By Scotsgran
Scotland 
Can someone please tell me what has happened to cause this damage on my rhubarb plants. I have two varieties. Champagne is a very old plant. I have had it growing happily and healthily in a pot for years. I decided to split it last year. I planted a healthy root under the apple trees. I also bought a newer variety named Raspberry Red. It is planted four foot away from the Champagne, also under the apple trees. The stems and leaves of both plants are quite disgusting. There are jelly like blobs and scarring on both the leaves and stems. There are lots of millimetre long insects running about on the undersides of the leaves. They run too fast for me to get a decent photograph of them. The apple trees are all healthy and fruiting normally.
31 Aug, 2013
Answers
Could they be thrips?
Nasty tiny itchy things, thin and black, and get everywhere
31 Aug, 2013
I've often had those jelly bits on the stems and not thought anything about it - just thought it was what happened towards the end of the summer. You can just cut it off. If the stem's not much good for stewing you can always make jam with it - have you tried half and half with MaMade marmalade making stuff? Its really very nice!
Never seen the little black insects though.
31 Aug, 2013
Thank you all for your answers but I would appreciate knowing what has caused it. There is not a lot of undamaged stem left. I don't fancy eating the fruit at all Stera but the Mamade mixture sounds interesting. I make three fruit Marmalade with a tin of orange mamade and a tin of the lemon mamade plus a tin or two of grapefruit pieces in juice. Its delicious.
31 Aug, 2013
Do try it if you get the chance Scotsgran. The lemon one isn't always easy to find though.
1 Sep, 2013
Our local Coop always has it and the local Sainsburys are also regular stockists. Is it the lemon one you use or will either mamade be okay?
1 Sep, 2013
I've never attempted fruit and veg so just a general thought that as the leaves aren't eaten could it be worth picking the crop before it gets worse or has it spread down into the stems? The stems look like their just about ripe.
I think I'd burn the leaves and any affected material as soon as possible in case it's a fungal infection.
You don't say what you did with the other piece of the old Champagne root - is that growing healthily?
(Middle & Bottom picture looks like there might be a couple of baby slugs as well.)
31 Aug, 2013