Why Did DEET Kill My Strawberry Leaves?

Factual Questions
1

When I was still a child, I had a Strawberry patch in our backyard. I really liked that Strawberry patch, and I tried in my own childish way to nurture and take care of it. Anyways, one day I got a wonderful idea. Why not spray the human bug repellant “DEET” on the plants? After all, it is safe enough to use on humans. It must be safe enough on plants too, no? So, I sprayed it on the leaves. And in what must have just been literally minutes, the leaves developed ominous dark brown patches where the DEET landed! They eventually fell off or had to be cut.

Why would something so harmless to even humans, be so deadly to plants? (I still don’t look at DEET the same way since then.)

Thank you all who reply:)

[BTW, although it isn’t necessary, Cecil Adams could consider this question too. Simply put a “Dear Cecil:” at the beginning of my question, and of course my username after. I mainly want this question answered in this forum though.]

2

I suspect it may have been the solution the DEET was dissolved in, like alcohol. That might strip the natural waxy coating off the leaves, killing them.

3

The basic point is that the physiology of a strawberry leaf is vastly different from that of human skin. For a thought experiment, consider the effect of immersing your finger in alcohol, vs. the effect of doing that to a strawberry plant.

It’s also worth noting that DEET isn’t considered harmless to humans. From this article:

4

Usually methanol IIRC, but I don’t have a bottle handy to check.

5

The leaf surface exchanges gases with the atmosphere. I think a coating of deet spray in your lungs would kill you too.