I have decided to spray insecticide this year on my tart and sweet cherries in order to control cherry flies. Unfortunately, the PHI is 14 days. Is there a good way to determine when I should stop spraying?
Days from petal fall?
Color change in the cherries?
Another related question would one spray at petal fall be enough to give decent protection? I am spraying Spectracide Triazicide.
Spinosad would be a better choices.
Thank you for your reply. I see spinosad has a PHI of 7 days so that would certainly help.
I dug thru my old notes and was able to answer my own question. I thought I would post what I found in case someone else has the same dilemma. For me in central Illinois on the 5/6 hardiness zone border for 2017:
Montmorency on Gisela 5
4/13 70% bloom
4/15 95% bloom
4/19 petal fall
6/6 start of cherry harvest
6/12 final harvest
So from petal fall to harvest is about 47 days. I am sure this varies some from year to year and may not apply to other tart cherries. But it does give an idea of how many sprays you can make.
I also found a maturity chart for cherries and other stone fruits on Grandpa’s orchard which should be helpful.