If you have a small problem in the garden or around the house, you mix a small batch of chemicals to rid your property of the malady. A larger problem is solved with gallons of pressureaided spraying, either by you or your gardener.
If the problem is widespread enough, the local crop duster force is engaged.
What does this parallel? The incessant spraying of our skies by high flying planes.
No, they are not jet contrails. Water vapor from jets vanishes in a short time with the fuels used today....