For those of you who have used or are wanting to use SM-90, let me pass on something that has affected me. First of all, SM-90 appears to be a great product not only for bug control but also to help root colonization. SM-90 apparently has many benefits other than this but I chose to use it as a on-going regiment against insects.
I first spotted a problem a couple of weeks ago as my plants were developing yellow leaves at the lower branches. This was followed by necrosis of these leaves. I also had a few leaves exhibiting intervenial chlorosis (yellow of leaves with green veins). Of course my original thought was a nitrogen deficiency and possibly a phosphorus deficiency but I am using Advanced Nutrients entire 2+program, so nitrogen or phosphorous shortage seemed unlikely. I had been foliar spraying a mixture of SM-90 and water of the plants every three or four days and just misting them with PH'd water inbetween. I had been mixing my nutes at a PH of 6.3-6.4 so PH shouldn't have been a problem, or so I thought. Just out of curiousity I overwated my plants a couple of times and PH'd the run off and it tested out anywhere from 6.8-7.2! I then lowered the PH of my mix to 5.8 and feed a couple more times and then tested the run off and it was still hovering around 6.6-7.0! I couldn't figure it out! Why was the PH still so high when my nutes were PH'd so low?
Well, while pruning my plants last night and removing some of this yellowing plant material, I mixed up a new batch of the SM-90 foliar spray. I decided to PH this foliar spray and guess what? The spray with normal tap water (my tap water PH's at 8.4-8.5) was PH'ing at 9.4! I was told that because SM-90 is made up of with a lot of citric acid in it and that it would make it very acidic. This is NOT the case! I PH'd SM-90 straight from the bottle and it tested out at 9.5 or so! PH Down hardly even touches this shit. I had to put more PH Down in this standard spray bottle than I have to in my 5 gallon res for my nutes. It took at least a tablespoon to get this stuff down to 6.5! Here, all this time, I have been spraying my plants thoroughly with a 9.5 spray and wondering why my soils PH is so high when my nutes are so low. The plants drips into the soil after I spray it, so it has obviously affected my soil PH accordingly.
While SM-90 seems to be a very effective means of battling insects and help to colonize the root system, just be very, very careful to watch your soil's PH and pump that shit full of PH Down to get it under control! Now that I have done that the plants seems much, much happier and look very lush. Despite the intial problems here, I will be keeping SM-90 in my garden supplies now that I know what to look for in the way of PH. I just wanted to warn you guys and make you aware of what happened to me. Some of you may already know this. If so, sorry to waste your time. For those of you who don't already know? Be forwarned!!! SM-90's PH is high as hell and needs to be brought down for use with MJ.