I'm having issues with one of my large beds that runs the length of my property that is currently planted with english ivy, sweet woodruff, bee balm, lilacs, peonies, roses, elderberry, and ninebark. I think that the soil might be infected with Phytophthora, Rhizoctonia, or Armillaria, and causing root rot and massive die-offs. First to go was a prized rose, that had gotten huge and had the best display, the following year (last year) it just died, almost suddenly. At first I thought that the ivy was choking it, or the bindweed that I keep fighting to eradicate, but then the peonies didn't come up this year, I've had them for years. Also this year, the lilac is showing serious signs of stress and die-off. Branch-by-branch are dying at the bases, no obvious insect damage, a little powdery mildew, and the same with the ninebark (next to the lilac). (We had been following the cut a little every year to rejuvenate it as it was very tall and leggy) The soil is not overly wet, and this location is in full sun. I'm worried that the soil might be infected, and wanted to see if there is a way to tell, and if it is, a way to remediate the soil without removing all the plants. The only amendments that I have added to the bed is an occasional compost tea, and in anything I have planted I have added a few scoops of compost when planting. Thanks!
To find out for sure you will either have to dig out some dead or dying roots and identify the offending organism or submit a soil sample to a qualified lab that can do a biological assay. If it is a fungal pathogen then you can use things like copper based fungicides or find other microbes that will predate the offending organism. For pretty much any pathogen there are commercially available 'enemies' that can be purchased and applied.
Just a hunch, but have them test the plants for Phytophthora ramorum (Sudden oak death pathogen) which is a relative new-comer to the NE of the US but affects many woody orrnamentals.....could be something else as well including a different Phytophthora.
Thank you for all the replies, I will contact the extension. Hopefully they will be able to shed some light on what I'm up against. It is a shame, the monetary loss is not large, but many of these plants have been with me a long time now. I'm not sure what is worse, all that I brought to this bed, or the lilac that may have been here since the 1920-1930s. I'm only the third owner of this house, and that lilac had been here long before the longest living neighbor moved in (+ 40 yrs ago).
I carry this gun in case a vending machine doesn't give me my fritos. This gun and this tiny ad: