In a mature etrog, the bud on the nose of the fruit that appeared before the fruit grew, is called a pittom in Hebrew.
If it is to be considered kosher, an etrog must be without blemish. If the pittom falls off naturally, the etrog is still kosher; if it is knocked off, then the fruit is considered to have a blemish and it is not kosher. An etrog with an intact pittom is more desirable and therefore commands a higher price than does a kosher etrog that has no pittom. For some reason, etrogim from Morocco usually retain their pittoms, but those from Calabria rarely do.
My employers therefore invested time and money into finding ways to make Calabrian etrogim keep their pittomim, hiring professors of agriculture to study the problem. After several years of trial and error, and especially error, my employers broke the pittom barrier.
The experts developed a system that keeps the trees under cover in such a way that they get the sunlight and heat they need, but whose covers do not allow them to lose moisture. Clean spring water is also piped for irrigation purposes. It seems that the pittomim were dropping off because they became dry. Preventing this dryness saves the pittom and raises the quality of the etrog.
A perfect example of how modern agricultural methods serve ancient religious customs.