Could be BDM, but looks more to me like it is unhappy with the pot. AFAIK, BDM does not cause leaf edge necrosis like that, and I can't see that well but I don't see the telltale dots.

The "tell-tale dots" are all over the underside of the leaf. I hope it is NOT basil downy mildew but the local plant pathologist thought it worthwhile to check. He didn't know what it was just by looking either.

Other pictures showing similar leaf necrosis with basil downy mildew may be found at:

BDM at NCU

See figures 2 and 3 showing typical browning of leaves.

BDM showing necrosis of leaves

NCSU extension agency report on 2014 outbreak

Basil downy mildew can be overlooked by growers because the initial symptoms tend to be subtle: the plants exhibit slightly yellowing leaves as their most noticeable symptom, which may resemble a nutritional deficiency. The dark fuzzy-looking sporulation occurs on the undersides of the leaves.

Lots of pics showing leaf necrosis there.

I hope to high heaven it is not BDM. I did not see any yellowing of the leaves before this happened which seems to be typical. It did occur rather quickly, in about 3 days from looking fine at a glance to obviously being NOT fine, LOL! Probably about a week from looking like the less affected plants which only show signs of damage on close inspection to being obviously damaged.

As for it being "unhappy in the pot", they're just seedlings not yet ready to transplant up. Soon, but not yet. It seems odd that the Thai basil would be OK with the deep root paks but the regular basil would not. The plants were well-rooted, but not root-bound. I don't think the issue, whatever it was, was with the flat they were seeded into. Its never been a problem before, and I've had those flats for almost 10 years (and yes, they were properly cleaned and sterilized before each use).

But who knows. The plant pathologist will know soon enough. I hope to hear from him in a couple days.

Hopefully it was something I did that messed them up - because that can be fixed, but BDM cannot.

This post was edited by zensojourner on Fri, Oct 17, 14 at 12:21

I would just sow new seeds... the plants are small and don't seem worth the worry.

BDM is widespread.

If my plants had basil downy mildew, it would just about have to be because the seeds were infected. These were grown indoors. If I plant again from infected seed, it's just more of a waste of time and increased risk to my remaining Thai basil plant. If this is BDM it will be the first case of BDM in this state. So, its not widespread here - yet - and hopefully won't be.

Say it is BDM - and it did come from infected seed. Then resowing the infected seed increases the risk of BDM becoming established in a state where it has up to now not occurred - or at least it has not previously been reported.

I'd rather wait until I hear back from the plant pathologist. Hopefully it is NOT BDM, but is instead something I can fix.

Well the report is in,and it says NO PATHOGENS NO PESTS.

"Healthy appearing plants. No pathogen nor pest found from sample."

So it is NOT BDM, which is a relief and an embarrassment at the same time.

They sure didn't look healthy to me. I have NO idea what caused the sudden appearance of necrosis on the leaves of the sweet basil. I've never seen anything like that before. For me, basil has always been a drop it and forget it kind of seed. But apparently I MUST have done SOMETHING to cause that, I just have no idea what.

This post was edited by zensojourner on Sat, Oct 18, 14 at 0:01

Again, they look unhappy in the pots to me. They are large and should be outdoors in good soil. I wouldn't bother transplanting the sick ones though just sow new seeds. You must be in a very warm climate to be planting basil this time of year....

This post was edited by Peter1142 on Sat, Oct 18, 14 at 10:02

I think you are falling prey to a perceptual error where a close-up picture of a small object seems to be much larger than it actually is. Those are large photos taken very close to the plants.

Typical advice for transplanting basil out of seedling flats is to do it when the basil has 2 sets of true leaves and is 3" tall. But that is for standard flats; a standard 1020 tray is less than 2.5" deep.

My deep cell pak is 4.5" deep. With the deep cell pak I often do not need to transplant out at all, when starting seed for planting outdoors. Most plants can go straight from the deep cell pak to the garden, if I've timed it right. That's why I like them.

The tallest plant was the leggy one at around 3.25"; the rest were only 2" or so tall. The tallest (leggy) plants were just getting around to putting out their 3rd set of true leaves, and the shorter, stockier 2" plants only had 2 sets of true leaves. They are not yet too big for the deep cells in the pak. They're not even really too big for the shallower flats had I been using those.

I've also never seen a plant that was in too small a flat end up with leaf necrosis like that, or cause little black or brown dots all over the leaf.

