Question
Hello:
I live in St. Augustine, FL (northeast Atlantic coast zone 9). I have two Knockout roses that I planted 3 years ago. They look like one rose bush now. These roses have been prolific, hearty looking bloomers. I've never had a worry with these roses. Today is Monday, 5/10/10. During this past week on Thursday, 5/6, I noticed several new buds on one side of the roses that looked droopy or wilted. The rest of the rose plant had lots of fine blooms. The droopy part looked almost as if it needed water or their stems were broken but stems were fine. I saw no pests. Then the next day or two, more of the plant and all the blooms were wilted and droopy, and looked like they were dying. Now my entire Knock out rose looks dead. It looks as if someone sprayed weed killer on them. This has occurred in a matter of days. Not evan a full week. I asked my local garden center where I bought the roses and they asked if the damage or wilting was gradual. It was not, it was in a matter of days that I saw my rose bushes, leaves, buds, blooms all wilt, dry up and turn brown. Every leaf is dry as a bone. What could have happened? My local garden guy said he thinks chemicals damaged them. There are tons of Knock outs in my neighborhood and my neighbor's yards. They all look beautiful and blooming. Thank you.

Answer
When a rose starts to wilt it is usually caused  something has damaging or interfering with the roots. Rabbits, voles mice will eat rose roots. The other reason could be an insecticide if you used one. I get many questions that suggest Knock Out roses don't like insecticide sprays, especially the  three in one kind. There is a rare problem caused by verticillum wilt which causes roses to suddenly wilt and then die. And although you may not have used any sprays on the roses, a neighbour near by could have used  a herbicide of their lawn and the spray drifts a long way. Roses get lumps called cankers on their stems and this will cause them to wilt and die but I doubt all of your roses would have cankers on them. I would dig one up and look at the roots to see if there is any damage or even small black nodes on them. Hard to give an accurate answer as sometimes where you garden has a big effect because of the soil such as Florida.