Have you just brought them inside recently, or have they always been inside? The chewing with the scattered faeces in the first photo looks like thrips. The browning at the tip might be related, might not; no idea.

But the blackening shown in the second and fourth photos does not seem like a familiar sign of thrips or caterpillars. Was that there before you started spraying? If you're in North America, have you considered that four-lined plant bug that's supposed to be common on oregano?

Hi Sophie, thanks for replying.

The mint was outside all summer and it was very happy.

The oregano was purchased from a good local nursery 3 weeks ago. It has been outside for a few days.

Today, I just replanted both of them (because I wanted to see their roots). I noticed that in both the pots, there were some sow bugs (or pill bugs). I read that these guys are harmless...nonetheless, I did my best to make sure that there were none in the soil which they were about to receive.

I also noticed that there was massive amounts of root growth on the mint.

I have dealt with thrips before on my basil so I have some experience there but this damage with the translucent leaf and the black spots is new to me.

Please, any advice would be helpful.

Thank you.

Hopefully somebody familiar with thrips control can help. I'm pretty useless there, sorry; I don't really see much of them.

But, as a last resort: if you're planning on keeping the mint inside for winter, you could just cut it right down to the soil, bag the damaged stuff, and it will shoot right back up really nicely. Doing it outside means the pests will scatter out there, and you can keep inside tightly controlled.

Hi Sophie,

Do you mean cut the mint right down so there is nothing to infest and then bag the cuttings and throw them away right?

Update: I have now found these pests on my other mint plant which was perfectly healthy. Looks like they can jump or fly. What are these things?!?

I can't tell what they are from your picture. If you tap the leaves and they fly, you have white flies. Can you take a closer picture of just the white stuff?

Xiaobao,

Yeah. I can't see the whole plant, so you'd have to decide whether it's that bad. That new photo, the leaves look okay, except for the white stuff (honeydew maybe). I mean you could leave as much of the new growth as you want if you're sure there's nothing hiding in it. But both of those plants respond really well to heavy pruning and grow back really nicely.

If you were going to put it back outside, then it's not really worth it, because the bugs will just come back and attack the new growth. But if you're keeping it inside for the winter, then it'll get rid of the pests and you'll have a more controlled environment. Providing, of course, that there aren't any other plants in the room that might have thrips or whiteflies on them (doesn't matter about caterpillars).

For whiteflies though, I would just take the plant outside every now and then, ruffle the leaves or spray it with a hose to get the flies to disperse, and then bring it back inside. If you do that a few times, you should be rid of them.

Hi Sophie and zzackey,

Here are some complete pics:

a) Oregano - it use to be a lot more bushier.

b) baby mint - this one was extremely healthy but the pests have found their way to this plant and are starting to attack it.

c) mint - it looks devastated - I just pruned it back as I have found more leaves with the tiny wisps of webbing and black poop.

Hmmm.....any more thoughts from anybody?

I do think that I have spider mites.

I made a insecticide of 5 peppers, 2 garlic cloves, 1TB oil, 1 tsp dish soap and 4 cups water. I then mixed this concentrate 1:1 with water.

The spray has worked I believe! It's been a few days and I'm not seeing the webbing.

An update. I had to leave town for a couple of days. Before I left, I watered the plants heavily and put a metal bowl underneath the pot to catch the water. Upon my return tonight, look what I found in the water bowl of my mint and oregano (see pic). They were still alive!!!

Is it a millipede?

It looks like a worm from the photos, but if it has legs then yeah maybe it's a millipede. Whatever it is, I should it's probably harmless to your plants.

I saw OP's photos (1st one, showing leaf damage, and 3rd one showing little green worm), and they are very similar to the pest that devastated my herbs last summer.

Numerous varieties of mint, in large pots, and thyme and oregano in the ground. All outdoors, at Seattle, Washington. The culprit has been identified as a very small brownish-orange moth, 3/8 in. or so, with no name assignable at present. Frequent application of a standard-strength pyrethrin/butoxide formulation seemed to have little effect.

Looks like damage from a four-lined plant bug. I'm having the same issues with my oregano and sage right now.

Purple spots on arugula & oregano