Delta-8-THC is a minor cannabinoid, occurring in the plant in very small concentrations. Delta-8-THC is also known to be a degraded form of THC, and is not directly produced by cannabinoid-synthesizing enzymes within the plant. When THC is stored for a period of time, it degrades into delta-8-THC. Commercial growers and extractors use selective breeding and molecular isolation to access greater quantities of delta-8-THC. 

Read more about Delta-8-THC here: https://weedmaps.com/learn/dictionary/delta-8-tetrahydrocannabinol/