There are markings on D18. You are in a better position than us to be able to read those markings.
C37 is ceramic filter capacitor, 100nF is a commonl value.
The panel is fitted to a set of hydraulic farm scrapers. It controls the drive motor for hydraulic pump and also individual solenoid valves for ram controls plus proximity sensors for shutting scrapers down when scrapers have finished.The diode and cap are on the part of the board for the control of these solenoids and proximity switches.Tell us a bit more of where the board is from and what it is supposed to do.
Test the good diodes with the diode check on your DMM and tell us which way the current is flowing.
Any common 1N4001-1N4007 diode should work.
Lane 4 had a power spike and burnt one end of diode from board and also one end of the cap.As far as I can tell, the 16V line supplies power to the Lane Limit Switch. The diode is just for protection.
Any SMD rectifier diode should work. You may want to check the dimensions of the diode on the board.
What is your estimate of the dimensions of that diode you see?
How do you know that the diode is bad and needs replacing?
Here is an example of a rectifier diode:
http://uk.farnell.com/taiwan-semiconductor/s1bl/diode-sgp-1a-100v/dp/1559149?MER=mktBestSellerA