The idea is to use one material, then use the alternate material if a 3rd treatment is needed. Tank mixing won't necessarily avoid resistance.

See link below ---

Here is a link that might be useful: how to avoid developing resistance with fungicides

Michael:

I use Captan 50 WP for scab control with great success.
However, you also mention Cedar apple rust. Captan will
not work on cedar apple rust.

Immunox (myclobutanil) is supposed to prevent rust if
applied in spring before full bloom. Immunox also
works to prevent scab.

I know others on this site have mentioned Immunox (myclobutanil) before. Harvestman uses myclobutanil with
great results.

I have not used it since I do not have CAR issues. Here in Wisconsin we have 3 cases of commercial orchards reporting scab after using myclobutanil. Our university suggests that we now have strains of the fungus that causes scab (Venturia inequalis) that are resistant to myclobutanil. I see Cornell posted a report about this also
for New York growers.

I do not know the situation on scab in your area if you have
strains resistant to myclobutanil or not. In my area, I see
it being used for CAR prevention or advised to be mixed with Captan and applied.

I have access to myclobutanil but have stayed with Captan
since CAR is not an issue.

Since many have success with myclobutanil, please do
chime in if you are in the Kansas area. I can only comment on what I find here in WI. Perhaps what I stated
is the reason why you want to use both fungicides together.

Actually, tank mixing is a standard way to delay resistance also and it is one of the reasons it's recommended by Cornell to mix Captan with myclobutanil for scab. The other is that myclo stays put and Captan will splash on new growth between sprays giving some added protection.

All you need to control scab in your zone is probably a petal fall spray and another 10-14 days later with Cap and Myc. If you are doing a delayed dormant oil spray anywhere from half inch green to tight cluster your can throw some myc (no cap please!) with the oil.

This is unless you are growing on a commercial scale with scab susceptible varieties- on that subject I'm no expert. However I've been spraying with this formula on scores of orchards (some of them a few acres) for 25 years and have never lost a crop to scab and rarely have even had any problem at all. Some sites I don't use the Captan- at least on the petal fall spray- especially if weather has been wet and cool. Captan can burn.

If it takes 10 years for a fungicide to develop resistant fungus on a 100 acres of Macintosh, I figure it may take at least 100 years, on average, to develop the resistance on 10 acres.

It seems to me that once a single fungus has resistance it quickly would spread throughout the entire orchard. I can't see how the math would work differently with this in mind- but I'm no plant pathologist.

Of course, I've no idea about the odds of resistant fungus moving distances from commercial production areas and whether the resistant fungus is at a disadvantage in surviving when competing with non-resistant on unsprayed trees. This would determine how well it could travel, I expect. Cornell only talks about development of resistance within an orchard.

Yes, I do have CAR galls erupting up the wazoo every year and am aware Captan does nothing for it but does work for scab. the mix is both to avoid resistance and to cover myself for CAR since they are both an issue at the same time.

To your point H-man, I may try the schedule you suggest for Scab, don't mind cutting back on unneeded apps. one bit if possible. I am curious why the Land grants I've checked and the 2014 Midwest Tree Fruit Spray Guide has such a lengthy schedule with so many apps.. If I understood the causal organism and disease cycle better it 's possible no doubt to reduce the apps.. Also, thanks for the heads up reminder about spraying Captan under slow drying conditions, forgot about that so it's going into my notes. Definitely keeping the oil weeks away from the Captan. I'd love to do a Delayed Dormant but, the way this Spring has been going it isn't looking very promising. The trees are almost all heirlooms and I have no idea about their resistance to scab.

Immunox has done anexcellent job on the CAR, I am fortunate to be able to monitor many trees a few blocks from the house and apple trees to know definitively when an outbreak occurs; in addition, I've learned to watch the weather forecasts and figure out if there is going to be an outbreak and get the Immunox on ahead of time on a few occasions.

Lately, I've been searching for another systemic and protectant that don't come in homeowner and quantities, no luck yet. some Penncozeb 4L would be nice, oh wait, Bonide already sells that and just calls it Mancozeb. Too bad the Bonide label id for ornamentals only, same A.I. in the same concentration and formulation as Penncozeb which is labeled for apples and is quite effective no doubt.

It really isn't as much about when the the spores are there as it is about when the trees are susceptible. I don't pay attention to what's happening on the cedars but the two insecticide sprays I do proactively occur just as apples are most susceptible so I only absolutely need to spray myclo then.

I'm in a region of extreme scab pressure and I assure you Cornell suggests just as many sprays are necessary as what your are reading there.

I always say that you can't know what pesticides you need if you are over protective of your trees. Even if you start to see some scab you can rescue the fruit with a spray after the fact. Not needing absolutely pristine fruit changes the game.

Addendum to my last post, I'm looking for protectant and systemic alternatives to Immunox and Captan in homeowner packaging sizes that are labeled for apple for CAR and Scab. Fat chance I suppose.

H-man, agreed and again thanks for the reminder about when the trees are susceptible being critical for sprays. I read recently about new leaf size or was it age, being a susceptibility indicator on apple; of course, I forgot to put it in my notes. No doubt CAR and scab wouldn't nail trees at green tip.

Mancozeb is not very expensive and is the fungicide of choice by Cornell's thinking to work with myclo or without it. Takes care of CAR as well as scab. I don't know if they make it in a smaller package but I believe it lasts a very long time in dry, cool storage.