I have a 4 year old Willow Hybrid that is dying. Last fall two trees were infected with Willow Scale. Treated with BioAdvanced 12 Month Tree and Shrub Protect & Feed Concentrate. In March they both seemed to be bouncing back with new healthy growth. Then 2 weeks ago one of the trees started to get brown leaves. I don't see anything obvious but would like to try and save this tree. Any advise or a direction I can follow to diagnose and treat before it's too late would be greatly appreciated. Thank you in advance.
Sorry @LIQUIDLIGHTLV didn't notice your post before today. Welcome to the 'Stew' I honestly think you did well to rescue at least one of your trees. If you were just fighting scale insects, that was difficult enough to overcome, but I think the problem could be that when your trees were vulnerable then, there was always a chance that some other problem might have hit them while they were down. I think there's a willow sawfly for example. You may need to remove that one, it's not looking good.
Time to remove the dead willow it will host other insects / diseases to invade the surviving willow. Dead wood from trees will send off a gas from infected wood which can affect trees near by. You could cut a sample of a stem from each tree and take it to the college extension horticulture service in your area. They can diagnose and identify treatment for the surviving tree. Also one could be root bound and not receiving water . You could dig around the root system to check for matted roots could strangle the main root feeder causing little nourishment or moisture for the tree to survive. In some cases underground mammals will also eat the roots during winter leaving the tree to die. Look for any suspicious mounds near by or small entry openings to the soil area around the trees.
