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  Sean Busby July 15, 2010 at 6:40pm

  Could well be an aphid problem Bob. There seems to be a lot of it about.
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  Robert Smale July 15, 2010 at 8:56pm

  There's no obvious sign of an aphid problem, but I will look again.
  The hedge was last clipped in October 09 and at that time the original end tree was removed as it was dead, then the same has happened to the next three trees.
  
  The dying off started before the drought. The hedge sits on top a 'Devon bank' and until this started it was a very vigourous thing!
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  Gary Hedges July 15, 2010 at 9:15pm

  I cut a leylandii last Sept and was mortified to find when I returned this year it had died back as you describe.
  
  However all of the surrounding gardens are the same, we had -18c here for several days on the trot but more importantly it has been the driest year since 1929 (http://www.channel4.com/news/articles/uk/driest+start+to+year+since...).
  I feel it is more likely to be caused by climatic conditions rather than Honey fingus.
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  Matt July 17, 2010 at 9:10am

  The old adage of a healthy plant has no enemies couldn't be truer. Before you go looking at pests and diseases its always worth looking at some of the more easily overlooked conditions. I always start at the bottom and work my way up, soil compaction being my fist stop, and since we have had a very dry period part of your problem may well be a hydrophobic soil problem, this in turn will weaken the plant and cause it to be laid bare to pests and diseases, I know others have suggested that aphids may be the cause and they may well be right, but on the whole a healthy plant, especially one as tough as the X Cupressocyparis leylandii, I would personally look on the aphid as the end result of the problem, not the sole cause.
  
  As to treatments, there are plenty of chemicals out there but I'd be a little careful doing anything with them, especially when there are so many safer, and in my opinion, better options. One old time method which has stood the test of time is washing up liquid, mix up a weak solution, maybe 1-10 in a sprayer, let it settle and spray where you can see the aphids, but I add, if you can't see the aphids anywhere or the "waste" they tend to leave, then I'd be a little surprised if its aphids. Back to the treatment, there are some very good "Ecco" oils, they work brilliantly and are very safe to use for all concerned but as I suggested, start at the bottom and work your way up, start with what I suspect is the "root" cause, drought damage, possible compaction or hydrophobic soils. You need to get some soil wetters on the roots, anything with seaweed in is brilliant at wetting soil, it allows the Mycorrhiza to flourish, allows the plant to function naturally and defend itself against bugs and nasties.
  Some pictures will be good and if you want to see if the drainage is an issue pour a bucket of water around their roots and see what it does, if it just runs away (although after this rain it may not) then you have your main problem, thats not to say other issues are NOT the problem, but as I said, healthy roots, healthy plants. If the water drains well, dig down, just a spades depth and see how wet the soil is there.... I bet I can guess your reply.
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  Matt July 17, 2010 at 9:28am

  Soap sprays will kill aphids, I have watched it under a microscope, but my point was not so much about the aphids, its about what is causing such a vigorously aggressive hybrid to suffer so badly from aphid attack, if the plant was healthy in the first place its better equipped to deal with problems. Treat the cause, not the effect.
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  Matt July 17, 2010 at 10:06am

  I agree, feeding is almost useless at this stage, but addressing what I suspect to be hydrophobic soil and possible root damage is a lot easier done, seaweed products are an often misunderstood area, people straight away think that its a feed and nothing else, its not, it does far more to encourage Mycorrhiza and root hormones than feeding ever could.
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  Matt July 17, 2010 at 5:14pm

  Given what the weather has been like recently I would be nervous about saying its water retention but as I said its hard to say anything without seeing it first hand or at the very least some pictures. Either way I am sorry to say that the prognosis isn't too good, Leyland Cypress are pretty unforgiving, thats not to say they won't recover but I seriously doubt they ever will, I have been to gardens before where the clients "tree surgeon" had come in and topped out a big Leyland hedge and told the client that the bare stumps he had left would "grow back"
  
  Coppicing on a miraculous scale.
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  Robert Smale July 17, 2010 at 6:16pm

  Had a good dig around the bas and root, removed bark and no sign what so ever of any Honey fungus.
  
  Also no signs on the hedge or around of any aphid concentration or problem.
  
  I tend to think it is a combination of old age, lack of feeding (there had been an old hedge on top this same bank before the leylandi were planted in the 70s) and the harsh winter.
  
  What worries me is the spread from the more exposed end, but that could all fit with the above.
  
  My suggestion to the client is to remove the dead trees, feed the remaining ones and sit back and see what happens. We can then take a really good look over the removed trees and have any testing done.
  
  Thanks for all the comments, I will update when we take action, just waiting for client approval to get on.
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  Matt July 17, 2010 at 6:48pm

  Hi Bob, to be honest, I think removal is the best bet, don't forget to have everything removed just in case its something else and not to suggest planting too soon, I personally would recommend leaving it in the hope we have another hard winter but I know clients like to have things done yesterday.
  As I said, I suspect that it is more to do with lack of water, Leyland Cypress is a pretty tough cookie and will stand up to most winters, of course it could have been damaged by the weight of the snow cover but as I said, without pictures or your first hand being there its hard, or "easy" for others to conclude.
  
  Bob Smale said:

  Had a good dig around the bas and root, removed bark and no sign what so ever of any Honey fungus.
  
  Also no signs on the hedge or around of any aphid concentration or problem.
  
  I tend to think it is a combination of old age, lack of feeding (there had been an old hedge on top this same bank before the leylandi were planted in the 70s) and the harsh winter.
  
  What worries me is the spread from the more exposed end, but that could all fit with the above.
  
  My suggestion to the client is to remove the dead trees, feed the remaining ones and sit back and see what happens. We can then take a really good look over the removed trees and have any testing done.
  
  Thanks for all the comments, I will update when we take action, just waiting for client approval to get on.