Making observations of the amount of damage that the leaf-mining moth has done to trees, means that you have to remember to submit what you saw and where you saw it when you get home and turn on your computer.
What would be perfect would be if people had a little device to make those records while they were looking at the tree. It would be even better if it would record their location automatically, and even allow them to submit a photo of one of the leaves, while they were there.
Aha! Smartphones would be the perfect tool!
...And so was born the idea of the LeafWatch app.
Wednesday, 9 May 2012
Mission: alien moth survey
How long? A minute.
When? Anytime from mid June to late autumn.
How? Make observations and (1) enter records on the website, or (2) use the LeafWatch app for smartphones.
Why? Does the damage caused by the moth increase with the length of time that it has been present in a location?
Anecdotal evidence suggests that the amount of damage caused by leaf miner increases over the first few years that the moth has been present in a locality. For example, many horse-chestnut trees in London are almost completely defoliated by early August, so it looks like autumn has come early, but currently in parts of south Devon, horse-chestnut trees only have a speckling of leaf mines by the middle of September.
Part of the aim of our science is to provide data to confirm anecdotes such as these, and to estimate precisely how quickly the levels of damage increase with the length of time that the moth has been present.
We have asked people since 2010 to score how much damage is being done to the horse-chestnut tree leaves. They can enter their location and date so that we can assess the damage. Since 2011 people can also get involved with the LeafWatch app. For those who have smartphones, this is a really convenient way of gathering records - each record is associated with a photograph (which helps us confirm
Firstly, the distribution of many animals and plants in this country is recorded in 10 x 10km squares (based on the Ordnance Survey grid), and the horse-chestnut leaf-miner is no different. Forest Research have been collating the 10 x 10km square records of the horse-chestnut leaf-miner to monitor its spread. We pass on any confirmed records from new 10 x 10km squares to Forest Research to help with our understanding of its spread. (We confirm records with a photograph, which is either requested via the Conker Tree Science website for new squares, or is automatically included in the record from the LeafWatch app.)
Records of its damage
Secondly, we are assessing how the amount of damage to the leaves is affected by the length of time that the moth has been present. This is clearly shown on the LeafWatch app website.
We are also doing statistical analysis to confirm the observations, while taking account of the time of year (because the amount of damage increases throughout the year as the moths reproduce). The statistics we are using is a fairly complex method called ordinal regression.
When? Anytime from mid June to late autumn.
How? Make observations and (1) enter records on the website, or (2) use the LeafWatch app for smartphones.
Why? Does the damage caused by the moth increase with the length of time that it has been present in a location?
Anecdotal evidence suggests that the amount of damage caused by leaf miner increases over the first few years that the moth has been present in a locality. For example, many horse-chestnut trees in London are almost completely defoliated by early August, so it looks like autumn has come early, but currently in parts of south Devon, horse-chestnut trees only have a speckling of leaf mines by the middle of September.
Part of the aim of our science is to provide data to confirm anecdotes such as these, and to estimate precisely how quickly the levels of damage increase with the length of time that the moth has been present.
We have asked people since 2010 to score how much damage is being done to the horse-chestnut tree leaves. They can enter their location and date so that we can assess the damage. Since 2011 people can also get involved with the LeafWatch app. For those who have smartphones, this is a really convenient way of gathering records - each record is associated with a photograph (which helps us confirm
What do we do with the records?
Records of the moth's spreadFirstly, the distribution of many animals and plants in this country is recorded in 10 x 10km squares (based on the Ordnance Survey grid), and the horse-chestnut leaf-miner is no different. Forest Research have been collating the 10 x 10km square records of the horse-chestnut leaf-miner to monitor its spread. We pass on any confirmed records from new 10 x 10km squares to Forest Research to help with our understanding of its spread. (We confirm records with a photograph, which is either requested via the Conker Tree Science website for new squares, or is automatically included in the record from the LeafWatch app.)
Records of its damage
Secondly, we are assessing how the amount of damage to the leaves is affected by the length of time that the moth has been present. This is clearly shown on the LeafWatch app website.
We are also doing statistical analysis to confirm the observations, while taking account of the time of year (because the amount of damage increases throughout the year as the moths reproduce). The statistics we are using is a fairly complex method called ordinal regression.
Results from 2011: summary
During 2011 we had two missions running: the alien moth survey and the pest controller mission. People could take part in both missions via our website, and they could take part in the alien moth survey via the LeafWatch app for iPhones and Android smartphones.
We had 710 records from 250 people via the website (but many more took part via the smartphone app). From the snapshot of the results at the end of the season we can see that the leaf-mining moth is widespread over most of England, although it appears less abundant in the south-west of England. In Wales the records are less widespread, but we cannot tell if that is because they are fewer leaf-miners or fewer people sending in records. Again, there are few records in the north of England, but this does fit with other people's findings that it has not spread right into the north of England.
We had received positive records from as far north as Newcastle, Carlisle and Dundee, but only the record from Newcastle has been confirmed with a photograph. So, up until the end of 2011, the horse-chestnut leaf-miner still had not been confirmed in Scotland.
We had 383 results from 120 people via the website. This is a more involved study than the alien moth survey and has to be started in a one week period at the beginning of July. However, from the comments we received, those people taking part really enjoyed it.
Like last year, there was, overall, a very small number of pest controllers that emerged.
