Does it look like an insect has nibbled the petals before it opened? They did mine last year.

I wonder if it could be aster yellows — a disease caused by leaf hoppers that shows up as weirdly distorted flowers.

I suspect a nutrient deficiency, although the aforementioned Aster Yellows is a possibility.

@Oakley That's a good way to describe the effect of whatever's happening, though there doesn't appear to be any insect activity on or around the buds. Here's another one, looking clean as a whistle.

Maria, I'm on the pc and enlarged the picture when I clicked on it. Those little stem thingys, looking closely the tips are all uneven, like something ate it. I never found my culprit either. I did buy some insecticide soap from Amazon the other day, so I'm ready. lol

Did you open it to see if anything is inside?

@zen_man I am not too savvy with fertilizers, so it wouldn't surprise me if there's a nutrient deficiency. However, I'm also intrigued by @party_music50 's suggestion of aster yellows. I had to look that up and now I think it might explain a few things.

One thing that was mentioned is that AY affects carrots, including producing a fuzzy mass of roots. I don't have a picture of it, but earlier this year when I pulled the lone carrot that grew, I was surprised by the roots. I had a couple stragglers still in the ground so I pulled them up today. I don't remember exactly how long they've been in the ground but the tops were really quite long (about 14"). This picture shows the carrots didn't even make it to two inches (they were Danvers, which are supposed to grow to 6-7").

I didn't see dill weed mentioned as a victim of aster yellows, but as it's related to carrots (I think?) that might also explain my strange dill. Several months ago I grew some dill that got quite tall and healthy looking, though it didn't have a very strong scent. Then, about the time it bore a few flowers, some of the new fronds didn't uncurl as they should have. I got rid of it right after that because it didn't seem healthy.

Hi Maria,

Those stunted carrot roots strongly suggest Aster Yellows. It can infect a wide variety of plants, and your Dill would also be suspect. I will see if I can find a complete list of plants that Aster Yellows can infect. I think it can infect well over 100 different plant species. I know from past experience that it can infect my zinnias. It is spread by a particular species of Leafhopper. The infecting organism is VERY weird.

ZM

I strongly suspect herbicide drift. some plants are so prone to herbicide that all it takes in opening a can of the concentrate near them to cause strange things to happen.

If it's aster yellows why not on all the flowers on one plant?

LindaC, it's caused by leaf hoppers, and, afaik, only the buds that have been infected get weird.

According to this, cosmos are susceptible to aster yellows:

https://homeguides.sfgate.com/common-diseases-cosmos-flowers-65510.html

@zen_man Thanks for the info, and for trying to find a complete list. I'm very curious if AY also affects mint. Something's causing the leaves to curl strangely, but it could well be something else entirely.

When you say you disposed of your infected plants as if they were contaminants, what exactly did you do? I'm guessing don't put them with yard waste, for starters?

@party_music50 Thanks for that link. "Remove and burn infected plants promptly"--yikes! I have a very small garden bed (I'm guessing 6' x 12'), next to a small "lawn" that is at least half weeds. If the leaf hoppers are hiding out among my weeds, I'm afraid I'm doomed!

Hi Maria,

So far no luck finding an actual plant list of plants affected by Aster Yellows, but the number of affected plant species has increased from the commonly quoted 300 to 350, according to this link:

Aster yellows is caused by the aster yellows phytoplasma, a bacterium-like microorganism. The disease has an extremely diverse host list, affecting more than 350 species in 54 plant families. The phytoplasma is vectored by several species of leafhoppers (Family Cicadellidae); primarily Macrosteles quadrilineatus (formerly M. fascifrons) in North America.

" When you say you disposed of your infected plants as if they were contaminants, what exactly did you do? I'm guessing don't put them with yard waste, for starters? "

I sort of did, but I double wrapped them in a plastic bag inside a plastic bag, which was then included in a larger plastic trash bag that went directly to a commercial landfill. And I washed my hands. I don't know if there are any "official" instructions on what to do with Aster yellows infected plants. A large-scale infection could be problematic.

ZM

@zen_man I found two items of interest. First, How to Identify, Treat, and Prevent Aster Yellows (TheSpruce.com) explains that as long as the plant is living, it can carry the disease. Once dead, though, it's no longer infectious and can be composted. I know The Spruce isn't a science journal so I might verify that elsewhere.

Second, when searches for "aster yellows plants list" etc kept coming up short I found the scientific name and googled that. Bingo! Looks like a pretty extensive list here; also info on where it is found (including which US states). Candidatus Phytoplasma asteris (yellow disease phytoplasmas) fromCABI's Invasive Species Compendium (CABI = Centre for Agriculture and Bioscience International)

Another document fromWisconsin Master Gardener, that includes a list of common plants (with their common names). This is interesting: "High temperatures (88°F for 10 to 12 days) inactivate the pathogen in insect vectors and plants, so the disease is rare or absent in hot areas of the world, and is reduced during hot spells." Hmmm...Well, I might not have to worry too much longer. Hahahaha!

Hello Maria,

Bingo! There is a decent list of susceptible plants in the CABI list. As I am sure you noticed, Cosmos is in the list. And Zinnias are the last entry. I am not sure that hot spell thing helps me yet, but I have had Aster Yellows on only two zinnias in my total experience. So I don't consider it to be a problem. Although that is a scary life form that causes it.

ZM

"University of Illinois -- Report on Aster yellows" with text and images -- https://ipm.illinois.edu/diseases/rpds/903.pdf

Hello Jean,

Thank you very much for that link on Aster Yellows. The included Table of A partial list of plants susceptible to the aster yellows bacterium for Vegetables, Ornamentals, and Field Crops and Weeds is one thing we were looking for. That is an excellent reference on Aster Yellows. You are a very capable finder of information on the Web. That is a very valuable talent in these modern times. Thanks again.

ZM

So now I'm on the hunt for anything suspicious. This yellow zinnia plant looks healthy enough, but what's up with the flower? Pink zinnia for comparison.