It is generally not a good idea to apply pesticides in full sun since it may cause tissue damage.
Chemical damage? or sunburn caused by concentration of solar rays by the optical magnifier effect of the droplets?
Oh and I also wouldnt cut with a hot knife. This isnt a movie where a red hot poker will heal a bullet wound, heat cooks plants.
But it's true, at least for plants and vertebrates.
I've healed spreading flesh eating black spots on my Pedro before with success.
I had also flat cut a
big protrusive congenital melanocytic nevus (mole) on my scalp (the size of a
kidney bean) using a razor blade, and killed the remaining root (composed of proliferating melanocytes) with a red hot knife.
The nevus never grew back, but the hair still grows normal.
========================================Today I spotted REALLY tiny crawling white/cream creatures on my Pedros & Peruvians.
They are so so so small, the size of a needle tip, I cannot even clearly see what they actually are due to the small size.
They walk slowly and rarely, usually standing still and pretending to be dust particles.
What are these critters exactly?
Are they damaging to the cacti?
If so, how can I get rid of them?