trees are turning black

Asked September 6, 2016, 10:23 PM EDT

We've had two magnolias turn black and die. First the leaves started to turn brown/black, then noticed the branches (extremities) turn black. This continued working its way back to the trunk until the entire tree died. One magnolia was about three years old, the other was more like 10 years old. Now we have a curly-branched willow tree doing the same thing (it's was planted last fall). The magnolias died in the spring and the curly-branched willow started turning about 6 weeks ago. Pictures of the willow attached. Please help.

Benton County Oregon magnolia plant health willow horticulture

1 Response

Hi, thanks for using E- extension. We cannot be positive about diagnosis based on pictures, but one disease that fits this situation is Phytopthora root rot, which many woody ornamentals are susceptible to. You could use the plant disease diagnostic clinic here at Oregon State (costs $60), or, you could try planting something that is NOT susceptible to Phytopthora. Be aware that this disease can travel in water, and can stay in the soil and plant debris for a pretty long time. Phytopthora is especially suited to areas that stay too wet, too long, so make sure you are not over-watering in this area. The first two links are info about phytopthora- the last is to a list of plants that are NOT susceptible, that you might want to try. Please don't hesitate to follow up if reading the Phytopthora info does not match your situation or if you need more info.
http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/phytophthora-root-rot-on-woody-ornamentals

http://www.agrisk.umn.edu/cache/ARL01696.htm

resistant plants:
http://extension.udel.edu/blog/phytophthora-resistant-plants-for-the-landscape/

Hope you find this helpful, Nicole