Maybe sunlight is too much for the young plant. With only 2 sets of leaves its not a good idea to expose to bright sunlight for a few more weeks. even for that, just a coupe of hours per day. Careful watering, dont get water on the leaves. An insect may be causing this problem, like a spider mite, but its too early to know yet. What is the size of the pot, and what was the growing medium used in the pots. When my tomato plants are put out in my greenhouse to harden off, they are usually 2 feet tall or more. The leaves turn tan color if they get too much sun (bleached). I coat the outside of the greenhouse with some whitewash which helps to reduce strong sun. When it rains the whitewash turns clear to let more light in. Suggest that you take them indoors and, only give them an hour or two of sunlight per day, until they get about 4-5 sets of leaves. Do keep them in a sunny window however.

Italian, I was growing some beautiful Lime and Lettuce Leaf Basil in a pot under lights, then started putting them outside for a few hours each day. Mine had the same problem with transparent leaves, then the leaves started turning brown and falling off! I haven't fertilized them. I've been trying to figure out what happened. I know something called Fusarium Wilt (sp) attacks basil, but I'm not sure if that's what I had. The same browning of leaves happened last summer to me.

I too have the same problem with a Magical Michael basil. It is in a cooler area of the house, but it's growing next to Genoese Basil which is doing very well.

The leaves were being burnt for several days from evening Western exposure, so I started closing the blinds. I don't know if this direct sunlight was the cause.

Here is a link that might be useful: {{gwi:887379}}

Can you move the basil outdoors? It would do much better outside with plenty of sun, as basil LOVES sunlight. The spots look like water or fertilizer splashes that got onto leaves. Just a few hours of sunlight per week will give you very puny plants indoors, and are more prone to diseases and other damages. It could even be from fungus gnats, those tiny flies that infest all the houseplants it can find indoors. Its maggots will eat roots and slowly kill the plants that way too.

Thanks. I've started hardening them off now. It got a nice sun bath for a few hours today.

I'm afraid of getting whiteflies or aphids from the outdoors, which is why I've been reluctant to put them out.

All this time, I had been supplementing with indoor lighting for 2-4 hours after sunset. (I'm in Zone 6, so I have been waiting for warm weather to put the plants out.)

You say that basil does not like water on it's leaves?
Certainly the Genovese basil's leaves kind of hang down, which makes it seem that they like the water to just roll off.

Water while in bright sun, can cause scalding. My basil was plated outside about 3 weeks ago. I used to see white flies only on string beans, and these were pole type beans. When I grow under plant lights, the plants see 18 hours of it per day. Aphids son't usually bother basil. Neem sprays are the best to use for any herbs that might get bugs. I also used yellow sticky traps for catching some bugs like fungus gnats and cucumber beetles.

mezzoforte - you are more likely to suffer from pests on your plants indoors than out. Aphids like the calm conditions indoors where they don't get disturbed by wind or rain and have no predators. Outdoor plants are tougher and more robust because they get plenty of light and do not become weak and etiolated. Also they grow more robustly as they have to contend with air movement. Give your plants fresh air as soon as it is warm enough for them to go outside. As to watering, it is a good rule to always water at the base of plants. Not only does this avoid scorch and moulds it also conserves water. You are only put it where it is needed.

Lady bug larve love aphids!

Thanks again! ksrogers, you say that Neem oil is okay for herbs? But how does it wash off, and won't it leave a bad taste?

I have fungus gnat in my soil (from having the pots indoors!). I was told at a nursery that I should repot it and throw away the old soil. I'm going to do this, but I've read that putting sand/perlite on the surface will make it seem dry, so the adults don't lay eggs.

Do you think that yellow sticky traps will solve the problem, because I think of them as more of an indicator that there is a problem than a solution in itself. I had a whitefly infestation last winter (indoors), and had used sticky traps, but it didn't actually stop the infestation :(

flora, I think I understand what you mean about outdoors being better. Though indoors, I used an oscillating fan on the seedlings for a couple of hours in the evenings, to make them stronger (though I don't know if it had an effect or not).

I also do try to bottom water (though I was not for the basil because the pot is large!), but I water the top at the same time I bottom water, so the whole soil gets completely soaked. Is this bad in general? Should I just get the bottom half wet and leave the top drier? (That might discourage gnats from laying eggs.)

Anyway, I was told at the nursery that basil has tricky watering requirements, and I should water more frequently and lightly; they are very susceptible to root rotting she said. And I think she meant to water from the top. I was surprised, because houseplants you water less frequently and deeply (but she's something of an expert, so I trust her advice).

Cheers

Neem oil is a mild insecticide that is sprayed on herbs that are being damaged by chewing insects. Fungus gnats might die if sprayed directly with it, but the gnats job is to fly and lay eggs everywhere. There is a form of Bt mixed with water and drenched into the soil that can kill the maggots, Yellow sticky traps have to lay flat, horizontally for them to show any infestations. I had some this spring indoors and can only think that it may have come from some reused pots. In my garden, I apply a benefical nematode that is watered in and will go after the fungus maggots. Also another nematode type will go after grubs. Removing all infcted soil will not completely get rid of the maggots, as they feed on the roots. A few soil drenches with a Bt will not harm the plant but will stop the cycle of maggots and then the gnats.

I put the plants outside and they seem better now. I tried to let the surface be dry for periods of time and there is also some bark mulch on top (which gets quite dry). I also put the yellow sticky traps like you said and it caught a few initially.

Would just running soapy water through the soil work to kill the fungus gnat lavae?

Here is a link that might be useful: I found this answer

Soapy water might help, but because its not something roots normally see, it can also kill! Bt is a liquid mixed with water and that can easily kill the fungus maggots in the soil. Avoid the woodchips as that just helps the bugs and maggots to thrive better. Neem after its sprayed on herb leaves, will usually dissipate after a couple of days. Simply washing the leaves before suing will remove 99% of any leftover traces. It isn't normally absorbed into foliage. Below is a great example of how Bt works on these maggots and most caterpillers. There are a few different forms of Bt, so this one is 'cultured' just for the gnats and thei offspring.

Here is a link that might be useful: Gardens Alive

I've read in a couple of places to syringe basil leaves in hot weather. Does this make sense? Would misting work too?

I thought that it was better not to mist in bright sunlight because the water only magnifies the light on the leaves and scorches them.

I also thought basil doesn't like misting.

No misting! Basil is just fine in bright sun and heat. It does need watering, but you definately should avoid spraying or misting the leaves unless its badly wilted from lack of water and is only misted after the sun has passed over and its in shade. Syringe?? The only plant I know of that can benefit from the use of injections with a syringe is a squash plant, that has vine borers. There, you either use a weak Bt formula or beneficial nematodes.