dying roses

mid central, FL(Zone 9a)

my sister sent me these three pictures of her neighbor's Knockout Roses. she wanted my opinion on the problem but i would like to hear from people on this forum before i talk to her again.
the roses are in st.louis, missouri. they have had a lot of rain, a very mild winter by their standards, cool temps then really hot ones interspersed. my sister says there are no webs or evidence of spider mites or any other pest. i'm leaning towards some kind of fireblight but i really just don't know.
any comments are appreciated.

Thumbnail by trackinsand Thumbnail by trackinsand Thumbnail by trackinsand
Richmond, TX

Oh my! I have no clue. Looks like sudden death whatever it is! Do they have gophers? (Actually it does not look like gopher damage - they aren't wilting first.)

mid central, FL(Zone 9a)

no gophers.
i did talk to her and i told her to prune them almost to the ground and then clean her tools and get rid of all the trimmings. without seeing them in person, i'm really at a loss.

Long Beach, CA(Zone 10a)

Just found this thread so I'm throwing in my two cents worth of ideas.
Three things come to mind, but not in any specific order:
1.) Possible damage from overspray from a weed killer like Roundup ???

2.) Fertilizer burn ??? (Too much nitrogen ???) Am leaning towards this one.

3.) You mentioned they had a lot of rain and then heat spells alternately...I've had that happen when it's been really rainy and then a week or more of heat...the new growth (or all of it for that matter) seems to burn up due to the extremes.

Like I said, just my two cents worth.

mid central, FL(Zone 9a)

thanks, jd. i haven't talked to my sister recently to see what's going on with them. i'll find out more today and see if any of your ideas could apply.
:-)

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