Hi, 

We are not sure exactly what could be causing the die back. We don't notice any holes in the branches like from a wood boring insect. 

Did it receive any supplemental irrigation last summer with the drought? We can see the downspout in the back ground but maybe it doesn't get enough water to the root zone of the plant. A common disease to a lot of woody ornamental plants and one to hollies is Botryosphearia canker (page 2)which is a fungal disease.  It is a natural soil borne fungus and when there are extreme temperature changes or water changes, plants become stressed and the fungus moves in. It can form cankers in the branches that will girdle the flow of nutrients causing dieback. Many plants can live for awhile with this and if you prune out the dead wood and maintain irrigation in times of drought that can help prolong its like. 

Do you treat the lawn with any herbicide or pre-emergent? If so, do you know what product you use. Some herbicides can really affect tree and shrub health that is taken up by the roots that extend out into the lawn space. 

You can try to do a renewal pruning of the shrub, removing any visibly dead branches. It looks like there is some new growth coming closer to the bottom. If you trim out anything dead and take it back to where you see green stems, it could make a rebound. 

If you follow tips for lilac renewal pruning that will show you how. Various videos can be found on YouTube. Just try to search ones from a reputable source like a botanical garden, or university extension site. 

Emily

Hi:  Thank you for your advice and help.  We have pruned out all the dead branches and did notice some damage to some that looked like cankers.  We do have questions, please.

1.  Should we fertilize it now and with what, please?

2.  Should we paint or seal the ends of the branches which we trimmed or cut out?  What about the ones which we trimmed that show signs of green life?

3.  How often should it be watered?  It has been a fairly wet spring, but is there a measure we can use to determine when to water?

4.  Is it okay that we now have several very long, tall branches and some new growth at the bottom?  Should we prune the very tall ones, and if, so, when?

Thank you so much for your help.  We really appreciate it!!

Pat Grega

Fertilizer is not recommended. It is not medicine and can actually stress a plant further when it is struggling.
(Native plants like this also tend not to need much fertilizer- a couple of inches of compost would be fine and you could consider mulching your gardens with leaves that fall in autumn, which is a natural mulch option- just keep it pulled back a bit from the trunk/stems/crowns of plants.

No paint or sealant needed on cut stems or limbs of plants. Earlier generations did this regularly but it's been found that plants do better healing over without our assistance.
If you are seeing new sprouting leaves that is terrific!

As far as watering, these are plants that naturally grow in low swampy areas so they don't mind having wet 'feet', however once established they can be somewhat drought tolerant. Given that it seems to be struggling though, we'd recommend giving it a good slow drink if we don't get about an inch of rain a week, which can be measured with a rain gauge or by putting a tuna can out in the garden. (Dump them out regularly though as standing water can allow mosquito larvae to mature in it.)
As far as how to best water and make sure it is getting to the roots, here is our watering information: 
https://extension.umd.edu/resource/watering-trees-and-shrubs/
It's o.k. to have some tall branches while it is also growing back from the base.
It looks like your mulch is not too deep (not more than about 3 inches) but pull it back from contact with the trunks, and keep an eye out for any gnawing damage from rodents around the base. If there is a completely dead trunk, you could give it an tug to see if it comes up easily.  Voles (not moles which only eat soil invertibrates like worms and grubs) can chew/eat plant parts from just below the ground, including woody trunks.)

It's a great sign that you have re-growth. Good luck.

Here is a page from Virginia Extension with more info about the plant: 
https://www.pubs.ext.vt.edu/2901/2901-1077/2901-1077.html#:~:text=For%20increased%20fruiting%2C%20prune%20in,pay%20dividends%20in%20future%20years.


Christine