CAPTAN 80 WDG How much per Gal


I followed the dosage discussed here so hopefully there won’t be a fungus among us…

I read the label of the CAPTAN 80 WDG and I came across this statement:

“Apply 5 LBS. per acre in 20-400 gallons of water using ground and in 10-20 gallons of water by air”.

I can understand the difference between ground and air but a "20-400" differential within one mode of application has me puzzled. Isn’t that such a large spread to the point of being useless?.

@Appleseed70, by the way Iin the label it says that if “adding sulfur, use only 2.5LBS” so adding sulfur is ok with Captan and is efficacious.




FWIW…if I’m honest, I don’t get the undersides of all the leaves. I try to get most, but my spray wand nozzle didn’t turn, so if you wanted to do that effectively, you’d have to lay on the ground under the tree to do it. I kinda do this a bit and it’s how I get a lot of drift on my body.
The new sprayer I ordered but haven’t got yet has a nozzle that can be turned upward…that should make things a whole lot easier. I do take a lot of time, and I’m thinking my coverage is probably as good as an air blast sprayer. Nothing is going to achieve 100% coverage.
I was watching video demos on YT of electrostatic air blast sprayers and they were making comparisons to it and a conventional air blast.


The sprayers they use create a fog that allows for high concentration sprays. It creates a much thinner coating than what a handgun sprayer does so you can often go with much higher concentration mixes.

Olpea, that makes sense to me. What I’m still a bit confused about is the much smaller rates for Captan I found on the Captec label than what you or Appleseed have come up with as far as granular Captan. Same active ingredient involved.

When I was using granular I came up with lesser concentration as well- with 80 I would have used a bit over half a TBS per gallon.



I’ve never used Captec 4L, so I’m a bit unfamiliar w/ it. I looked the label up and scrolled down to peaches (which of course is my interest, but apples have the same label). The label shows a max rate of one quart/100 gal. of spray, but it also shows a maximum of 4 quarts/acre. I notice the general instructions of the label indicate minimum spray volumes/acre. They list aerial as 10 gal., concentrate as 50 gal., and dilute as 100 gal. Since they mention this is the minimum, I assume they are referring to really small crops for the minimum. A full dilute for something like blueberries is obviously going to be less gallonage/acre compared to full grown peach trees. Blueberries (like tomatoes) are low to the ground and would require less gallonage/acre for full dilute (i.e spray to the point of runoff) compared to a much taller and fuller canopied peach tree.

As I read the label, the 4 quarts/acre max would convert to somewhat more active ingredient (about 20% more) per acre compared to the dry formulation of Captan 80% (a.i.) I use. I arrived at this calculation based upon per acre rates, accounting for the different concentrations of the formulations, and the different weights (by volume) of the dry vs. liquid formulations. In taking all these factors in account, and assuming my calculations are correct, I can not account for the 20% a.i. variation between the liquid formulation and the dry.


Going over details further, it seems peaches require twice the concentration as apples. Maybe theyare not as prone to injury from Captan burn. There is the source of my confusion- I have never used captan for peaches. I protect them with more modern chemicals- cost of materials is passed on to the customer.


The maximum application rate for both apples and peaches using Captan 80 WDG is 5 lbs. per acre. That is also the max. rate for anything listed save for almonds which is 5.6 lbs. per acre.

What is the more “modern” chemical you use?


There is the highest legal rate and the highest recommended rate. With a caustic chemical I’m not sure the best tactic is to run with the highest rate the law allows. I usually use the highest legal rate with insecticides, but that is generally the highest recommended rate as well. As this label shows, recommendations vary with the issue addressed.

Cornell recommends rates lower than those suggested here. I don’t think this is a question that is answered with a single number, but I have never relied on Captan and am just basing this on the sources I happen to have read.

I may be a bit cautious about Captan because the first large orchard I ever managed was sprayed independently of me and it was dosed with a heavy coating of Captan about every 2 weeks throughout the season- every tree in the orchard.

I don’t know what his rates were but the estate was managed with intense fear of failure and independent contractors were fired at the whim of an estate manager from hell.

At any rate, there was no brown rot or scab, but apple trees were ridden with mites and many plums had shot holes in the leaves. Nothing looked real healthy. I always suspected the constant very visible coating of Captan was at least partially the problem, for whatever that’s worth.

So when I use Captan, I use it at rates where you don’t see it on the trees or fruit. For brown rot I rely on Indar and Pristine. For home growers I recommend Monterey Fungus Fighter.

These compounds have less impact on the ecology of the trees, if only because they don’t leave a white dust that mites thrive in. They also don’t wash off in the rain and have kick back, which makes them far more reliable for someone who can’t constantly be on call to reapply fungicide after every heavy rain.


ok great…so how does any of this translate to peaches requiring “twice the concentration of apples”? Am I missing something here?


