Several of my daylilies have developed these whitish spots on the foliage. All the affected plants are in the same bed. It is not rust. Any ideas as to what it is?

I took this photo just the other day. Slug on 'My Heat Belongs to Daddy':

So it is probably slug damage? I thought they just damaged the blooms. Time for some slug bait.

Good to know. I didn't know they did this!

Oh, totally, I have a lot of slug damage on the leaves.

@DeweyRooter Sometimes hard to tell from a picture but it doesn't look to me as though the surface of the leaves has been eaten off as a slug would. There are brown edges to the spots and darker centres as well so I would think a pathogen of some kind, or is it possible that some substance was splashed on the leaves? Pat might have some insight @Hortaholic

I guess it is possible that something was spashed on the leaves, though I don't know what. The plants in that bed are planted around my mailbox, so they are right next to the road. They don't use salt or anything on the roads here, but there are trucks going by all the time and of course the mail truck stops there every day. Could be.

When I started the thread, I was assuming that the spots were caused by a pathogen. The plants seem OK otherwise and several have scapes.

@DeweyRooter Pathogen was my first thought too, especially given the apparent dark area in the middle, but just to rule out other possibilities might the municipality use herbicides on the road?

Yes, it's possible though I have never noticed a truck spraying the roadsides in our neighborhood.

Thinking along the vehicle line, all the commercial lawn people are out. The ones that spray herbicides and such. Could be a few drops hit your foliage from a sprayer that was leaking as the truck flew by........Maryl

That is quite possible. They go by here all the time.

DeweyRooter said: That is quite possible. They go by here all the time.

Key maybe whether it spreads to the daylilies away from the road, in which case it would be a good idea to investigate further.

I am definitely watching for further spread. So far I haven't seen it. Next time I walk in the neighborhood, I will look at other people's daylilies, too. There are one or two folks who have some growing close to the road.