Brandt TriTek is not labeled specifically to kill caterpillars, but since caterpillars are a soft-bodied insect, this product could kill them whether they're sprayed directly with the product or if the caterpillars make contact with leaves sprayed with TriTek.
According to the manufacturer, the longest you could leave Brandt TriTek (OMRI) mixed in solution is no more than 48 hours.
The Brandt TriTek product label recommends for ground applications to be applied as a medium or coarser spray (ASABE standard 572), and the minimum volume mean diameter (VMD) for spinner atomizer nozzles using a nozzle height of no more than 4 feet above the ground or crop canopy. You may contact Brandt directly for more specific information at 217-547-5800.
The Brandt TriTek (OMRI) label does not indicate or make any recommendations that it is necessary to check the ph levels of the water in your tank.
The number of times you can appliy Brandt TriTek depends on the crop and pest that is being treated. Please see the label for specific application times.