Are you mean to tell Stamper to use Immunox, fungicide spray (or in your case, a brand called Rally) to fight apple scab?

I am old school and still use captan & Imidan in my 20 tree
hobby orchard. Perhaps because it is readily available for me and that is what I used many years ago at a commercial orchard I worked at in the 1980's.

I spray Captan at green tip to petal fall every 7 days
for primary scab control on apples. At petal fall thru mid-June I spray
Captan 50 and Imidan 70 every 7 days.

After June 15th our curculio season is usually over and so
is the period for primary scab infection. At this time I go to
my summer spray schedule and spray captan/imidan every
12-14 days thru mid-late August but stopping at the correct
PHI for every fruit crop that ripens before late August.

I will stop spraying peaches by July 25th and early pears
by August 1st in my area. I prefer to err on safety side and
stop well before the PHI listed for each crop. We do have
maggot issues on apples in August so I like to make sure my apples are covered at least thru August 20th for good
control.

Again this is old school using a calendar method for spraying but it works for me and for what I grow in S.E. WI.
Your pest issues may differ from mine pending what part of
the country you are growing fruit in. Control will depend on
what you choose to spray with, availability of chemicals, and how much spraying you are comfortable with.

Some on this site do well with few sprays and are great at monitoring for insect populations to apply controls at the critical time.

I forgot to state that if you do use Captan/Imidan as
you mentioned, the rate is 2 tablespoons/gallon for Captan 50 and 1 tablespoon/gallon with Imidan 70.

I trust you will be using the proper safety equipment if spraying these chemicals. I don't want to advocate spraying without safety in mind for any chemical.

I'm in southern NY and 2 applications of Imidan is all we usually need for apples, although apple fly maggot is a problem at some sites in my general region which might require another two. In the 100 orchards I manage they've never appeared and the only times I've needed additional insecticide is at a couple sites for stink bugs and Jap beetles.

Why would you spray Captan every week to control scab when a total of 3 or even 2 myclobutanil sprays works just fine in the usual pressure found in a home orchard? You can throw some Cap in the mix if you want to make sure growing tissue gets a dose after rain (captan splashes), but I've not found that necessary.

Imidan is a very useful insecticide and does a good job on most of the insect pests of fruit trees but it is a pain to mix in small batches. Be sure to have a dust mask, at least, along with everything required by the label, if you are going to cut open the water soluble bags.

I've never used copper, although I bought some an intend to spray my apricots with it to help with bacterial spot, but I've never had the need for it on any other fruit trees I manage. It is supposed to help with fire blight but even if I don't treat FB it usually doesn't return the year after it makes an appearance for me.

Unnecessary sprays can lead to outbreaks of mites and scale as you eliminate beneficial predators. Although Imidan is relatively kind to some of these it is still best to use it only when you are targeting a known pest.

I've had very good results with the commercial formulation pyrethroid I use (Asana) and haven't suffered from its inability to kill the eggs already laid in the fruit even though I wait for last apples to lose petals before doing the first spray- even on plum trees that dropped petals as much as 2 weeks before. This is at scores of orchards for the last couple of years.

You may still be able to obtain Imidan on-line or at sources in CT such as Valley Green if you call ahead.