Please Help! Black leeches on cherry tree!

Hi all...
I have a cherry tree that's around four years old and yesterday noticed several black leeches on the leaves approx. 1cm long. I squished all the ones I could see/reach, but obviously there must be others on the rest of the tree.
Please could you tell me what they are as I can't find info about them and have never seen them before? Also, what are they doing and are they very damaging to the tree? Finally, how do I kill the rest and protect my tree from them (how did they get there in the first place)? Thank you very much. I hope you can help.
Around a third of the leaves are orange now and I don't know if this may be due to the leeches or if it's turning early for autumn. The tree is in Northumberland.

'The Cherry Slug
The cherry slug is also known as the pear slug and it very much looks like a leech. These slugs are actually insects that are well known for the potential damage they may do to many common fruit bearing trees. They have slender bodies and thick, round heads. Dark green, orange and slimy in appearance, the cherry slug begin feeding on trees in mid to late summer and again in the fall. The most damage is generally done by the second generation that comes to life in the fall. Insecticides are effective in treating and removing cherry slugs from a tree. Depending on when it is applied and the severity of the problem, more than one application may be needed.'

This is from an article by Ann Mitchell on worms and slugs that infest cherry trees, and may well be what you have found, NEJoy, and gives an idea fro contro, as well

I hope this helps 

'The Cherry Slug
The cherry slug is also known as the pear slug and it very much looks like a leech. These slugs are actually insects that are well known for the potential damage they may do to many common fruit bearing trees. They have slender bodies and thick, round heads. Dark green, orange and slimy in appearance, the cherry slug begin feeding on trees in mid to late summer and again in the fall. The most damage is generally done by the second generation that comes to life in the fall. Insecticides are effective in treating and removing cherry slugs from a tree. Depending on when it is applied and the severity of the problem, more than one application may be needed.'

This is from an article by Ann Mitchell on worms and slugs that infest cherry trees, and may well be what you have found, NEJoy, and gives an idea fro contro, as well

I hope this helps 

Hi, thanks. Yes I've read that already as it's the only info I could find online, but it says very little and doesn't give me the answers I need, so I'm hoping someone with experience of these and more knowledge about them will post a reply soon.

"Ha ha ha... you're so funny. I do know what slugs look like thanks!"

"Hi, thanks. Yes I've read that already..."

Gosh then, if you know so much about them already perhaps you can give everyone here a lesson.  

Thanks!




Make it more than clear who I'm quoting 

Quote from: sunshineband on September 01, 2011, 19:17

'The Cherry Slug
The cherry slug is also known as the pear slug and it very much looks like a leech. These slugs are actually insects that are well known for the potential damage they may do to many common fruit bearing trees. They have slender bodies and thick, round heads. Dark green, orange and slimy in appearance, the cherry slug begin feeding on trees in mid to late summer and again in the fall. The most damage is generally done by the second generation that comes to life in the fall. Insecticides are effective in treating and removing cherry slugs from a tree. Depending on when it is applied and the severity of the problem, more than one application may be needed.'

This is from an article by Ann Mitchell on worms and slugs that infest cherry trees, and may well be what you have found, NEJoy, and gives an idea fro contro, as well

I hope this helps 

Hi, thanks. Yes I've read that already as it's the only info I could find online, but it says very little and doesn't give me the answers I need, so I'm hoping someone with experience of these and more knowledge about them will post a reply soon.

I must have misunderstood you: sorry 

I thought you couldn't find any information and didn't know what these were.

This is something I have never come across before. Auntie's reference says it is a sawfly so its lifecycle is probably similar to the gooseberry sawfly which  most of us have seen.

If you just ignore them the lavae, which are apparently yellow but cover theselves in slime, will drop off the tree and pupate in the ground ready to emerge as flies in the Spring and re-infest your tree.

Your approach should be to break their life cycle. A combination of spraying the tree with insectacide to kill the lavae and cultivating the soil under the tree to expose the lavae to weather and birds. I presume that the flies fly to lay their eggs but somewhere I read that they might crawl up the trunk. In which case a grease band would help. Someone else may know more.
http://www.gardenseeker.com/plant_pests_problems/plant-pests/fruit_slugworms.htm