Penstemon - Red Spots

Orland Park, IL(Zone 5b)

I have red spots on my pentemon (Dark Tower) that seem to have popped up overnight. Any ideas, guys? Thanks.

Thumbnail by keanl
Ayrshire Scotland, United Kingdom

At first I thought of a disease called Rust and as the name suggests, it is orange/red colour but normally a powdery coating and it is much more evident that what you show,
Looking at some of the spots on the foliage it looks like a little bug that either sucks the foliage OR makes a tiny hole in the foliage and lays an egg and the resulting red mark is the grub laid between layers of leaf foliage, it then eats away the leaf.

IF you can, remove one of the damaged leaves, take it over a sheet of kitchen paper and try either cut through a red dot or use a really sharp knife the lift the scale out and separate it to see what's held within the little red circle. that may give you a better clue as to what you are trying to rid the plant with.
There will be lot's of sprays or whatever that can help but, if you dont know what exactly it is then you could buy several sprays and still have a problem.
It may be that at the end of the day all you need do is remove the damaged foliage and burn it or just leave it alone as there is no REAL problem but until you know by elimination you cant try anything.
Hope this is helpful. Best regards. WeeNel.

Orland Park, IL(Zone 5b)

Thanks, WeeNel.
I tried cutting into the spots and could not tell what they were. I took some addition views of the underside. Maybe that will help with the id. It has spread to a large number of leaves.

Thumbnail by keanl Thumbnail by keanl Thumbnail by keanl
Orland Park, IL(Zone 5b)

I think this is rust and I have treated plant with a fungicide. Hope this works.

Prairieville, LA(Zone 9a)

Keanl, leafspot is a pretty common disorder among Penstemon, either Cercospora or Septoria spp. a good fungicide is the treatment for it, the same as treating for rust.

Orland Park, IL(Zone 5b)

Thanks. I have had this plant for 2 years and have successfully fought off aphids. This year it really got big. These spots were a real surprise because they popped up so fast. I will add these links to my plant database.

Prairieville, LA(Zone 9a)

You are most welcome.

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