All these except the $348 one assume you will be injecting fertilizer into a hose and then irrigating with it. I don’t know for sure if they would work near the hose end with low flow rates. “3 GPM” sounds like a lot more than a hand sprayer puts out.
Also, they mix at least 19 or 99 parts water to one part concentrate. Would your bug spray need to be much less concentrated?
http://www.mortonproducts.com/... (lists 3 options)
E-Z Flow - E-Z Adjustment, (100-1 to 2000-1) http://www.mortonproducts.com/... $57
Adjustable Dosmatic Fertilizer Injectors
http://www.mortonproducts.com/... $348 - $675!
Here’s a good review article that makes the E-Z Flow option above sound good.
http://www.noble.org/ag/hortic...
Most commercial injectors ...
“... are designed to be coupled with watering wands and sprinklers having
flow rates of 3 gallons per minute (gpm) or higher”
“consider using a Grow Pro brand injector which costs around $30. Unlike the siphon mixer, the Grow Pro has a built-in 12-ounce reservoir”
“EZ FLO injectors .. . The 3/4-gal model is priced around $70”
The article also mentions a clunky DIY injector “assembled from a new or used pump-up hand sprayer and a few pipe fittings for under $50”