One person noted that there was a big difference in the numbers of pest controllers reared from trees that were very close together, which is an intriguing finding.
Although the graph shows a huge proportion of pest controllers in the square covering Cornwall, it is worth noting that these graphs do not show the 'sample size'. We received just two records from Cornwall, and both had quite high numbers of pest controllers. We received a record from Bath with a similarly high number of pest controllers, but lots of other records with very few pest controllers, which evens out the results. Of course, it may also be something specific about Cornwall - but in science it is wise not to base conclusions on small sample sizes.
Mission: alien moth survey
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| Website results for the alien moth survey, 2011 |
We had received positive records from as far north as Newcastle, Carlisle and Dundee, but only the record from Newcastle has been confirmed with a photograph. So, up until the end of 2011, the horse-chestnut leaf-miner still had not been confirmed in Scotland.
Mission: pest controllers
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| Website results for the pest controller mission, 2011 |
Like last year, there was, overall, a very small number of pest controllers that emerged.
One person noted that there was a big difference in the numbers of pest controllers reared from trees that were very close together, which is an intriguing finding.
Although the graph shows a huge proportion of pest controllers in the square covering Cornwall, it is worth noting that these graphs do not show the 'sample size'. We received just two records from Cornwall, and both had quite high numbers of pest controllers. We received a record from Bath with a similarly high number of pest controllers, but lots of other records with very few pest controllers, which evens out the results. Of course, it may also be something specific about Cornwall - but in science it is wise not to base conclusions on small sample sizes.
Wednesday, 2 May 2012
About the moth 2
Where has it come from?
The horse-chestnut leaf-miner was discovered in the Balkans (near Lake Ohrid in Macedonia) in the late 1970s. It was then discovered in Austria and from these two focal points, the moth has spread rapidly throughout Europe.The spread of the moth in Britain
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| The spread of the horse-chestnut leaf-miner. Data from Forest Research |
It has spread quickly through Britain, so that by the end of 2011 it was widespread south of the Pennines. Its distribution in south-west England and Wales is patchy than elsewhere in sourthen England, this is probably due to the smaller number of horse-chestnut trees in these area and that the leaf-miner has only recently arrived in these regions.
How quickly does it spread?
Studies across Europe suggest that the moth spreads at an average rate of about 30km per year.How does it spread?
The moth can spread by flying. It is a very small moth and probably is a weak flier. However there can be so many adult moths emerging from the leaves of an infested tree that just by chance a few inidividuals may manage to travel a mile or two.The main way in which the moth spreads long distances is probably by 'hitch-hiking' on vehicles. Our anecdotal evidence supports this notion. A couple of years ago I was looking round a south Devon coastal town for the horse-chestnut leaf-miner and the only place I found it was in the car park of a holiday resort, suggesting it had hitch-hiked with holiday-makers. A few months later I was photographing a horse-chestnut tree, then walked back 20 metres, got in the car and discovered several of the moths had come in the car with me.
About the moth 1
The horse-chestnut leaf-mining moth
The moth whose caterpillars are causing the damage to horse-chestnut trees is the horse-chestnut leaf-mining moth, which has the scientific name Cameraria ohridella.It is known as one of the 'micro moths', to distinguish it from the typical 'macro moths', which are the larger moths often attracted to light.
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| A mating pair of horse-chestnut leaf-mining moths. © Dave Kilbey |
The adult moth
The adult moth is tiny - just a few millimetres long - and very attractive, with white stripes on glossy bronze wings. Many people we have spoken to are surprised that the moth is so small. When the adults emerge, there can be so many flying close to a horse-chestnut tree that the tree appears to shimmer.Its leaf-mining larvae
It is the larvae (or caterpillars) of the horse-chestnut leaf-miner that do the damage and feed on the leaves of the horse-chestnut. Many caterpillars are external feeders, but the horse-chestnut leaf-miner is different. Its larvae actually live inside the leaf and they 'mine' the leaf forming what are called, unsurprisingly, leaf mines. As they feed on the green tissue on the inside of the leaf, they leave the upper and lower layers of the leaf (the 'epidermis) intact, so the larvae remain protected.The remaining epidermis of the leaf is translucent, which is why the leaf mines look whitish when they are fresh. After a few weeks the epidermis of the leaf mine dies and turns brown.
Each larvae produces a singe leaf mine, which eventually ends up about the size of half a person's finger. When infestations are large, the mines coallese and the larvae form groups searching for the remaining green tissue.
The larvae have incredible adaptations for living inside a leaf. They are have flattened so they can easily move about in the leaf mine and they have chisel-shaped heads with pointed moutparts so they can easily eat the fresh green tissue at the edge of the leaf mine.
Tuesday, 1 May 2012
Mission: pest controllers
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| Conker Tree Science |
Believe it or not there are dozens of different kinds of tiny wasps (only distantly related to the stinging wasps that we are so familiar with) that attack the horse-chestnut leaf-miner. These wasps are so small that they lay their eggs inside the leaf-miner as it is eating the horse-chestnut leaf from the inside out! The developing wasp larvae eat the leaf-miner from the inside out and then burst out of the caterpillar, in the process killing it and so acting as a natural pest controller.
Can these potential pest controllers actually help by parasitising enough of the leaf-miners to control it's numbers? Given that we have so many of the leaf-miners in this country it would seem that they cannot, but we are interested in finding out more about them.
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