The Citrus Trade History is colourful and a popular topic. I will NOT regurgitate here what has already been written elsewhere. And - I will be happily providing you with links to the quality contributions I have identified in my research.
What I will do though, is to comment on citrus and their trade history from a Meta perspective...
Citrus have been around mankind since around 300 B.C. By that I obviously don't mean Californian Navel oranges in their natty merchandise attire as we are used to today. The experts suggest that the Citron took that honour.
The Citrus category is sufficient in size and clearly intertwined with the development of the human race to an extent that academic scholars were interested enough to go digging. Thus we know that the Chinese knew oranges in the time of Emperor Da Yu and suspect that the Egyptian pharao Tohotmas III knew citrons. References to citrus fruit can also be found in the Bible and early Arabian texts. What all this adds up to is that citrus fruit have been traded for around 3000 years somewher in the world - as any agricultural commodity successful grown was traded one way or the other!
From a modern European perspective, the commercial history of Citrus can be traced back to the beginnings of the 16th century, particularly, the sweet orange.
Today, the Citrus Trade is not only more diverse than it used to be in days gone by, but it has in my view some additional fascinating aspects which make it that much more complex than the other key fruit trade sectors, including bananas.
For starters, citrus is commercially grown in many more countries. Then there is the fact that fruit is typically shipped in a ripened stage; and just look at the huge variety of citrus we consume! Then there is the trade in orange juice concentrate. From a consumer's perspective, citrus more so than any other particular fruit is associated with keeping in good health through the Vitamin C connection.
The Internet is full of country specific essays on citrus trade history, related, for example to Cuba, Morocco and Israel. And for US related Citrus Trade History data, as well as a global overview, the USDA site will be very helpful.
For a comprehensive historical overview I recommend History and Development of the Californian Citrus Industry.
Trade History Of Popular Fruits & Vegetables