I have a bag of CAPTAN 80 WDG.
Instructions are only given as “LBS PER ACRE”
How do I convert to either Weight or Volume per gallon?
Thanx
Mike
Well Mike since nobody else is answering. I needed this same info. so I had to look it up anyway.
Captan 80 WDG Mix Rates per gallon water
Since you are in NY Mike I included only those values for fruits east of the Rockies.
Apples: 3/4 - 1 1/2 tablespoon(s) (tbsp.)
Peaches: 3/4 - 1 1/2 tbsp.
Cherries: 3/4 tbsp.
Plums: 3/4 - 1 tbsp.
Strawberries: 3/4 - 1 tbsp.
Blackberries: 3/4 tbsp.
For powdery mildew protection add 1 1/2 tbsp. micronized sulfur and combine with the lower rate Captan of 3/4 tbsp. per gallon water. Do not spray on sulfur sensitive varieties Red Delicious, Stayman, Baldwin, MacIntosh, Golden Delicious, Jonathan or King. Concord and labrusca type grapes should also be avoided with sulfur or sulfur containing spray mixtures.
I derived this from the University of Alabama cooperative extension worksheet.
Since I have multiple varieties and want to mix just one tank mixture I plan to split the difference and spray 1 tbsp. per gallon on everything and just go back over the apples and lay a light mist on top of what was applied in the first pass.
Hey Mike, I should add that I put the stuff about sulfur in there because that’s the advice everywhere so I adhered to it in writing. Having said that I’ve sprayed the Hell out of my Concord grapes (seeded and seedless) and Stayman apples, all other apples and pears dozens and dozens of times with no injury whatsoever.
It may be the case however that combining with Captan may increase the chances of foliage damage. In fact, I’ve read that it does.
I wouldn’t use more than a tablespoon a gallon, although I’m not suggesting that with any more authority than Appleseed’s information- it is just what I came up with when crunching numbers from labels I have.
Captan can burn tender foliage, but tender foliage is created by wet, cool springs which we are not having
Mike, I forgot to include grapes.
Grapes: 1/3 - 3/4 tbsp.
The 1 1/2 tbsp. for peaches and apples translates to the maximum application rate of 5 lbs. per acre for peaches and apples east of the Rockies. The methodology for translation is based on 100 gals. spray per acre which the label (Agri-Star in my case) is in agreement with.
Alan makes a good point about tender foliage and the label provides cautionary statements regarding that under “Compatibility and Plant Safety”. Under these conditions it actually suggests reducing to the minimum rate which would of course, translate to 3/4 tbsp. per gallon.
The mix rate for your Imidan 70WP is listed at 2.5 tsp. per gallon.
When I discovered this thread last night, I was too tired to answer it and planned to do so today, but I see it’s already been answered. Nevertheless, here’s my calculation.
At the 5 lb./acre max rate for peaches (80 oz.) divided by 250 gal./acre for full dilute would equal 0.32 oz. gallon of water. At one time I weighed Captan and found an old post where I noted the volume by weight. At the time I noted it weighed 65% of weight of water by volume. 0.32 oz. divided by 65% would equal 0.49 fluid ounces, or a tablespoon per gallon of water.
The U of Kentucky bulletin Apple linked shows the actual weight of Captan 50 at 77% of the weight of water by volume. If that’s also the same statistic for Captan 80 (and my measurements were incorrect) then that would mean 0.41 fluid ounces of Captan per gallon of water, or about 80% of a tablespoon per gallon.
I don’t use volume measurements, but I would say somewhere between 80% to 100% of a full tablespoon of captan per gallon of water would be about right for a spray to the point of runoff.
Olpea, before discovering Alabama’s worksheet I tried using the methodology you are. The problem is that Captan 80 (being water dispersible granules) has a different weight/volume. The new formulations also include a sticker, so that even further complicates things. I searched high and low and could not find that weight anywhere online, though I’m certain it’s out there somewhere.
Alabama’s methodology seems to be the way to go, and using their worksheet I arrived at figures that were identical to others I had come across with someone else doing the mathematics.
As a side note, I came across an old thread where some food plot guys were using 1/2 - 3/4 cup per gallon Captan 50 WP on their trees , and reporting very good results. LOL…I should hope so. 
Apple,
You make a good point. There are many different variables when it comes to spraying. My airblast sprayer sprays 100 gal./acre but after I run it through the peaches, the foliage feels pretty wet, this despite 100 gal per acre is supposed to be 2.5X concentrate spray. My wand sprayer uses significantly more spray per tree.
I think when using wand or pump up sprayers, one person’s definition of the “point of runoff” is different than anothers. I think it also a lot depends on the size of droplets one is using.
For the record, I remeasured Captan 80 by volume on my scale tonight. I took two measurements, one measured 75% of the volume of water, the other measured 79%, so I would say U of Kentucky’s assessment of 77% is pretty much right on.
