Prunus spp. dieback

[Evan Sussman]

A client has a row of plum trees that she reffered to as flowering plum. If I am correct it is Prunus cerasifera.

The problem the trees have is that each season, (she has noticed at least the past 3 seasons) some of the tips will dieback/wilt and not recover. Now the trees are getting somewhat thin in the canopy. They have not had care such as crown cleaning, or thinning. I think that may have helped the overall health, and resilience of the trees, though I believe this is some other disease that is affecting it now.

I have/will attach some pictures of what I am seeing.

The first picture is of some insects that I found on a stem below where dieback had happened in a previous season. These white flying insects were distributed throughout the trees. There were enough of them that it was likely that you would find at least 5 on any given 4sq' of canopy.

I also found one caterpillar that I did not photograph inside some of the leaves that were curled up. Since I only found one I have ruled it out as a cause.

Am I correct in the species?
What are common diseases?
Has anyone seen this?

I'm also going to contact the local WSU extension and see what they have to say.

Thank you for your help, I'm new to the area and to the specifics of disease/insect identification.

 

[Evan Sussman]

In this picture you can see the wilt/dieback. Eventually this dies completely.

 

[Evan Sussman]

A shot of one of the white flying insects, and possibly it's eggs?

 

[Evan Sussman]

another insect nest...

I'm sorry about the improper focus, for small stuff the smartphone cameras fall short.

 

[Evan Sussman]

According to an article on OSU's plant disease handbook:
http://pnwhandbooks.org/plantdisease/

http://pnwhandbooks.org/plantdisease/hos...-blossom-blight

It looks a lot like a brown rot cause by Monilinia fructicola and M. laxa

 

[Evan Sussman]

I should also note that the trees are fully exposed for most of the day, and they have good air flow.

 

[mrtree]

Monilia

 

[mrtree]

Look for wilt like symptoms after flowering and swelling twigs below the blight. Like a combination of wilt and black knot.

 

[Evan Sussman]

10-4, Thanks Mr Tree. Is the wilt a separate disease, or are those both symptoms of Monilia.

According to wikipedia both spellings are correct.

http://en.wikipedia.org/wiki/Monilia


From what I remember, and I did look for knots, I didn't see them. I'd done a brief study of flowering plum diseases before I went to look at the trees, and black knot was at the top of the list, and easy to ID.

 

[mrtree]

The wilt and stem swelling are both caused by Monilia. The swelling is like the start of black knot but does not progress.

After the wilting lots of dead tips. I find pruple-leaf sandcherry and flowering almond to be the most common landscape plants to be affected by the disease (perhaps because they are very common in many lanscapes I deal with).

Pruning may help but the disease is very common in some fruit tree areas. Perhaps removal and replacement with alternative species may be wise as managment with chemicals and pruning of a few shrubs is not worthwhile.

 

[SMAdams]

Another symptom of Monilinia (brown rot of stone fruit) is resin oozing out from the stem, especially in the spring.