I have a 6 foot lilac bush. Its leaves have wilted this fall. It had bloomed beautifully this spring with no concerns. Now that it is fall, however, the leaves have wilted and I was wondering if there is a fertilizer I should use before winter. Or is it a grub of some sort that is affecting the bush? I did check the roots and could not find signs of mice or moles around the bottom. Your help would be greatly appreciated.