Hi Lin, Sounds you like you have done a lot to try to save your basil. Speaking for myself I am a bit confused by your post, especially with the timeline. When did you move to the place you live when you started putting your basil plants outside? Did you move them back inside after that? You say they have been ravaged since yesterday afternoon--is this when it all started or since you moved them back inside? Also helpful would be... to know where you live and if you have a photo of the plants.

I moved about a month ago, and started keeping the basil on the porch. I don't remember at what point I started noticing damage, it was slight at first and got progressively worse. About 4 days ago, I brought most of the basil back indoors in a weak attempt. Didn't help, it was still being chewed up. About the day before I brought it indoors was when I started spraying with the soap and cayenne pepper spray. A couple days later I added the D.E. Yesterday I flooded the pots to try and kill any insects living in the soil (I placed them in a big cooking pot, and filled them up as much as possible, pouring the water into the pots until it had drained out so much the line was up to the top of the pot. Left it alone 5-10 minutes, then pulled them out to drain). I hoped that would do it. But instead, today, the basil has been even more ravaged than any other 24 hour period.

I live in Indianapolis IN. These photos are some of the damage from yesterday to today.

http://i38.photobucket.com/albums/e103/Lin_171/20150610_145303_zpsqi6mr6ng.jpg

http://i38.photobucket.com/albums/e103/Lin_171/20150610_145336_zpsczdq6vol.jpg

http://i38.photobucket.com/albums/e103/Lin_171/20150610_145410_zpswj2xh367.jpg

Everything was thriving before at my previous place, but i don't have the indoor sun I had there. I bought another small basil plant a couple days ago because of the damage to mine (including leaves at the bottom being weak and yellow) and I'm also terrified that will go the same way. I've got 3 basil plants in pots (around 12" tall, not very busy) that are being badly attacked. I've got some clones that are thriving, and were being left alone but now starting to be eaten since I left them outside and brought the big plants in. So i think they prefer the more mature leaves (I do notice most of the damage higher up)

I put many months and tons of work into this basil :(

I hope someone with more confidence or experience will pipe up. Based on the damage and how you have not witnessed a bug on the plant, I'm guessing the culprit is a slug. But I would carefully look at the leaves on both sides and stems for green caterpillars also. If you can pinch off the bugs in the act, that would be ideal.

Not much we can say to help without the bug id. I've never heard of flooding a pot to try and rid bugs. To me sounds like it would just create overwet soil and invite fungus gnats, but those don't gnaw leaves.

The soap spray will only kill certain bugs that it coats--the cayenne may repel, a little, but I've never tried. DE is good for only certain types of bugs and useless once wet. If it may be slugs, look up either copper collars or beer traps.

The cayenne is supposed to keep bugs from chewing the leaves (due to taste) and the soap and DE kill soft bodied insects. I'm trying to catch something in the act, since it seems the damage is done overnight. I check them many times during the day and rarely see anything on them. But haven't found anything at night either, I read to check after 10pm. For example its 1am right now and I just checked the indoor ones. Didn't check the current outdoor one (has a couple leaves with tiny holes, not the severe damage with the ones I've brought inside) Its difficult for me to check on them at night though.

The flooding was recommended because it said the beetles can live in the soil (which seemed to make sense since the plants are still being eaten since taken indoors). It said doing so would drown any beetles living in the soil. And when I did find one and squished it, it was in the soil when I was bringing them indoors and checking them out.

How could slugs be getting into the basil indoors? I'm not aware of them being able to live in the pot in the soil?

Lin, I am not a huge slug expert or even know if you have a slug problem. But apparently they can hide in the soil and enjoying a meal of tender roots. Slugs do like to come out at night because they are so moist and weird. And cloudly, rainy days.

and they could survive the drowning? i do think at least part is earwigs, found a bunch bringing my one basil that was outdoors in for the night. knocked one off and found a hole where it had been

pretty sure the damage is from earwigs. i squished 2 on my basil this morning. i set traps last night but they were empty. unsurprising because the directions were to set on the ground or bury in the ground (like water or oil traps in containers). i put toilet paper rolls stuffed with wet toilet paper on the pots, and the others next to the pots. added more D.E. before bed, maybe why I caught 2 this morning. I'll try a borax and oatmeal bait tonight too but im getting at wits end. Here is 24 hours worth of ruined leaves:

http://i38.photobucket.com/albums/e103/Lin_171/20150612_170648_zpsgucmwckg.jpg

well since i had to figure it out on my own, I thought Id report back on whats finally working for others in the future.

I started with soap spray with cayenne pepper, didnt help the large damage but did help the tiny holes.

Next I added diatomaceous earth (de) to the soil at night. since the soil is so moist, by morning it would be wet and useless against insects.

I flooded the pots to kill as many things living in the soil as possible, and started keeping them inside.

At this point I was still getting extreme damage, losing about a half cup of leaves a day from just 3 small plants.

I tried earwig traps, an oil trap, soapy water with oil around the inside rim trap, and wet newspaper traps. I only ever killed 3 earwigs total with these (this is indoors) while still getting tons of damage.

Next I set up earwig bait, oatmeal and borax, and instead of putting de in the soil dusted the leaves with it. I set up the bait on its own, and put some on top of the soil for anything coming out of it. The next morning I had almost NO damage. I think because they ate the oatmeal bait instead of leaves. I used ground up oatmeal i had leftover from making colloidal oatmeal and sifting out the pieces. After a few days of this and getting NO damage finally, Ive started putting my basil outside during the day. I keep the leaves dusted with de (i use food grade de, I feed it to my pets) and place borax traps nearby but not so close to encourage insects into my basil. Im getting slight damage, but its going to have to be the toss off for bringing the plants back outside where they get the sun they need. I put them out in the morning and bring them back in around 7 pm to stick in the windows. This is so its well before the earwigs come out of hiding for the evening and night meals.

It's a good bet you're missing a chewing pest, perhaps slug or caterpillar. (I vote for the latter.) You'll need to look day and night; you must look very closely because some cats are the same color as the leaves.

Further, I would leave the partially chewed leaves on the plant; some pests return to the scene to continue feeding. (Removing the partially eaten leaves from the plant is doing more damage than the pest, whatever it is.)

Thanks for replying. But if you read the last post you can see that I've cured the problem which was earwigs. Since then I've also talked to neighbors about what a problem the are in the area.