Monday, 2 July 2012

What about the leaf litter?

From time to time we've had queries about leaf litter under horse chestnut trees, specifically whether it is a problem and, if so, what should be done about it.

It was for this reason that we invited people to record the vegetation under their trees in 2011 when recording the amount of damage that the moths had done. The final analysis is close to completion, but a look at the preliminary results suggests that:

The presence of mown lawn under horse chestnut trees, which was taken as a measure that leaf litter would not have been present over the winter*, is related to a reduced amount of damage recorded for any particular location and time.
In other words - the data people collected strongly suggests that clearing leaf litter is worth it to reduce damage to your tree!

2 trees just 50m apart, photographed on 2nd July. The one on the left had leaf litter under it during the winter. The one on the right did not have leaf litter under it during the winter. Of course, the presence of leaf litter may not be the only factor affecting how much damage there is from the horse-chestnut leaf miner, but it could have been important.

(* Of course, some trees with other types under the tree canopy could have had their leaf litter cleared away, but our observations suggest that this would be a minority. If we had been able to take that into account that would have strengthened our results. So, why did we not directly ask people whether there had been leaf litter under the tree the previous winter, or whether it had been cleared away? The answer is that we wanted this project to be open to anyone - so they could answer all the questions even if passing a tree they had never seen before.)

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