Euonymus. This thread may be helpful. http://forums.gardenweb.com/forums/load/pests/msg0817290317765.html

It appears to be one of the many (harmless) slime 'molds', actually not a mold or a fungus at all. These interesting organisms move across a surface, eating up bits of organic debris, dust, etc. Slime molds are not an indication that something is wrong at all, and no remedies are recommended. It will soon disappear on its own.

I have the same problem, and with calamondin, I am sure this is not due to sunburn, I have been growing calamondin, kumquat and other citrus for many years and this is the first year that problems occur. At first, I thought that birds tried to eat the fruits but they are sour inside and so birds don't want to finish, I plan to go to the information desk of Teas nursery to ask, I would appreciate if any of you could help. K

It does look like one of the Lysurus, but it’s a bit too far gone for me to specify.