We own a Japanese Lilac tree and the center of the tree keeps losing all it's leaves. It seems to flower in the spring like it is supposed to but for the last two to three years there is no foliage except on the outer most ends of the branches. I hope it is not vercillium (sp?) wilt, and have attached some pictures that may help you in your diagnosis. We have had several trees in our yard die very unexpectedly over the years and I hope that is not indicative of some sort of fungi or other disease in our soil. We have lost a Magnolia, a Red Bud, and a Dogwood all of which died very suddenly over the last few years. We planted a beautiful Sugar Maple a few years ago and it too is starting to show signs of a problem on some leaves on certain branches. The Lilac leaves sometimes brown and curl up and drop off, but primarily it simply does not "leaf out' in the center of the tree and remains that way for the entire season. Any insight as to what we should do??