Verticillium wilt is not necessarily characterized by blackened stems (more symptomatic of Pseudomonas) nor always by the streaking of the cambium. However the pith or center of the stems/branches is typically discolored or darkened, indicating failure of the vascular system. For an accurate diagnosis, take a good sample branch, preferably from as low on the tree as possible, to your local extension office.

The pathogen that causes VM can be present in any soils. It can often persist in a dormant state for many years and trggered into action by specific root exudates. Generally, a susceptible species that is in good health and free of stress can coexist with this soil-borne pathogen without problems. But if under stress for whatever reason or if damage has been done to the root system (cultivation or other root disturbance, poor drainage or excessively wet soils, etc.), then this very opportunistic pathogen can easily invade root tissue and infect the tree. Just because one tree in a garden becomes infected with VW does not necessarily mean the pathogen will affect any other nearby susceptible species.

I would also note that an effected area down the branch or towards the top of the trunk won't emmidiatly effect the top branches ...they often leaf out but unable to get sap IE: food they die since the blackness is a sign of cambium death..so I don't see this as uncommon to have green top branches with dead leafs I have personally seen this...Everything below the blackened area should be ok but it may travel downwads too and zap the whole tree...I have found once the blackened area is on the trunk below the branches you better get your trumpet out for taps..David

Thank you for the responses. I will try to get a branch to the local extension office for a diagnosis. Gardengal, can you give me a quick summary of what a pseudomona is? I googled it but only got very scientific links. Thanks again!

Pseudomonas syringae is a relatively common bacterial blight that affects a number of woody plants. It is encouraged by cool, damp springs (welcome to the PNW!!). Although the attached link does not specify, it is common with Asian maples and some cultivars more than others. It seems to be extremely prevalent with 'Sango Kaku', for example (I worked with a client just yesterday who had a whopping infestion of pseudomonas on a young coral bark - he had to remove half the tree).

In your case, I'm not sure this is your problem and would be reluctant to make any kind of definitive diagnosis based on just a verbal description. Based on what you've described, I'd lean more to VW than to pseudomonas :-( Sorry. Pseudomonas generally will affect branch tips and travel downward to the more mature tissue, so you would immediately notice blackened stems and wilted foliage before you would see black bark on the trunk or mature branches. Often you will see the development of cankers in the mature tissue.

Based on the horrible late fall and winter weather we experienced, I'd expect to see a number of problems generate with not yet well-established maples and other plants in this area and so far my expectations are being confirmed.

Let us know what the extension service determines.

Here is a link that might be useful: Pseudomonas syringae

It is also common to see or more common to see Japanese maples exhibit the canker or systemic form of pseudomonas rather than the blight or topical shoot infection. while the latter is common in nursery and production and in the "wetter" locales of maple growing climates, canker and internal forms are more often seen and poorly recognized.

Traveling in rootstocks and dirty scion wood (although it can also be acquired from the environment), the canker form of the disease readily weakens bark cuasing open lesions and splitting. Often this form will make the bark of the maple much more suseptible to sun scald or burn even when no real visible signs of the canker are present. These leasions should readily be treated or pruned out as not to become enlarged and provide an entrance point for other infections and especially various types of borers.

The severe wilt, quick onset form, of verticillium that has most likely killed your plant is very similar to the quick onst form that infects agronomic crops, grains, etc. You will see the onset of wilt happen very quickly in plants from 0-10 years of age with blackened or very dark brown-black stems and shoots that rapidly lose turgidity with no warning. This is much differnet that the very slow acting alboatrum form that works over long periods of time, often in conjuction with other infections, and shows an entirely different subset of characteristics and colors. This form often enters from the soil through weakened roots systems.

Sorry about your tree. I have been there as well.