USDA Organic refers to a standard of growing and distributing produce that has been handled much as has been described above. The term was kind of hijacked by Big Ag as it was being developed, so there are some loopholes. From what I understand, it’s something like 85% towards what one might think of as “pure” organic.
Oregon Tilth Certified Organic is a stronger standard and significantly more “pure,” although I don’t know specifics.
There are some spray pesticides that are USDA Organic compliant, but I’m not sure how that works. I just know they exist.
Also, USDA Organic has some application in the distribution chain. For example, produce has to be warehoused and displayed for sale in USDA Organic certified spaces. If they are mislabeled or mixed with non-organic produce, they can no longer be sold as USDA Organic.
Foods/producers grown outside the U.S. can also be certified USDA Organic, FYI.
—- Forgot to mention that the food has to be grown on land that is free of pesticide use. If a grower is seeking certification on land that had seen pesticide use then it is usually referred to as “transitional,” and must wait out a period of a few years of pesticide-free production.
One example of pest control: a grower I know uses plastic sheeting to heat the ground temperature a few degrees. This allows him to plant squash earlier than the typical growing period. The effect is that he is harvesting squash before the squash bug larvae hatch and start feeding on the plant. (Oddly, they go for the plant and not the squash itself.) Since he’s already harvested the squash, he doesn’t care if the plant goes. Then, once the larvae have done their thing, they’re essentially done for the season, so he’s free to plant more squash without worry.