[Todd Parlo]

Apple Scab Fungus Disease is a fungal disease produced by the fungal pathogen venturia inaequalis. It affects the fruit and foliage of apple trees.

[Osier Farm]

I read that using urea on apple leaves (at the end of the season) can help break them down and prevent apple scab for the next spring. Can urine be used instead, and if so what kind of concentration should I use?

[Todd Parlo]

Ah, this is a subject near and dear to my heart (or maybe other regions of the anatomy). I had a client ask a related question just this week. We will have this in animal waste and bedding, but I’ll take a guess and assume you mean human urine. The safe route is to keep it in that 10-15 % (water to urine) proportion for spray applications. Now, we all know looking at the color intensity in the toilet bowl how much concentration of constituents can vary so remember this is not a standardized product. Here, however we are not really talking about foliar spraying midseason leaves, or even soil fertilizing but rather leaf breakdown. My opinion is that there is an impasse. You want to get that c-n ratio working for you which means as much nitrogen as possible (the urea/uric acid content) but the more you add the more you are likely to lose from leaching. Doubly worse if vegetation has been winter killed in the ground layer, and this highly soluble product will head south. The real issue is that you are going to run out of urine faster than you would like, despite a human being capable of turning out a respectable 75-200 gallons of the stuff each year. Which most of us incidentally (and pun intended) piss away every year. The Scandinavians have us well beat on the intelligent use of waste by the way. Back to topic though, it makes sense to repeatedly hit the material with a wash if you have the time, and better yet make it part of a program to compost the debris. Spraying in the canopy is likely going to lead to some N blowoff too, ground application less, and when covered with mowings, mulch, etc. soon after, the least. The go-to commercially is of course urea, but certified organic producers are disallowed this one. As for timing, growers in cold climates should be careful to treat late enough in the season to thwart any regrowth or dormancy interference from a nitrogen hit. For those intrigued about the peetenial of this resource you may want to check out the Rich Earth Institute here in Vermont.