But maybe I'm wrong, and they are "unhappy" for some other reason in their deep cells. Other than the cells being too small - which is not the case - what kind of "unhappiness" is it that you suspect to be causing a problem, and what is the problem you suspect?

I'm wondering if they were too close to the fluorescents. The ones that were worst were the leggy ones that germinated just when we got 3 days in a row of cloudy weather (before I had them under the lights they were in a sunny south facing bank of windows). So they were taller and closer to the fluorescents - so maybe the crispy edges were caused by being too close to the fluorescents.

I've never had that happen before, AND I had a fan running on the same timer as the lights - but I guess there's a first time for everything. And I think I have been running the ragged edge of acceptable distance because I've been trying to keep the lights as close as possible for the shorter plants in the other cells. I must have pushed it too far.

I am going to try cutting one of those flats apart into 8 2x2 paks and see how they hold up. I just don't start 32 of the same sort of plant anymore all at the same time. Hopefully that will allow me to move plants around and keep similar heights together on different shelves so I'll be less reluctant to move the lights up for the taller plants.

The more I think of it, the more I think I must have accidentally fried them, fan or no fan. I just can't think of anything else that would have caused that, given there are no pests or disease present, and would still have left the healthy root systems they had.

It sounds like you have plenty of experience growing basil in flats so I don't really have any further advice. Are you using the same soil you always do?

I have found basil to be very hardy for transplanting.

This was a great thread - thanks for sharing.

So where did you find a plant pathologist, and what was involved in getting him/her to help?

@Peter - No, I was using a bag of Miracle Gro Moisture control which I accidentally bought last year thinking it was a bag of MG garden soil.

I have never used a bagged potting mix before, I usually mix my own and have for over 40 years. Still, everything else that was started in it over the past year has been fine. I even have a Jasminum sambac that I almost lost over the summer, repotted into the MG, which has since bloomed copiously and started putting out new leaves.

I doubt its a great medium for long term use, but its been OK for seed starting other things, including my murraya koenigii, and in the short term for my jasmine.

Years ago my preferred mix was 1;1 good peat and coarse vermiculite but I've not been able to lay hands on the coarse vermiculite for something like 15 years. Last time I special ordered - I ended up with a giant bag of medium grade, and then the nursery tried to convince me that was as coarse as it has EVER come. Sheesh!

So I've been working with less than acceptable potting mixes. I have most often been using 1:1 or 2:1 peat-MG garden soil which, while not AT ALL optimal, at least let me start plants for putting out in the garden. It worked OK for container grown veggies too. It would have been horrible for houseplants - so I just haven't had any house plants for years until I picked up that Jasmine a bit over a year ago.

Basically I haven't been happy with my choices for potting mix for years and this past year I've gotten REAL serious about finding a better solution. I'm still working on it. My son thinks I'm nuts, LOL!

I have never had disease in my plants, other than cucumber beetles and squash vine borers spreading bacterial wilt and powdery mildew, I think it is, respectively - since they scared the few companies making rotenone into stopping manufacture of it for sale to backyard gardeners - you can still buy it by the gallon for fish kills, which has to be the WORST possible use for it - I have never found anything effective at protecting my squash so I've just stopped growing it at all. Row covers are too hard for me to deal with.

Anyway I can recognize a lot of plant diseases but I've never actually HAD any in my own plants (other than the ones mentioned above). I had never seen anything like this on a plant, let alone a seedling still under lights, couldn't find anything that looked remotely like it - except maybe basil downy mildew, and scared myself into thinking that must be what it is since it looked so unfamiliar. Even the pathologist wasn't sure.

The one lonely remaining Thai basil is fine - so were the other 2 he took for testing. But all my sweet basil was turning crunchy. I just can't think of anything other than accidental frying from being too close to the fluorescents that would have caused it. The Thai basil were all shorter than the sweet basil, and the taller the sweet basil was, the more obvious the leaf damage was.

I would think some kind of disease - in fact I DID think it was some kind of disease - but the plant pathologist said definitely not - so it HAD to be some kind of mechanical damage. No fertilizing has been involved so it can't be chemical burn.

I just can't think of anything else. Maybe sweet basil is just way more susceptible to leaf damage from even the fairly low levels of heat from a couple of fluorescents or something. I'd never seen anything like it - but I've also never been so fanatically obsessed with keeping the lights low (for the 20 curry leaf plants in the rest of the pak that came up at varying times so they are varying heights).