Brown rot must simply require more Captan to be controlled than apple diseases.


Not according to the label . The label is the law, isn’t it?

What leads you to say it is a “caustic” compound?

When using Indar, you are spraying a contact fungicide with it right? Captan?


Yes, according to the label I provided, higher rates are recommended for brown rot on peaches than for apple diseases. Cornell recommends even lower concentrations for apples.

Caustic, because it can burn leaves and cause fruit russeting. It also can cause shothole on certain plums, I believe.

I only use Captan in combination with SI or strob fungicide for scab control.

This isn’t to say that there’s anything wrong with using Captan as a pillar of fungus control- many commercial growers do. I am only speaking of my personal preference here. For me the price of materials is not terribly consequential compared to the price of application. Not so for commercial producers.



In reading labels more attentively (helpful, I found!) I saw mention of a particular droplet size and caution that higher pressure would reduce the droplet size as if that was bad.

I had been thinking that a finer spray driven at higher velocity would be more penetrative. Now I am not sure.

I can adjust the pressure and droplet size but the relationship is inverse. I guess different trees with different canopies would need different settings but generally speaking finer vs. coarser sprays?



It depends on conditions which is best. Generally finer is better and commercial agricultural sprayers (I forget the name of the design) create extremely fine particles as do mist blowers. This spray is a virtual fog that passes through spaces and penetrates everything. But this means an increased level of drift and in any kind of wind, mist is a nightmare.

With my hand gun I use a finer setting when conditions are still and trees are not too tall. With a hand sprayer I’m adjusting with every tree going coarser as I go higher until it is a stream similar to a squirt gun.

Stihl and Solo make 2 stroke powered mist blowers. The garden writer, Lee Reich, once told me he loved his Stihl. You can do highly concentrated sprays with one so it functions like a much larger sprayer given potential coverage. But he also told me that season that he thought he’d blown off all the flowers of his fruit trees and that was why he didn’t have much harvest. Not a great endorsement for the machine- or the writer, for that matter.

I don’t know any fruit growers that use one of these machines and I’m still waiting for another critique, particularly from someone whose used one for several seasons- successfully.


Mike have you sprayed your Captan yet? I tried mine out tonight and was concerned how well the WDG would dissolve. The agitation from the garden hose for just a few seconds was all it took to have them totally dissolved and in suspension. Sprayed real nice too.
I’m already a big fan of this WDG form, clean, neat to work with, sprays so well. Good stuff…I like it.


I sprayed it last Saurday(5/16) and I found that it dissolved very nicely and stayed in suspension easily with the in tank agitator.

I just have to get an accurate digital scale so I can use metric. The danger of using dry oz. and fluid oz. intrchangeably is too great.



I have that problem too. This is in regards to Imidan70-W where the suggested use rate for apples is 12 to 16 oz. per 100 gal. If I mix 3 gal. at .16 oz. per gallon I need .48 oz. of Imidan. I’m assuming that’s dry weight since it’s in powder form and I have a postal scale that I can measure out .5 oz. of the stuff. Is that how I should be doing it? Isn’t the Captan in this thread also in a powder form?


The Captan in this thread is not powder, but instead WDG (water dispersible granules) and that was the issue. Every online source was posting the weight per ounce of Captan 50 WP (wettable powder) probably because it is, or was, much more common.
I posted the mix rate of Imidan 70 WP, or sometimes called WSB (water soluble bags, which contains wettable powder) in a link from the University of Kentucky above.
The appropriate mix rate is 2.5 teaspoons per gallon water.


Reply to applefan


80 WDG is 80% active ingredient by weight.
50 WP is 50% active ingredient by weight.

So does anyone know of a good accurate digital english/metric scale than can accurately weigh tablespoons?

Weigh a volume of 50WP. Find the amount of
active ingredient then 80WDG and voila!!!.

Until then I am using 2 1/2 tsp of 80 WDG per gallon.



“I just have to get an accurate digital scale so I can use metric. The danger of using dry oz. and fluid oz. intrchangeably is too great.”

Mike, I’m a bit confused as to your concern regarding the weight. The volume measurements I posted from the beginning are not derived from weight or from anything related to Captan 50 WP. It is purely derived from the 80 WDG label based on a concentrate spray of 100 gals per acre, so the weight has been taken into account already. So unless you are uneasy about that measurement method for some reason I’m not sure why you are worried.

When I posted the UK link that was in regards to Imidan, but there was coincidentally measurement data there also for 50WP. I did not in any way use that data for the volume measurements. The data used for that was from the University of Alabama and it was for Captan 80 WDG specifically. There are no translation issues from one form to the other in play with those measurements.
The usage range is fairly broad anyway and I would think that a volume measurement (particularly of the granules which don’t settle) would be as accurate as a weight measurement or at least very nearly so.