So, 8 years ago, I bought some "Messenger" and used it on my tomatoes and got a bumper crop and I mean WOW! I wasn't able to garden tomatoes since then, until this last year, and had 2 more packets left. So I used another packet and WOW! I have another bumper crop, even though we had a slow start of a summer, and all my neighbor's have very few on their small plants... So I know this stuff works! I just looked it up, and Messenger had been bought out, and you can now get the product this way (have to share) http://www.gardeningthings.com/organic-natural-fertilizers-biostimulants-c-67/employ-reg-plant-health-promoter-2oz-package-p-183. The only other things I do, is use wall of waters and get my plants in earlier than normal, apply a one time small amount of Lily Miller fertilizer, and also spray with Neem (have only had to do it once this year).
I just wanted to share this information with you, because it's worthy of sharing. It's not bragging, it's sharing, because I want all of you to have great results as well! Oh yeah! Full sun, and clip and dispose of dead leaves... common sense, right?
Carolyn, who notes that there have been many newer products since Messenger was released that I see folks at other message sites using. Don't ask b'c I can't remember them all but one I know is called Excel and another one azo something or other. LOL. I don't use any of those products on my tomatoes just b'c I don't think I need to.
If you click the link that I offered above, Messenger's name was changed to "Employ" when it was sold, and now rather than coming in little packets, it comes in one container that you use 1/4 a tsp per gallon, so it is actually cheaper now, than when it was Messenger. I truly like it and have used it on my tomatoes and my peppers twice now, over the years, and when I use it, I get a bumper crop. I spray in the morning and when it is shady. I also use Neem on all of my garden plants, and get good results against insects and fungus with that - which reminds me, I should probably do that in the morning, as it's been awhile.
Karrie, I did read your link and I said above that harpin was being sold with different names at different sites, and not as Employ which is what it's being sold as at the link you provided, and here's one example, note the date is 2012 since many of the Messenger links via Google are from years ago.