I am definitely keeping an eye on it to see if that is it or not. Something occurred to me though.....we have only used our air conditioner once this season, and the warm air blows in the direction of (you guessed it) the sambucus. I am thinking that could be a probablility as well. DoH

There is some evidence that the systemic insecticides are contributing to the demise of the bees and other pollinators, so they may not be something you would want to use. For relatively small infestations of non flying insects such as Aphids the best means of control is simply a sharp spray of water. Alcohol used in many home remedy sprays is an antibacterial and does little to control insects, especially in the small amounts usually used. In amounts large enough to kill insects Alcohol will also kill your plants. Insecticidal Soaps are contact controls that once dry have no residual affect, but will harm beneficial insects as well as the pests. Keep in mind that any poison you spray in your garden has the potential to harm every beneficial insect as well as the ones you want to target.

Thank you all for your answers and sorry for taking so much time in coming back with more info! I took a few pictures which i hope will be more useful than the previous one. I fear this plant cumulates the issues. As you can guess from the pictures, this is an office plant and it probably doesn't get the needed TLC. I suppose it needs repotting. In fact it's not mine but I took care of it during it's owner's prolonged absence. It is next to a window and gets a bit of the soft office ventilation. I water it generously once a week. It has time to dry for the next watering. I don't put fertiliser, just plain water from the tap that I put in an open bottle the week before. I just pruned those ones: The leaves at the top and the bottom are the most beautiful ones. The ones in the middle are weak. Hopefully, you can see the larvae and flies: Can you hereby ID it? Another issue? Thanks again for your time!

I would absolutely expect to see the spores that high....and higher. Just be grateful that the mulch is not used any where near your home, vehicles, outdoor furniture, etc. They stick like superglue. As Jean says, these interesting little fungi are not harmful but are natural decomposers. Look them up and then investigate the mulch because you just might find some of the tiny little cups. They actively feed on dead wood....wood chips, old unpainted timber, and the like.