Originally Posted by RigglePLC
Green made a good point. What nozzle do you plan to use? Myself, I would never do a spot spray with a flat fan nozzle. You would tend to get straight line burns, where you stop and start. If you waved the nozzle, you would get zig-zag burns. A solid cone nozzle might work. Spot spraying is a good bet with a backpack. Chemlawn gun is a better bet with spot spray. If you have a skid sprayer--why would you spot spray since it is less effective, and almost as much work as spraying overall?
Use about 1 gallon per thousand sq ft. 2 gallons also works fine. Be sure to calibrate carefully with water and time yourself with your usual walking speed, so you know how much area you cover per minute. 1500 sqft is typical.
I do spot sprays with a fan tip. However the application rate always equivalent to the broadcast rate for a whole lawn. For example, if I am applying 2 gallons per M with a multiple nozzle boom, I use the same size nozzle and the exact operating pressure at the end of a single nozzle wand. I make one pass over the weedy area. There are no burns or marks in the grass unless it is MSMA, but If I almost never spot MSMA, that is what a paint brush with glyphosate is for. To be honest, I do not spot spray lawns very often. One very knowledgeable sod grower told me that there are weeds that have not broken above the turf canopy yet. You do not see them if you are walking around only spraying the big weeds that are visble. But if you broadcast the whole lawn, even the weeds that are not immediately visible will be killed. Makes sense to me. If it is broadleaves that I am dealing with, I come out looking like a star by adding Gallery to the tank and ending the broadleaf weed parade for a year. With the label and local restrictions on the use of broadleaf herbicides, I rather not have to spot spray all the time. In my climate, that is what happens if you do not broadcast treat a lawn and add Gallery or simazine.