I have 4 knockout and 6 double knockout roses. Last year we had some kind of pest or something on the roses- ate the leaves right off the stems. I fought this last half of the summer and fall. This spring I have not one rose that is alive. Can I replant in this spot or do I need to worry about the soil being contaminated. What to do? Please help!
Knockout Rose Pests
You should be able to plant some new roses in that spot. I would change out the soils for a good 20 inch diameter area where each rose is to be planted, using some good bagged garden soils mixed with some bagged top soil. If you could not ever seem to find what was doing the damage, I wonder if it was a caterpiller of some kind? Also could be deer or elk if you have those around where you are. Perhaps using a systemic insecticide is in order. I do not like to use those but this sounds like a significant problem. Maybe one treatment will be enough to send whatever it is packing. I do have to ask why you would think the soils are contaminated if something was eating the leaves off the roses? If it is because they died, that is likely due to the fact that they did not have enough foliage to store up enough energy to survive the winter time. So that would not be a problem of the soils. The reason I recommended changing out the soils is to get rid of any eggs or larvae in those soils. The systemic will take care of any that are missed.