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Asked by galilsoilfarm ·September 23, 2018 ·24.5k readers

Papaya Leaf FPJ as a BioPesticide

Papaya leaves contain papain, a proteolytic enzyme which is a naturally occurring bio-pesticide. As such I was wondering if could apply Papaya Leaf FPJ as a pesticide?

The answer

Drake Weinert Foundation · Sep 24, 2018 ✓ Marked as the answer
The process of fermentation eliminates many of the pesticide type functions when making KNF Food. In fact, many things that are known poisons are made edible after fermentation has elapsed, so I am very skeptical of the papaya leaf KNF Food being an effective pesticide. You may find it works, but in my best understanding, it acts as a food to stimulate good biology rather than killing or inhibiting something you want to eliminate. I have made KNF Food from papaya leaves and it was quite tasty, though I prefer to make it from the fruits for my purposes. If you are looking for an effective way to get the proteolytic enzyme from papaya leaves, perhaps consider putting them in a pressure cooker with water and cooking them for many hours until the water reduces in half. This dark slurry is then strained and combined with liquid soap to become an effective pesticide.

From the KNF library

From the KNF library Drafted by Claude from Office Hours and the books · Sep 2026 · 5 sources

Drake recommends testing before you count on it. An Office Hours answer says a fermented plant juice from tobacco leaves "may act as a pesticide," and that it is harsh enough to need gloves. (Office Hours Ep. 17, 45:57)

Fermentation can strip a leaf's harsh compounds. Rhubarb leaves hold about 5% oxalic acid, and fermentation breaks it down. (Office Hours Ep. 122, 41:52)

If you ferment papaya anyway, gather the tips, unripe fruit, flowers, or ripe fruit. Mature leaves just make sugar. (Office Hours Oct 2025, 15:04)

Go easy on the sprayer. Too much fermented plant juice adds nitrogen, drives overgrowth, and makes plants more attractive to pests. (Office Hours Ep. 126, 39:37) For caterpillars on kale, the library's answer is calcium to harden the leaves. (Office Hours Ep. 74, 11:38)

The library does not say whether papaya leaf FPJ kills or repels any pest. It says nothing about papain.

Sources

1 more answer
josewalkertwd · Dec 16, 2021
Hi, searching about the extraction of papain, I found that you can scratch the skin of a green papaya with a knife (Not taking out the green papaya) to extract the papain, the process is repeated every 2 weeks and Mature fruits are discarted (may be used for some fpj or compost) , this will greatly decrease the production of papaya in this plant. For papain dilution mix it with water and use a filter, I haven’t tried it , maybe I’ll try it this week and let’s see what happens! that’s were I found it Peace ✌️ https://repositorio.uniandes.edu.co/bitstream/handle/1992/23586/u303039.pdf

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