I am sure its slug or snail. Almost overnite, they finish cucumber seedlings, okra and basil. Looks like basil is one of their favorite.

I had this problem last year, but not in raised beds, it was between cut worm, bunnies and probably cats. I had to start a lot of things over, only a few things survived the critter! I started using milk jugs until the plants got big enough, and it actually really helped alot for me! I had a great garden after that. And the plants seemed to grow faster and healthier under the jug without the cap. You can uncover them during the day if you think it is too hot, but I didn't. Hope you find a solution!

It can't be bunnies or cats, the bird netting works pretty well. Would I see the cut worms? I don't think we have snails here but slugs, yes, though I have not actually seen one in my veggies, I suppose it could be. They feed at night, right? So, beer traps? Under the straw or on top?

If it was a cutworm you would not have a stem left. Cutworms wrap themself around the stem and then bite it off leaving nothing but the root in the ground.

Alberta

I guess my money is on the slugs, then. Organic deterrents?
This may be a stoopid question, but if the stem is left, will it resprout leaves or shall I start over?

I would start over. Basil germinates quickly. As for the slug deterrent...save yourself some tuna fish cansm rinse them out and add beer or yeast with water to them, put the cans in your beds at ground level and in the morning you'll have a tuna can full of dead slugs. YUCKY I know, but the beer or yeast really works.
Empty can and repeat. This rain is really pulling all the slimey little creatures out here too.

How many slug bait cans would you use for a 4' x 13' bed? How far apart?

So I tried a test slug trap last night. I used yeast dissolved in water in a tuna can (I did not have any beer!). I put it in the area where the basil was, on the ground, edges slightly covered with straw. This morning there were no slugs in it. So either I did it wrong, or it is not a slug problem. Should I try it again with actual beer? Should the top of the can be level with the ground (sunken into the earth) or sitting on top? Any other thoughts/suggestions?

I have black plastic on the ground around my tomato plants and I have found several petrified slugs on the plastic - it must take them a while to cross the plastic, and they get caught in the hot sun when it hits the plastic?

Your problem is definitely slugs - think of slugs and snails as the same thing. Read the link below for more info or search for slugs.

Here is a link that might be useful: Best Kept Secret

I have the same thing happen with basil plants (cucs, so far, are ok). It seems to happen with the tiny, low-to-the-ground plants. Slugs would make sense; I have seen plenty of them in my garden. I have had good luck catching them with beer. I used a styrofoam cup and tore about the top half off, then dug a little hole in the dirt, stuck the cup in, and poured in the beer. I think the idea is that the slugs can crawl across the dirt directly into the beer-- so the top of the cup should be level with the dirt. I got plenty of drowned slugs. I think I used Miller Light, but I'm not sure. Make sure you use a container deep enough that the slugs can't crawl back out. A tuna can might be too shallow-- I'd vote for at least a couple of inches deep.

I tried the beer traps again last night, with real beer this time. Sunken into the ground, several spots in my raised beds. Although I dreamed about slugs, I did not catch any! Will leave it down for a while, maybe my slugs are slow witted? Maybe it's something else...

lolear
Sorry I didn't get back to you sooner, I had no computer, we had an electricl storm go through this area and I lost cable and phone service. I just got back online, but still have no phone service. Anyway, keep the tuna cans level with the ground, (sunken in the ground a bit so the top of the can (s) are level with your soil. If it is slugs, they will show up in the can with the beer. Don't know what area you are in, but I'm on Long Island, and we have had almost a full week of rain, so if its raining in your area, your beer is probably getting diluted.

Alberta

I've got something really chowing down on my basil, too. Don't think it's slugs, some of the plants are about a foot tall and the holes in the leaves are close to the top. Some leaves are about 1/2 gone. I don't want to use anything on them if I can avoid it. The whole point of growing my own was no pesticides! And why just the basil and not the oregano, tarragon, etc?

Night 2 of the beer traps yielded 2 slugs. More like one and a half, the second was really small... Should I be drawing any conclusions or too soon to tell?

hahaha...

So I was just providing FREE BEER when I used a shallow lid for 3 nights and never killed any. I've got to try again. At least I used a beer I would never drink for this sort of thing, so no loss to me :)

Are there any problems accociated with leaving the beer traps in place? Like attracting flies, fruit flies, ants, wasps, mosquitos, etc.? I know some of them are beneficial, but some aren't...

You can leave the beer traps in place all season, you'll just have to refresh the beer occasionally. I honestly don't know if it will attract any bugs, or wasps. Never gave that a thought, as slugs are the nasties, LOL

Japanese Beetles almost totally defoliated my basil overnight.
DOES ANYONE KNOW WHERE I CAN FIND INEXPENSIVE NETTING.Anything that will kill Japanese Beetles is not good to put on anything. HELP I'm loosing all my Basil..
Richard