Sun burn. Or maybe a bacterial infestation.

why are the leaves wet???.. just rain??

if you are relying on lawn irrigation.. to water large-ish shrub transplants.. you might not be getting enough water.. deep into the root mass planted ...

could we see a pic of the larger planting???

i also note .. only one leaf in the pic is affected.. if it were me.. i would probably cut it off.. out sight.. outta mind .. though surely.. asking about it doesnt hurt.. knowledge is power ...

ken

Hi. Yes, that was some rain on the leaves. They are all on a drip irrigation system that delivers about 1 gallon per hour, 3 times a week. Is this enough? Of course they get any rainfall in addition to this. I planted them in November 2019. They were 1 gallon pots them. They've grown a lot already, about 2-3 ft high and wide now.

My first thought was sun burn, but these plants are all over the area where I live, and I've not seen this type of damage.

Yes, the photo is just of one leaf, but each plant has 10-20 leaves damaged and there are 12 plants. I can cut them all off, but wanted to check if there was something more systemic at risk that I need to address.

I've added some more photos to hopefully make it easier to work out what the problem is....

Thank you

Found this online . . .

Rust If the spots on your viburnum leaves are more rust-colored than brown, the plants may have a rust infection. This is also caused by various fungi. Viburnum leaves infected by rust will wither and die. This is a contagious disease, so you’ll want to destroy diseased plants in the spring before new growth starts.

Read more at Gardening Know How: Brown Viburnum Leaves: Why Leaves Turn Brown On Viburnum https://www.gardeningknowhow.com/ornamental/shrubs/viburnum/brown-viburnum-leaves.htm

Rust on plants usually appears as spots or powder.

Hi. Did you ever solve this problem? We have exactly the same issue and I’m not sure what to do about it! The leaves are rapidly going brown in patches then eventually shrivelling and falling off. Any advice most welcome!!

Hi. Yes I did. It was thrips. Much as I hate spraying plants, I ended up doing this once to get it under control. Seems to have greatly improved but I will need to keep an eye on it when the growing season starts again in a few months. By the time i'd pruned away the affected sections I'd lost most of this years growth.

Yes. How did you discover it was thrips? I have had the same problem that started last year and finally after war with my hedges they started coming back to life. This spring I didn't have any flowering on mine, but they were so nice and healthy, then again, just 3 weeks ago started with the same leaf rust going on. In battle again.

What did you treat yours with?

I asked the guy who treats our lawn. He pulled off a few of the newer leaves and turned them over. Showed me the thrips. I had him spray them so I don't know what was used. But it got rid of them and the new growth has replaced the old rusty ones. Sorry I can't help more with what they used.

I had this same issue and took some samples in to be tested at the UF/IFAS extension office. They sent it off to be tested and it came back as downy mildew. The agent was surprised too. I sprayed with mancozeb and the problem was resolved with one treatment, as the new leaves grew out beautifully.

Good to know. The company 'Evergreen' spray for a variety of things so perhaps it was the same for me. There were definintely thrips all over it though....

Of my 11 Viburnum plants, 2 each fall have leaf problems, but can't find photos of the problem to match. The outside edges of the entire leaf turn a rusty reddish color that spreads and these plants leaves fall off more quickly. I have used a copper fungicide now the past two years from late summer to early fall, but that hasn't helped at all. Any help would be greatly appreciated!