Being that close to the lights hasn't fazed the m. koenigii at all - in fact they are growing great, if I can manage to stop underwatering them every once in awhile - but maybe the basil is just more tender.

I'll try again with the basil, once I've got the curry leaf plants out of the flat and into individual pots on a different shelf.

I'm just REALLY embarrassed that I scared myself into thinking my basil had a horrible disease and escalated it so far, only to find out there was nothing (pest or disease-wise) there.

@gossamer - your state agricultural department will have plant pathologists on staff. Often they charge for this sort of thing - depends on the state, but funding is generally pretty minimal these days so they can't do as many things for free as they used to. In this case, they are watching the spread of basil downy mildew very closely. The plants were obviously damaged in some way, it didn't look like any typical basil diseases, and it was suspicious enough that they took the plants and did the testing.

Check with your local extension agency first if you have questions about a plant disease and they can usually guide you to a state Ag department plant pathologist if it seems warranted.

Thanks so much for your help. That's good to know the agricultural resource is there if I need it.

As for planting soil, I really wish I had the time (or enough knowledge) to make my own mix. I believe my father-in-law ordered vermiculite online and probably has some left.

I have an unopened bag of MG Moisture Control which the nursery recommended for indoor plants. Is that not suitable for indoor herbs? Is there really a compelling reason to not use it? I'd rather not have to re-purchase something I already have if I can make this work.

I did have fungus gnats last year, and I suspected they came from the soil, but I also had purchased a few of the plants from the supermarket (now I know that was a big mistake), so I'm now thinking that's where the gnats came from...

I'm thinking that if I use the MG Moisture Control with an inch or so layer of sand on top and a small fan running inside my florescent grow tent should be good enough to keep away the gnats.

I'm not a MG hater like some on these forums, and it will be ok for a year or maybe even 2 for a houseplant. I've never had fungus gnats from it. I haven't used it (on purpose) for literally decades but I have used it in the past. I think the only time I've seen fungus gnats was back when I still thought using compost in containers was a good idea (it isn't, LOL!)

I don't think that sand will help with fungus gnats but I'm really not sure. There was a thread recently where I posted about how to clean up after an infestation - I think she ended up using cinnamon to discourage fungal growth, which in turn will leave fungus gnat larva with little to eat. I cannot for the life of me remember what forum that was in. I lose threads here all the time, LOL!

Fungus gnats are usually an indication that you're over watering. Since any peat mix is highly water retentive, watering a peat mix requires more attention to detail at times than some other mixes. Since I have a tendency to UNDER water, peat mixes work really really well for me because they hardly ever dry out too much before I water again.

So basically, no, I don't think there is a compelling reason not to use it. I've been using the bag I accidentally bought and everything has been fine. You might open up the grow tent once in awhile and let the fan sort of flush it out.

I don't know what your situation is - but I have rarely found humidity to be an issue with the garden variety types of plants I grow indoors. I'm in high desert now and growing tropicals under lights with no tent or other humidity-preserving mechanisms, have an oscillating fan running whenever the lights are on, and the little tropicals are fine.

I'm sure there are plants for which humidity is a killer issue, I've just never grown any. Rosemary, maybe. I've never done well with indoor rosemary - but then I've only ever tried to keep those forced ones they sell around Xmas, which probably weren't going to survive no matter what I did, LOL!

Making your own mix is easy, if you can locate the components you need. There's a ton of information about that on the containers forum. Some of it is a bit contentious sometimes, but lots of information over there.

Basically a 5:1:1 mix is King over there - that is 5 parts pine fines (Personally I prefer a higher proportion of peat. I'm not a peat hater and I'm used to working with it, YMMV. But having only recently found possibly acceptable pine fines I don't have a tried and true proportion yet - I'll start with 3:2:1 bark - peat - pumice blend for container plants. Because I hate perlite with a (possibly unreasoning) passion and where I am now I can get pumice easily.

That said - if you don't want to mix your own - I'd ask around for better options than the Miracle Gro. I've been using it because I had it on hand (having bought it by accident), and I have no qualms about using it for single season containers or seed starting, but for the long term, you need something that won't break down so quickly. Something with more bark and less peat and "forest products". I like peat - but MG is well over 50% peat and that's a bit much, IMO, for long term use.