The library gives a range for wetting agent in foliar sprays, not a single ratio.
Drake says to use 2.5 to 12.5 liters of soap per 100 gallons of water. (Office Hours Ep. 24, 25:37) Test it on a plant first. (Office Hours Ep. 24, 25:37) Add more if vinegar cleanser is in the mix. (Office Hours Ep. 24, 25:37)
The 1:100 figure shows up in a different spray. The canker, black spot, pear rust and brown blotch recipe uses 5 liters of Jadam wetting agent and 1.5 liters of Jadam sulfur in 500 liters of water. (Office Hours Ep. 121, 49:43) That is 1:100 for the wetting agent, but it is a disease recipe, not a maintenance spray. (Office Hours Ep. 121, 49:43)
These sources do not say whether 1:100 is still the maintenance rate. That needs Drake's answer on the show.
Sources
