I just came home from work to find my yellow Acer is looking worst for wear. It's in a pot temporarily (for 2 month) and one of the stems seems to have dried out and died over the weekend and the leaves are all brown. It's so sudden and has just happened this weekend (see pictures attached). It's odd because it's only one stem and the stem seems to have changed colour and turned red. I wondered if it is Verticillium? If not what could it be? Is there anything I can do? Many Thanks
Hard to tell, looks like there may be some darkish streaking in the top branches, which would indicate V. wilt. The timing is also right... Whatever it is was probably brought on by the stress of repotting, or the change in watering regime. Make sure the soil is draining very freely and drying out between waterings. In any case, your options are limited. IMHO you need to cut off the effected branch immediately, making sure that the cut is in clean wood. Remember to sterilize the secateur after every cut. Because of the discoloration I think this branch is going to die and there's no point trying to save it. Then treat the branches with a copper-based spray, e.g. Bordeaux Mix. Repeat the treatment every 3 weeks or so during the summer. The copper seems to slow the wilt down somewhat, and will help treat other bacterial infections if that is the problem. I wouldn't move it again (meaning repot or plant in earth) until after leaf drop. The good news is the rest of the plant looks healthy, and if it is verticillium maples can often live for years with the condition, depending on the aggressivity of the pathogen. HTH -E
I've trimmed one of the dead(ish) branches off and have taken a few more pictures to help if anyone can identify what it might be and whether cutting all of the dead stem is definitely the right action to take...let me know your thoughts. The pics show the inside of the newly cut branch (so people can see the section) and also some close-ups of the dying branch.
I get the impression the more common problem is actually bacterial blight (Pseudomonas). When checking for verticillium you shave the stem vertically to see if there are brown lines of clogged vascular tissue running the length of the branch. http://pnwhandbooks.org/plantdisease/maple-acer-spp-bacterial-leaf-spot-and-dieback
I also thought it might be Pseudomonas or similar bacterial issue. Another thought is that the tags look as if they have been on the plant for a long time, it might be worth checking the tie is not cutting into the bark as it seems to be the stem with the label that is suffering.
