From 1948 - 1967, the city of Jerusalem was divided. Jordan and Israel were officially at war. Apparently though, both the Jordanians and the Israelis were also at war with the bug infestations of Jerusalem's pine trees and at times cooperated to make sure they didn't spread. This document, dated from 1961 and part of a slightly longer correspondence, details how that went. On April 25, at 10 o'clock in the morning. four Jordanians met two of their counterparts from "the other side". The "other side" informed the Jordanians that it was importing a new, under-development pesticide, and they would let them know how it worked. They also asked the Jordanians for information about the insects in their forests so they could do tests and share the results with Jordanian agricultural advisors.
Israel State Archives, MGA 39/9