I didn’t post everything I asked about spreader stickers and I will summarize something I think is useful. The turpentine based stickers like Nu-film may be superior for endurance of non-systemic pesticides to rain and solar degradation to the latex based ones, like what I use- Tactic.
However, if you are using systemic pesticides such as myclobutanil, Indar, or Assail, the latex based ones are better to use because they allow more penetration of the leaves with systemics, and therefore increase the efficacy of these materials. Now I know why my ag adviser long ago recommended Tactic over other stickers. It also sets sooner, which is helpful if you get an unexpected downpour after an app.
After 15 years of using an Assail, Avaunt (or Asana), Captan, Indar or myclo, and Tactic tank mix I can assure you that I’ve never failed to bring any of my orchards into a productive season due to fungus or insect pests. I have never observed any phyto-toxicity either.
Plenty of times it has rained a great deal between apps and I’ve never re-applied anything beyond my two post petal fall spring sprays. Wash-off has never affected results negatively- perhaps because of the systemics always present in my mix and because I use Tactic instead of Nu-film. .
I’m still far enough north (just above NYC) to be able to get away with only two insecticide sprays quite consistently unless stinkbugs or OFM strike later in the season.
I have found that I can control OFM with very slight applications of something like Assail only hitting the growing tips of peach trees- they never make it to the fruit if I control them at the tips. A couple gallons of spray can treat just about an entire acre.