Elderberries require well draining, moist soil and full sunlight. In this hot, dry weather it could be wilting because it needs more water. Be sure to check daily that the soil is staying moist, but not overly wet. It's also a good idea to mulch under the bush to slow down water evaporation from the soil.
There are also a number of diseases and insects that prey on elderberries. I suggest you check the woody parts carefully to see if there is any damage to the bark, or if you see any cankers. Check under the leaves for sucking insects. At the following website, you will find a list of diseases and insects that affect the elderberry. If you have bark damage, I suggest you take a sample to the Plant Clinic at 869 Hanley Rd. in Central Point, between 10am and 2pm. Check this website for more detailed descriptions of the diseases and pests.
http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/elderberry.html
 

Hello Sharon,
Thanks for the quick response.
Water is not the issue. The other plants in the area are doing fine and the soil is nice and moist, not saturated.
Doesn't appear to have cankers (don't know if I'd recognize cankers on an elderberry), no insects (visible, chew or droppings). The leaves, plant-wide just crumble when crushed. Also purple blotches on leaves. Attaching photos.
May try the Pant Clinic - thanks.
Much appreciated,
- Stewart

It looks to me like the fungal disease verticillium wilt, to which elderberries are susceptible. It affects whole branches with wilting such as seen in your picture of the foliage.
I picked up the following information from the Missouri Botanical Society.
"Symptoms of verticillium wilt.. might include sudden wilting of small branches, yellowing of foliage, stunting of growth and premature defoliation. Sapwood of infected branches typically has olive-green to black streaks."

Fungicides will not do any good, but proper sanitation procedures may help. Again, from the Botanical Garden:

"1. Sanitation. (P)rune damaged areas of trees and shrubs. Pruning disease-damaged branches and foliage plus increasing the vigor of trees and shrubs may help to keep symptoms checked. Be sure to sterilize pruners between cuts.

2. Plant resistant or tolerant species. This is the best way to manage this disease. Fungicides are not generally effective or practical."

You can access the site through this link: http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advi...

To confirm my diagnosis, I suggest you cut off a portion of an affected branch and take it into the plant clinic.

Thanks for using Ask an Expert.

Thanks Sharon.