I don’t know how I measured it before at 65%, but as I say I don’t use volume measurements to measure pesticides, so the correct figure may not have stuck in my head.
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Interesting stuff Olpea, as always. I actually posted the UK link as a source for the Imidan info, though I did look briefly around in the information. I thought what they had listed for weight was for 50WP, I must have overlooked the 80 WDG. I just thought that being a finely ground powder (that being the 50WP) that the weight would be significantly heavier per given volume than WDG, being larger “beads”, thus allowing more air space to exist between the granules, plus I would guess (maybe incorrectly) that any additive such as a sticker would influence the weight/volume ratio even further.
I understand your measuring pesticides by weight, but for me it just isn’t practical and any very slight difference between weight and volume (assuming correct measurement) would be so miniscule as to be negligible. Plus, I’d have to purchase a scale.
I just cannot imagine how an airblast sprayer could more efficiently apply spray than could be done by hand. I’m not saying I don’t believe you, because I do, it’s just that I’ve watched videos of them being used and they seemed to be wasting spray to me. I spray very carefully, but where I do end up wasting a lot of spray is trying to cover the tops of taller trees. I have a Jap plum that is easily 14’ tall and trying to get decent cover in the top uses more spray than the rest of the tree.
I saw a backpack airblast sprayer with a little Stihl engine on it ($800) and it looked like it worked nice, but appeared to put a lot of product into a cloud and a great deal of it not landing on the intended target.
Thanks for the good advice, it’s always good to get it from a professional.
So, forgive me for being slow here, but are you saying my mix rates are wrong, or are you saying they are right? I posted them from minimum to maximum based on label directives and using the 100 gal. per acre methodology. If you feel I am wrong…in which way, too heavy or too light?
The problem with hand sprayers comes to play with larger, denser trees. An airblast sprays pushes through it all and will cover both sides of leaves quickly and thoroughly. I would agree that a hand sprayer can get more of the material on the target- just not the whole target once trees achieve a certain size.
Even spraying tomatoes with copper takes me a long time with a hand sprayer, having to spray both the tops and undersides of leaves.
Apple,
For my pull behind wand sprayer, I would say the rate is probably a little high. That said, my wand sprayer sprays a pretty coarse droplet size and so uses quite a bit more spray than a pump up sprayer. Because of that my mix is based on 250 gal/acre for full dilute for the wand sprayer.
250 gal./acre is considered full dilute in most spray guides for peaches. It seems to work for my wand sprayer because a full sized peach tree takes about that much spray and my peach trees are planted at 100 trees/acre (100 trees/acre X 2.5 gal = 250 gal./acre). I’ve sprayed trees with a back pack and it takes about half that much spray, so for those types of sprayers, probably estimating 100 gal./acre, as you have done, would be more accurate as a basis for calculations.
Of course one can also estimate the total area of the all the trees canopies planned to be sprayed and put the proportionate amount of pesticide in the tank for the area, but one would still need to know beforehand the amount of spray needed to cover all the trees planned to be sprayed.
I agree with you about airblast sprayers. As you suggest they do move more spray off target. Also agree w/ Alan’s comment, they do a more thorough job placing spray material on all the leaves and fruit.
Olpea, the concentration of spray shouldn’t be higher with a hand sprayer just because it gets more spray on target, seems to me. All that matters in this equation is how much material is reaching the plant. Recommendations are not made based on type of sprayer (except with highly concentrated mist applications).
The only way the measurements might be different, I believe, is if the concerns were environmental as opposed of what’s right for pest control.
But then my brain might be a bit foggy after the five long days of spraying I just completed, which denied me any break at all this last weekend. I’m running on a definite sleep deficit.
Alan,
It’s true recommendations/labels aren’t based on the type of sprayer, nor even the size of the plant/tree sprayed. As you know, recommendations/labels are based solely on the type of crop and land area to be sprayed (They don’t even care about crop density.)
What I was trying to communicate with my above post was trying to extrapolate concentrate spraying on a practical level for folks using just pump sprayers which spray typically spray a smaller amount (i.e. more concentrated amount) of spray material per tree.
When figuring the amount of pesticide to add to my airblast, which sprays at 100 gal./acre at 100 trees per acre (i.e. 1 gallon of spray material per tree) I don’t see the difference between using a one gallon pump up sprayer which would spray 1 gallon per tree (planted at the same 100 trees/acre density) vs. my 400 gallon airblast. In my way of thinking, it’s simply scaling down the recipe. I’ll admit it’s easier to mix in my big sprayer. 400 gal covers 4 acres, so I’d just add 20 lbs. of Captan to a full tank.
My wand sprayer sprays a much coarser spray. To get all the foliage wet it seems like it takes double the amount of carrier (water) with my wand.
So if you are using twice as much water why would you want a more concentrated mix? No matter what you use to spray a dilute mix you are seeking thorough and even coverage to the point of dripping (so you know things are covered). To me that means spraying with the same concentration of materials whether you are using an airblast sprayer or a paint brush.
