Look at the underside of the leaves for tiny caterpillars.

Try using Repel-All. I spray it on my freesias in the fall to stop rabbits from eating them.

Rain or sprinklers won't wash it off. The plant absorbs it, only have to spray new growth. It also comes in granuals.

Thanks! I still don’t know. I will try to look at night. i saw earwigs but I was told they usually don’t eat leaves. I suspect it might be caterpillars too.

what about cutworm damage .. thats the usual suggestion when something is felled like a tree .. and then just left there ...

plz add your big city location in every post.. you might be surprised how often it makes a difference ...

most of us would prefer you ID a problem.. before reacting with products ... just to be on the safe side ... that said.. it never hurts to decimate the slug population in spring.. rather than wait until there are a billion of them in august ...

btw: cutworms turn into other things and disappear from the soil rather quickly ... depending on where you are ... so it may already be too late to do anything about them .. other than plant more plants ...

ken

https://duckduckgo.com/?t=ffcm&q=cutworm+damage&iax=images&ia=images

Hello S. Wang,

"I saw earwigs but I was told they usually don’t eat leaves. "

Earwigs do eat zinnia leaves, as well as zinnia flower parts. Earwigs feed at night. And your photo shows classic earwig damage to zinnia leaves. The mulch you have is a favorite environment for earwigs. Snail and slug poison is not attractive to earwigs, or effective against them.

Years ago, when I applied a heavy mulch to my zinnias, they were eaten up with a lacework pattern of uneaten veins, and I went out at night with a good flashlight and discovered my zinnias were covered with earwigs. I examined the mulch the next morning, and found it to be full of earwigs taking shelter under and in it. So I removed the organic mulch (I had applied a lot of it) and replaced it with a river sand mulch, and no more earwig problems. In my opinion, your organic mulch is simply incompatible with zinnias because of earwigs. Such a mulch is also conducive to Pillbugs, which can also become numerous and do similar damage to zinnias.

ZM

Thank you. I have to do the flashlight At night. But this mulch is all over my yard. Ug. I will make a pint of doing it tonight

One way to see if it is earwigs... roll up a small piece of wet newspaper and put it near the plant. Unroll it in the morning and see what is hiding in there.

-Babka

Thanks everyone. i was just out there with my flashlight and you were right. it is definitely the earwigs. Ug! I used this mulch all over the yard. i will try to remove it as much as i can around the problem plants but i cant get it all out of the whole yard. do you think the wet newspaper would attract the earwigs to go into them instead of eating my plants? Is there anything to fight earwigs?

Hello S. Wang,

" ...you were right. it is definitely the earwigs. Ug! I used this mulch all over the yard. "

Years ago, I had mulched my entire zinnia garden with organic leaf mold to a depth of well over an inch. Functionally it was good mulch and protected my zinnia root systems from overheating in the full sun, it conserved soil moisture, and it prevented weed growth. But, as I discovered with a flashlight, it harbored earwigs and pillbugs in scary numbers. The mulch was fairly easy to rake up onto a snow shovel, so my question was, what to do with it? I had an 8-foot in diameter wire-enclosed compost pile, so the mulch went into it for further decomposition. That project took several days. I had heard of farmers using a "dust mulch", so I purchased a truckload of washed river sand and mulched my zinnias with clean sand to a depth of one inch or more. I have since moved from that location (in central rural Maine) to where I am now (east-central rural Kansas). I now consider sand to be a requisite to my gardening, for use as a mulch and as a soil conditioner. And to prevent tracking in mud from the garden. I purchase sand by the 20-ton truckload, because that costs much less per pound than by bags of play sand from a home store.

You could leave the organic mulch in place and bury it in an inch or so of sand. Earwigs are insects, so you could go after them with one or more insecticides. There are systemic insecticides that enter the sap stream of the plant and make the whole plant poisonous, including the new growth of the plant after you applied the insecticides. I am not a fan of poisons, but I have used systemic insecticides out of necessity to control difficult insects like thrips on my indoor gardening zinnias.

It is not obvious what you should do next, but at least you have a better understanding of what is eating your zinnias.

ZM