Scientists at Israel’s Technion Institute have developed a program and algorithm for estimating the fruit content of an apple tree. The program searches nighttime photographs of illuminated apple trees, counting glints in the foliage from light reflecting off the shiny fruit.

http://pard.technion.ac.il/2015/09/06/new-year-is-time-for-apples-and-honey-smart-ways-to-harvest-from-technion-israel/

https://www.newscientist.com/article/mg22630212.100-robots-can-count-apples-on-a-tree–as-long-as-its-night/#.VWq4QNKqpBe

http://www.sciencedirect.com/science/article/pii/S016816991500112X