here in my z5.. the lilacs are just finishing bloom.. it is the ONLY time to cut them down ... if you have any dream of flower next season ... if you dont care about bloom.. cut them any time ... but.. when it all boils down ... its improperly planted ... too close to the deck.. get rid of it ... link below to what lilacs can do, when healthy .... basically swallow that deck cut it back to about 3 foot spikes.. and just start digging about 2 feet out from the stump .. using the spikes to wiggle and find the major roots.. couple hours of good exercise.. and you will be all set ... its simply not worth the effort to rejuvenate a mis-planted plant ... ken Here is a link that might be useful: link

I do not recognize this so I Googled it. This might be helpful https://www.google.com/search?q=black+spots+citrus+leaves&biw=1680&bih=857&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjYltv_39nQAhXCRSYKHXBhDDIQ_AUIBigB#imgrc=3GynaX0KoECnTM%3A

Hmm...that looks like what I thought was black citrus aphids on my Ponkan which I wrote about in another post. It is strange how it keeps going after that one tree. I keep spraying and cleaning it off with oil spray or soapy spray but it keeps reappearing. I hope it does not spread to my other trees. The new leaves are beginning to harden up on the tree now so I hope the bug will soon give up on it, but also am afraid it will start looking at the new growrh on my other trees. I treat them all with the sprays. I can't figure out where they are coming from as I don't see any ants nor what about it that attracts them to that particular tree. I have another Ponkan at the other end of the greenhouse and so far that is not attracting them. I think maybe that is because that tree gets a lot of air movement as it is nearer a fan. I keep suspecting my hibiscus may be the host as I usually keep them away from my other plants as they are notorious bug magnets, but even they seem bug free so far and not near this particular tree. Maybe they are in the soil of that particular tree, but I have even drenched the soil and I am still getting the black aphid or black fly back for now about 2 months. It is interesting to me that it likes that particular tree. Cory

Pesticide injury is a possibility and a virus disease or ethylene gas injury can also be to blame. Usually look at the specific locations within the greenhouse to pinpoint the problem. How widespread is the damage? You mentioned 2 varieties. Do you have other varieties that are not affected? I heat with wood stoves and surprisingly the newer hybrids Torero and Rebelski are first varieties to exhibit intolerance to the stove gases. I would suggest taking a sample to your nearest university plant pathology department. Your county extension service can make the connections for you.