I never worry about acreage (given all the huge apple trees I spray and also small strangely arranged, mixed orchards) but many compounds provide instructions for both amount per acre and amount per 100 gallons of dilute spray. That ratio seems to usually come to about 2.5 the amount of material per acre as is used in 100 gallons of mix.
Olpea
How does your wand sprayer fit into your spray program with the airblast?
Ok…so in summation, I’ve rechecked my math as well as taken into consideration all that mentioned in this thread. My numbers are correct. I am supremely confident in both my research sources as well as the simple math and the measurements I posted are absolutely correct.
Mike…read the label and consider the variables as with anything, but consider my numbers a correct and direct volume translation of the label directives.
I wouldn’t use a paintbrush for application it would be too slow, and an airblast sprayer would risk overspray in that beautiful trout filled pond you have.
I’m thinking you have some form of pump sprayer like I have. I’m going to use that.
So what type of properly pruned tree are you talking about that is so dense it cannot be adequately sprayed with a hand sprayer? Are we talking commercial applications or BYO stuff here? I’ve yet to see a fruit tree so dense I could not spray it by hand, but I know almost nothing.
I don’t have any issues with coverage, but I have done so much, with so little, for so long, that I can now do almost anything with nothing.
I’m talking about full sized, free standing trees. I don’t mean seedling rootstock, but on average, trees of 14’ height and spread on 106 or 111 rootstock with apples. I just can’t imagine trying to get the undersides of trees with a hand sprayer, although it isn’t necessary with everything you might be spraying.
I really don’t have experience managing trees with a back back sprayer, so my advice is probably not the most useful on variables pertaining to the use of that equipment.
Not that I haven’t spent many hours over the years with one on my back. I still use a hand sprayer to put copper on my tomatoes and it’s a PIA to have to first spray the tops and then come underneath to get the undersides of the leaves.
My captan measurements are what I came up with when applying at the rates recommended by Cornell when it is mixed with another fungicide to attack the same fungus- apple scab.
With Captec (a 38% liquid formulation), in this context, they recommend only one pint to one quart per 100 gallons, which comes to only 16 TBS per 25 gallons at the very highest rate.
For control of summer fungus they recommend only 1 pint per 100 gallons as used alone. That is their only recommended rate in this context.
These recommendations are what are on the Captec label as well.
Alan,
I’m not sure what you mean here. I don’t use a more concentrated mix w/ twice as much water. The opposite would be true. One would want to dilute the concentration by half w/ twice as much water.
I agree with you, if the spray is really a full dilute and all the foliage is sprayed equally to the point of runoff. That would produce a consistent result every time, which would necessitate the same ratio of water/pesticide every time, regardless of the equipment used.
My point is that when I spray with some type of pump up sprayer, I really don’t spray all the foliage to the point of runoff. To be frank, I’m coating the upper part of the canopy completely, but everything underneath isn’t covered very good. I’m really depending on the rain to redistribute the pesticide to the dense part of the canopy. I think this is probably true for most people using pump up sprayers with full sized trees, unless they are taking a tremendous amount of time to spray each tree, in which case they are going to use more spray. If they are using more spray, then they truly are spraying a full dilute and would adjust their calculation based on a full dilute. But if they are only using about a gallon of spray per tree, they are really spraying a concentrate spray, not a full dilute.
As you say, it’s really not the equipment which matters, but practically speaking the equipment for backyard growers really defines how much of a concentrate spray most people spray.
To me, I can’t see how someone could truly be spraying all the foliage front and back w/ one gallon of spray on a full sized tree. I’m referring to a tree with a 20 foot diameter canopy. Trees that size can’t be planted any closer than 100 trees/acre, which means 100 gallons of spray/acre, which by definition would be a concentrate spray.
Perhaps I shouldn’t have mentioned different types of equipment. The real issue is how much one is spraying on a full sized tree. It’s just that in past discussions people have mentioned they spray about one gallon (or less) on a full sized tree. I do the same w/ pump up equipment. One gallon/tree is a concentrate spray, regardless if people think they are spraying to the point of runoff.
Blueberry,
I have a larger orchard (now up to about 450 trees) and a small backyard orchard I started with. My backyard orchard only has about 50 trees. I use a pull behind wand sprayer for those.
Those who joined the various fruit forums the same time I did (or before) know I’ve sort of cataloged this evolution from a backyard grower to a commercial orchard. I started out spraying my backyard trees with a pump up sprayer, then went to backpack, then went to a pull behind wand sprayer. Obviously, a wand sprayer would take too long to spray the larger orchard. In fact, I can spray my larger orchard faster w/ the airblast, than I can my small backyard orchard with a wand.
I still use a power wand sprayer in the large orchard, but mostly just to spray weeds. Of course I use a different sprayer than the one used to spray the backyard trees. You want to use a different sprayer for herbicides vs. insecticides. IMO, it’s too hard to really get all the herbicide washed out of a sprayer, or effectively neutralize the herbicide.