I have this idea that if I buy high quality olive oil from non-industrial producers then it doesn't need an "organic" label because olives are pretty resistant and don't require that much pesticide.
Is this correct?
Olive oil degrades over time so freshness is important. Some of the higher priced olive oils sit on shelves for a very long time and by time they are sold they can be of lower quality than some mass produced olive oils.
I'd say you're in the right frame of mind and would recommend finding a brand with a local representative who can trust and know the source and timing of the oil.
Many smaller olive oil producers don't bother with organic certification because of cost, but they have same or better standards. Therefore there is a sweet-spot where you can get quality olive oil similar to organics at decent prices.
Keep in mind good olive oil is produced in many places, including Greece, Spain, and Lebanon. Not just Italy.
"Organic" is not only about pesticides.
Other factors that would prevent something being labelled "organic" include:
It's entirely likely that olives for olive oil have been fertilized with inorganic fertilizer.
It's also not unusual for olive oil (and many other products) to be produced to 100% organic standards, but for the producers to not feel it worthwhile to spend the money and effort required to get certification.
It is not really correct: olives are subject to be attacked and eventually destroyed by different kind of parasites, as for instance the olive fruit fly, one of the most serious pest in the cultivation of olives.
Also, olives tree can be attacked by mushrooms, bacterius, and parasites.
What is true, on the contrary, is that the olive tree is quite resistant to cold weather, and it can go below zero with no substantial damage (depending on the subspecies).
An "organic" label certifies that no chemical products are used, and of course if you want to be completely sure that you are not using contaminated oil, you should avoid completely the posibility that pesticides are being used (= it should have an organic label).
About the quantity of pesticide used... it's really difficult to give an answer: it depends on too many factors: where the olive plants are located, the laws of the country about pesticides, the 'common sense' of the producer.
In this interesting blog post (sorry it is in italian, you can try with google translate) they explain shortly that to have abiologic oil you can in any case use biological treatments (killer insects, biological pesticides and so on) which guarantee that you have no pesticide residua in your oil.
This is the only guaranteed way to have organic oil.