I have a Purple Robe Locust which is about 10 feet tall with a nice canopy. It's been in the ground for about 6 years and suddenly is having the leaves turning yellow-ish and then dying within a day or so. I see no leaf spots and I see no insects. This is alarming, to say the least. Any ideas? I'd hate to lose this one! I am in the Tacoma, WA area at about 600 feet elevation.
Hi, The suddenness of the tree's illness suggests an environmental stress. Check to see that the soil is not too dry (or wet). If you find that the soil is extremely dry, water the base of the tree on a slow trickle for a few hours; if the soil is too wet, do not water it for a couple of days. Also - try sheltering the tree from strong winds, as the bark is brittle and can damage easily. To check if it has a disease, cut a branch off and look for tell-tale signs of Verticillium wilt (click on the link for a picture). That being said - you still need to check if the tree is alive. To do this, scrape off some bark from the trunk to expose the plant tissue (you can use a small knife - the cut is less than an inch). Live tissue should look green/pale green and moist. Also, do this same test on the tree branches. Additionally, the branches should be able to flex when you bend them. Dead branches are very brittle, dry and will snap as soon as you try to bend them. If you think your tree is dead - it is up to you to call the proper authorities/arborists/park board to inspect or take down the tree. It is always unfortunate when such a lovely tree dies, however, Robinia is known for growing suckers or sucker sprouts. There is a chance that the root system may still be alive, and grow new sprouts that will form new trees. Do a closer inspection to see if there are any insects or disease symptoms in or around the tree. If any new developments or concerns arise - feel free to continue on this post. Good luck!
