.

One can only hope that nature will eventually rid the trees of these attacks or another species of our majestic trees may lost. The countryside would be a much poorer place without them.


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    • D.A.L. profile imageAUTHOR


      8 years ago from Lancashire north west England

      Hi tonymac04, good to see you here. Thank you for your visit and for taking the time to comment. Best wishes to you.

    • tonymac04 profile image

      Tony McGregor 

      9 years ago from South Africa

      Grew up reading about "conkers" - can't quite remember which schoolboy literature it was, though? LOL!

      Thanks for sharing this very troubling information. Hope something can be done to rescue the situation.

      Love and peace


    • D.A.L. profile imageAUTHOR


      9 years ago from Lancashire north west England

      dallas93444, thank you for your visit and for leaving your appreciated comments. Best wishes to you.

      Hi Darski my loyal friend. glad to hear your are back home and hope all is well for you both. Thank you for your usual glowing comments which are warmly welcomed. Love and best wishes to you always.

      sofs, thank you so much for your encouraging comments they are truly appreciated. You are always welcome here. Best wishes to you.

      leni sands, how are you, thank you for stopping by the tree that lacked conkers this year may well have been "resting" most trees only produce abundant crops every two seasons. Thank you for your visit, I enjoyed your hub on your long walk. Best wishes to you.

    • leni sands profile image

      Leni Sands 

      9 years ago from UK

      Great hub. We have lots of conker trees around us. We were riding along the canal towpath the other day and at one point you couldn't pedal for conkers on the path. The trees looked pretty healthy though (for now).

      There is one tree, not too far from us on the canal bank that has given us cause for concern though because this year and last year it didn't seem to produce many conkers. Having now read this I will look more closely at it next time we go by. Thanks for sharing.

    • sofs profile image


      9 years ago

      Your concern and desire to protect nature is admirable. I have never seen a chestnut tree but those pictures tell me that they look awesome like a emerald canopy. Your pictures, I just love them, they never cease to evoke that sense of awe and wonder. Honestly you are an amazing lens man.. I just come here to look at your artwork!! :)

    • Darlene Sabella profile image

      Darlene Sabella 

      9 years ago from Hello, my name is Toast and Jam, I live in the forest with my dog named Sam ...

      HELLO my dearest friend, oh yes I have missed you so much and I am now back home, so much to tell you but for now I must say I am happy to return to your awesome hubs, and this one is of course quite sad, how each form of life feeds of another...thumbs up love this hub and love you, darski

    • dallas93444 profile image

      Dallas W Thompson 

      9 years ago from Bakersfield, CA

      Great information that can make a difference. Thanks for sharing.

    • D.A.L. profile imageAUTHOR


      9 years ago from Lancashire north west England

      Hi ankigarg87 nice to meet you. Thank you for your visit and for leaving your appreciated comments. Best wishes to you.

      SiverGenes, thank you so much for encouraging and welcome comments . Appreciated.Best wishes to you.

      agvulpes, Goevrment and statutory conservation bodies are currently undertaking studies and surveys in the hope of preventing its spread. The elm tree problem is another serious issue. Thank you for reading and for leaving your appreciated comments.Best wishes to you.

      2uesday, you are so right about the detrimental affect on our countryside and towns. Thank you for reading and for leaving your welcomed comments. Best wishes to you.

      Hi Money Glitch, it is, I hope, just a matter of time before the predators catch up with this moth and their larvae. It is until then that the trees are under serious threat. Thank you for reading and for leaving your appreciated comments. Best wishes to you.

    • Money Glitch profile image

      Money Glitch 

      9 years ago from Texas

      Interesting story. Too bad there is not a bird or another insect that loves to eat this moth and it's larvae. Thanks for sharing this information. :)

    • 2uesday profile image


      9 years ago

      I love these trees so I do hope that they will not suffer the same fate as the elm trees did. I hope that nature will deal with the problem, our country-side and towns would not seem the same without the majestic Horse Chestnut trees and their leaf canopies. Thank you D.A.L.

    • agvulpes profile image


      9 years ago from Australia

      Very informative Hub, This looks like it has become, or could become a very serious problem. Is your government doing anything on a large scale to beat this pest?

      We are having trouble here with the Elm Tree bug and it is spreading all over the state!


    • profile image


      9 years ago

      I learned a lot here. Thank you - your articles are truly wonderful and I'm marking several for future referral. Rated UP!

    • profile image


      9 years ago

      amazing hub and knowledgable also


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