1) When you are mixing chemicals, it is best to do a test mix first, I usually use a 1 gallon jug with water and mix in the chemicals in question and shake it up and see if there is any reaction such as clumping or anything that looks odd. It's going to be trial and error as each company can't feasibly think of every possible combination to say it's safe to mix.
2) I usually just spray any extra that I have on my neighbors lawns to create a buffer zone between there weed patch and my lawn. Not sure what to do if that isn't an option.
3) Yes, I have mixed a half dose of Certainty in 1 Gallon of water to spot spray, it just won't go as far if you are broadcast spraying.
4) It all depends on the level of infestation you have, if it's going to take more than 1-2 gallons of product to spot spray than I would definitely think of broadcast spraying.
2) I usually just spray any extra that I have on my neighbors lawns to create a buffer zone between there weed patch and my lawn. Not sure what to do if that isn't an option.
3) Yes, I have mixed a half dose of Certainty in 1 Gallon of water to spot spray, it just won't go as far if you are broadcast spraying.
4) It all depends on the level of infestation you have, if it's going to take more than 1-2 gallons of product to spot spray than I would definitely think of broadcast spraying.