*Safari is no more effective than imidacloprid, but a LOT more expensive. Since imdacloprid moves into the tree slower, you need to have it down earlier in the year (I apply in March/April). Safari is a good option for summer treatments so it gets into the tree right away. The other place for Safari bark sprays if if you want to treat trees in an area with high water table where it would be inappropriate to soil inject.
*The studies I have seen (OSU and MSU) all say that pentra bark does not improve the effetivness of Safari. It certainly has its place, but I don't think this is one of those
*IF you are going to use Safari, you only need to reach the 5-6' high...there is no need to spray the whole tree (and I don't think that is permitted on the label - is it?). One gallon of mix covers at least 65" of trunk diameter, and you want a low pressure spray, so I'd to the backpack sprayer. 5 gallons will treat fifteen 20" dbh trees. That is not that much pumping. They also make engine powered backpack sprayers.
*If I had the job, I'd soil inject imidacloprid. I use
this soil injector with flow meter and can run through those pretty quickly. If they want more, you can also soil inject Safari (might be able to tank mix the two???...I haven't checked up on that). Tree-AGE is really the better treatment, but that many trees could take quite a long time. It is really no more expensive than Safari even accounting for the time it takes to apply. Tree-AGE is good for 2 years, while Safari requires annual treatments. So your Tree-AGE will cost more this year, but a 2 year average it will be close to Safari..actually less based on my fee schedule.
