Calculating pesticide use rates

Asked August 5, 2016, 7:48 PM EDT

I'm trying to calculate how many square feet an ounce of fungicide will treat.

I have a fungicide with a label that instructs the user to apply the fungicide at a rate of 1 pint per acre, using enough water to cover the upper and bottom parts of the leaves on the plants. The label also sais that it typically takes 25 - 100 galllons of water to cover an acre of planted vegetables.

I know an acre = 43560 sq ft. The fungicide has a use rate of 1 pint per acre.

To calculate at the rate of 1 pint per acre:

16 oz = 43560 sq ft --> 43560 / 16 = 2722.5 sq ft. --> 1 oz = 2722.5 sq ft

So, 1 ounce of fungicide concentration will treat 2,722.5 square feet.

Does this calculation look correct?

Also, how do I determine how much water to use? It seems that the label is concerned with how much of the fungicide concentration is used in relation to the area of the crop being treated, assuming it is diluted with enough water to properly wet the the plants. Do I just make an educated guess as to how much water to use for diluting the fungicide?

I greatly appreciate any help you can provide.

Thank you...

Denton County Texas

3 Responses

There’s nothing in the world quite like “sprayer math!” Interesting approach that you have started with. Normally, I first determine the square feet that I will be treating and calculate how much to mix in my tank. ((The square feet of the treated area/43560) *(the rate of pesticide applied on a per acre basis))= amount to spray on the small acreage

Your calculation appears to be correct, but I think you’ve taken the “scenic route” to arrive there. Using your calculation, it would appear that you need to mix this fungicide with approximately 1.6 to 6.25 gallons of water to treat this 16th of an acre. Personally, I like to work backwards from how many square feet I have to treat so that I don’t have any extra pesticide left in my container.

As always, read and follow the labeled directions as the label is the law!

Sprayer math is always fun (and somewhat confusing if you aren’t well versed in it)! If you run in to questions, please don’t hesitate to contact me at the numbers below.

Kind regards,


Thank you!

Anytime. That's what we're here for!