Related Rule
Israel
Practice Relating to Rule 72. Poison and Poisoned Weapons
Referring to Israel’s Law of War Booklet (1986), the Report on the Practice of Israel provides that the Israel Defense Forces do “not condone the use of poison in warfare, irrespective of the method or means of its employment”. 
Report on the Practice Israel, 1997, Chapter 3.2, referring to Conduct in the Battlefield in Accordance with the Law of War, Israel Defense Forces, 1986, p. 11.
Israel’s Manual on the Laws of War (1998) provides:
It is forbidden to poison water sources, arrows or bullets. This is one of the most ancient prohibitions in the laws of war. Already back in ancient Greece and Rome, it was forbidden to use poison which was perceived as “a dishonorable weapon” that disgraces the user. This prohibition has been carefully upheld also into the twentieth century. Another reason for this prohibition is the difficulty in controlling the outcome of the poisoning, with the possibility that it could also spread to an innocent civilian population (for example, the poisoning of water sources that cannot be restricted to military use only). 
Israel, Laws of War in the Battlefield, Manual, Military Advocate General Headquarters, Military School, 1998, p. 12.
Israel’s Manual on the Rules of Warfare (2006) states: “The rules of warfare … include many customs that have become entrenched in warfare over the years, such as … the ban on the use of poison”. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 10; see also p. 13.
The manual further states:
It is forbidden to use poison, for instance to poison water sources, arrows or bullets. This is one of the most ancient prohibitions under the rules of warfare. In Ancient Greece and Ancient Rome, it was forbidden to use poison as it was seen to be a “dishonourable weapon”, bringing shame on the person who used it. This ban has been scrupulously observed in the twentieth and twenty-first centuries. The poisoning of water sources is also prohibited because the results are hard to control and could spread to the civilian population. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 14.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).