Most likely you've got wasps who are using small parts to build things with. I'd bet if you go out when it's warm you will see them hanging out amongst the Rhubarb leaves.
My advice is to harvest the stalks and let them have the leaves.

Thank you Nativewines. My rhubarb is only in the first season so there's not much to harvest. Should I just let it be? I am surprised to see something eating the leaves because I was always told that they were poisonous.

Well, they're poisonous to humans, but apparently not to grasshoppers. At least I think that is what is eating mine. I have a second year plant that looks fine, but the rhubarb seedlings I planted out this spring have a good bit of damage. Maybe the oxalic acid content in the leaves increases as the plant gets bigger?

Hi Muddy,

I dont know if you have the same thing I did, but starting when I first planted my (little baby) rhubarb five years ago, something was gobbling down the leaves big time! It took me till the second year, when I found the hollyhocks planted right next to the rhubarb disappearing too, that I finally figured out it was earwigs! They were virtually defoliating the rhubarb plant, which by then had some full-size leaves, and it was hard to believe such tiny things could be doing so much damage, but when I started finding themÂeven in the daytimeÂcrawling around on the top of 5' hollyhocks, I was sure they were causing the damage. At that point I started sprinkling a granular soil insecticide around the base of the plants. ItÂs the stuff you get to spread on a lawn when insects in the soil are damaging the grass, and itÂs effective against a plethora of different insects. The first one I got was by Bayer, and I donÂt remember what it was called, but I got it because it was the cheapest one, and the bag said it worked for earwigs AND that it was safe to use around veggies. The more things I put in, the more damage I was findingÂbut the rhubarb was always the most damaged plant! Last year I switched to an Ortho one called MAX Insect Killer for Lawns. They both work well, but I think the Ortho granules seem to be easier to spread!

The first year I started spreading it around any plants where I was finding damage. The next year I discovered they had nests along the bottom of the wood privacy fence, the bottom of the railroad ties in the yard, and just about anywhere where they could get down between anything and the soilÂbut especially decaying wood. I started sprinkling the granules along the bottom of the fence, the railroad ties, and anywhere else where I was finding concentrations of themÂin addition to continuing to spread the granules around any plants showing damage. It took three years to get rid of enough of them that IÂm not noticing much plant damage anymore. The previous owners werenÂt gardeners, and apparently the earwigs had been proliferating, unnoticed, in the yard for years! Since I mulch everything, it creates perfect nesting areas for them, so I always keep an eye out for damageÂor places where I find concentrations of themÂand sprinkle a few of the granules in the area when necessary. The first two years I had to use quite a bit, especially around the hollyhocks and rhubarb (planted next to the shed and the fence), but now I use very little of it.

Since earwigs are out mostly at nite, you might want to wait till a couple hours after dark and go out with a flashlite to see if youÂre finding them on and under the plants. HereÂs are pictures of the damage they were doing to my rhubarb and Swiss chardÂthe second year after I started using the granules. It took two years before I could really see much improvement because I had so many of them to start with. In the beginning the damage on the rhubarb was WAY worse than what you see in this picture! Whole leaves were gone except for the veins! These pics were taken in summer of Â07. This year, finally, I have virtually no damage on the rhubarbÂand I havenÂt gotten any other veggies planted yet!!! But no damage on other perennials that were being badly damaged a couple years ago either.

IÂm also posting a link below that shows the damage from leaf cutter bees. They cut perfectly round little holes in plant leaves, and especially love rose leaves, but IÂve never seen them cutting rhubarb leaves.

I agree with Bonnie that grasshoppers could be doing the damage, but youÂd probably be seeing them on the plants if thatÂs what it was. If youÂre not seeing anything during the day, IÂd really suspect the earwigs.

Good luck. Let us know if you figure out for sure what it is.

Skybird

I found 1 very small, brown grasshopper, 1/4" long on a leaf. I put some "stuff" on it last night so hopefully he is no longer. I will keep you informed.

I get earwigs too, but fortunately not in large enough numbers to do real damage. But a couple of them came inside today on some lettuce and spinach I harvested. Ugh! They creep me out!

my rhubarb has been here for about 40 years. This year I found tiny, tiny black bugs all over it, even the new stalks just coming up. What do I do>

A picture would be very helpful.

If they are tiny, and very shiny, and jump really fast, they could be flea beetles.

I try to avoid using chemicals, so my first choice if they are causing a lot of damage, would be an insecticidal soap.

If they are those tiny, very shiny, jumping flea beetles:

I had good luck with Spinosad. This was the 1st year that I've used Spinosad for anything. I finished the rotenone/pyrethrin spraying flea beetles and I think it would have taken care of them after spraying a couple of weeks. But, turning to Spinosad seems to have put a stop to their damage.

I will start from the get-go with this spray next year. Those beetles can totally waste early plantings of brassicas. And, they do a fair amount of damage to the tomato plants. It wouldn't really surprise me if they chew on rhubarb, as well.

Steve

My rhubarb is getting eat'n up by something as well - there is hardly anything left of one leaf! I'm going to go out tonight as Skybird suggested and see if I see earwigs (I'm with you jnfr - they creep me out as well!!!). I'll try the insect granules, Skybird, and see if they do the trick for me (we grew chard last year and I definitely saw earwigs on them!).

Are the leaves of rhubarb poisonous to pets?! Hope not!!