Question
Hi,

We have had a Japanese Plum Tree for over 20 years that offers beautiful shade and has been quite healthy. This year half of the tree is dying and there is a yellowish power on the limbs, it almost looks like moss. The parts of the tree that have this have dried dead limbs. Now it looks as if this yellowish power is spreading thought out the rest of the tree. Don't know what is happening or what to do. Any help would be appreciated. Thanks,

Josephine

Answer
Hi Josephine...Sorry if I have this wrong, that is why botanical names are important to me in helping you.  So if in fact this Japanese Plum is a loquat here is what you can do. The only thing I come up with is Fire Blight...

SYMPTOMS
Cytospora is considered a weak parasite and invades only weakened or stressed
trees. It gains entry through injuries in the bark caused by machinery, sun scald, frost,
pruning wounds, broken branches, mechanical shakers, and insect injury. Cankers on
trunks or branches are sunken and range in color from brown to gray depending on the
host species. The canker expands slowly over a period of months or years and may
eventually girdle the branch, causing it to die. The fungus may produce small (1 mm)
pimple-like bumps in which black fungal structures called pycnidia are embedded. The
presence of pycnidia can be confirmed by slicing the bark with a knife where raised
areas are evident. Pycnidia are quite common and obvious on mountain ash, cherry,
and birch.
CAUSE
During warm, wet weather, brown to orange-colored masses of spores
(analogous to seeds) are extruded from the pycnidia in a tendril-like mass. These
spores are carried by rain or blown by wind to susceptible sites where they cause new
infections. Optimum conditions for Cytospora infections occur in the spring when
daytime temperatures are 60 to 80F. The fungus continue to grow and produces spores
during the warm weather months.
CONTROL
Preventing infection is the best way to control Cytospora. There are no fungicides
which are effective in controlling the pathogen once it is in the tree. No single method of
control can be used to prevent this disease; therefore, it is necessary to use several of
the methods described below to maintain healthy plants.
Maintain high tree vigor. Trees should be watered deeply during dry summer
months to prevent drought stress. Fertilize in the spring to keep trees vigorous. Avoid
late summer applications of nitrogen because it stimulates growth in autumn which does
not harden off before winter. Trees stressed with iron chlorosis are particularly
susceptible to Cytospora infections.
Keep soil cool and moist by frequent irrigation.