Lettuce help needed

[Steve Robinson]

Can anyone advise me on this issue that's just come up in my DWC bed?  I've searched this forum as well as the internet and can't identify it.  Older leaves begin to wilt at the edges progressing until the entire leave turns white and dies.  New leaves seem to still be coming on and growing well.  System is 150 gallon FT with two 50 gallon grow beds alternately flooding for 15 minutes and draining 45 minutes.  GB's drain into a sump which pumps into two small (5 gallons each) DWC beds and drain back into the FT.  Each DWC bed has aeration.  System is in my garage which is currently about 68 degrees.  Don't see any obvious insects on the plant and it seems to be confined to the more tender varieties of lettuce.  Everything in the GB's look great and growing fast!  Today's readings are Ph 7.0, Ammonia .25 ppm, nitrites 0, nitrates 80+.  I also used a soil test kit and got a reading on the Phosphorus and potassium which showed medium to high on each.  Maxicrop was added a couple of months ago when the system was started. Only water and fish food have been added since.  Thanks for your help!

[Vlad Jovanovic]

Well, at 68 Degrees your pretty much at the high end of the generally accepted "optimum" temp for many lettuce varieties (60 to 70), so you do have quite a bit of headroom as far as that goes...This is not to say that lettuce wont grow in warmer or cooler temperatures...(I couldn't tell from the pics on your page what else you have planted).

Heck, they'll even survive sub freezing temps (repeated exposure to such temps will tend to seriously injure or kill them though). 50-60 shouldn't be a problem. I've had lettuce growing (albeit slowly) in an unheated hoop house well into the winter...Actually the heads were much nicer, tighter, more compact than the ones that ones that developed in significantly warmer conditions...  

If your water temps are warmer than your air temps that will usually cause high humidity. So, depending on what fish species you are dealing with, you could try to kind of match your air and water temps a bit. This may help with the humidity. But, your relative humidity is smack dab in the optimum range for lettuce! (65%-85%)

Now that you have the lights a decent distance away from your plants, and you have a bit of air circulating with the recent fan addition, (I hope you used a different electrical outlet btw :)  if I were you (and this is just my humble opinion) I would just let some fresh (and cold) air into the garage a few times a day, sit back and enjoy! 

[Jane]

That may not be high enough to worry about . I would check with some of the commercial growers or Sylvia

[Jane]

how do the roots look are they white or brown ?

[Steve Robinson]

Jane, here's a picture of the roots.  They are a tan color...maybe brown.  Vlad, in the DWC I have mostly lettuce and a few basil.  In the media beds, I have peppers, tomatoes, cabbage, squash, cucumber and eggplant.  Everything else is doing awesome.  The problem is with only the most tender of the lettuce.

[Vlad Jovanovic]

Those roots look pretty good Steve.

[Steve Robinson]

Thanks for the confirmation Vlad. They're certainly long. Today I did notice a few small flying insects...maybe a gnat of some sort, flying in and out go the lettuce. Guess I need to get some sticky traps.

[Vlad Jovanovic]

They certainly look healthy too. Not brown and gunked up at all.

Yep sticky traps or the old the old apple cider vinegar (or wine) in a glass trick. Just put plastic wrap over the glass (secure with a rubber band) and poke a couple of pin holes in the plastic wrap. The gnats get in but wont get out.

Be on the look out for spider mites...a MAJOR bummer for indoor growers...but luckily there are a host of organic spray remedies you can buy to take care of them. Most of which involve a mixture of essential plant oils (2 to 4%) and a surfactant, like dish washing soap (.3 to .5%), and water. I've been making lots of 'fancy' homemade soap lately, so I have an arsenal of essential oils to choose from here. There is an interesting section on the topic of aphid and spider mite control near the end of this study...There's no need to read the whole thing unless your REALLY into Lavender and Rosemary plants.

 http://www.certifiedorganic.bc.ca/programs/osdp/OSDP-FinalReport_I-...

Most all of the organic products for sale seem to work on the same principle, using some kind of oils to asphyxiate the mites. Making your own is just much much cheaper.

[Steve Robinson]

More great advise Vlad. Thanks! I've put out a cider vinegar trap but haven't seen any more insects. I've looked carefully over several of the wilted plants and see no sign of mites. But, these old eyes aren't as good as they were in the past! :)

[Vlad Jovanovic]

Yeah they're pretty tiny. I'm positive the wilting had nothing to do with mites, just wanted to give you a 'heads up' since they are so damn prevalent when growing indoors and heated. They seem like one of those thing that a person is bound to run into eventually. I lost one my hot pepper plants to 'em last week. Well, sort of on purpose as I was using the plant as a kind of 'control group', spraying it with plain water (no oils). It appears that water actually helps a bit but not nearly enough. I dont think the mites enjoy the humidity. The plant got pretty weak really quickly, and all of the leaves fell of all at once. All that was left were yellow and green spicy Feferones hanging there, looking kind of like Charlie Browns christmas tree...The other three Spanish hybrid peppers that were infested seemed to have cleared up rather well and are going strong. You can actually watch the spider mites fall off the leaves in a tiny spiraling death throe in like a minute after being sprayed with the oil mixture...

[Steve Robinson]

I will definitely have to mix up some of that in anticipation! Not sure what the problem was but I don't see any further damage. Maybe wishful thinking on my part. Lol! Crossing my fingers!

[Vlad Jovanovic]

I'm apt to think that it was a combination of lights WAY to close, coupled with no ventilation, and that some of the more fragile outer leaves (which aren't at the top of the roots water distribution list anyways) couldn't replace water as fast as they were losing it. It sure would be cool if that were the end of it.

BTW...if you do ever end up using that oil mixture, use it sparingly as a little goes a long way and you want as little as is possible to get into your water. (And try not to use any products containing Neem Tree oil, as that particular oil seems to be toxic to the fish). TCLynx listed some pretty wise general guidelines for using oil/soap products in aquaponics in another discussion, you may have seen it...

Anyways...  hopefully you will never have to worry about such things...

[Steve Robinson]

I think you're right Vlad.  The lettuce is putting on lots of new growth and I'm not seeing any further damage!  I'm encouraged and really appreciate everyone's help!