When was the first verified incident of planned germ warfare anywhere in the world?

During the 6th century B.C., the Assyrians poisoned enemy wells with a fungus that would render the enemy delirious.

In 184 B.C., Hannibal of Carthage had clay pots filled with venomous snakes and instructed his soldiers to throw the pots onto the decks of Pergamene (western Turkey) ships.

During the Middle-Ages (5th century-15th century) the Mongols, Turks and other groups used infected animal carcasses to infect enemy water supplies. Prior to the bubonic plague epidemic known as the Black Death, Mongol and Turkish armies were reported to have catapulted disease-laden corpses into besieged cities

1400-1800 A.D. The Native American population was decimated after contact with the Old World due to the inadvertent introduction of many fatal infectious diseases.

1914-1918 A.D. Then there was the use of gas and other chemical weapons by both sides during World-War I.

During the Sino-Japanese War (1937-1945) and World War II (1939-1945), the Special Research Units of the Imperial Japanese Army, such as Unit 731, conducted human experimentation on thousands of Chinese, among others. In its military campaigns, the Japanese used biological warfare on Chinese soldiers and civilians. This employment has been largely viewed as ineffective due to inefficient delivery systems. However, firsthand accounts testify that the Japanese infected civilians through the distribution of plagued foodstuffs and newer estimates suggest over 580,000 victims, largely due to plague and cholera outbreaks.

In response to suspected biological warfare development in Nazi Germany, the U.S., U.K., and Canada initiated a biological warfare development program in 1941 that resulted in the weaponization of anthrax, brucellosis, and botulism toxin. (Fear of the German program turned out to be vastly exaggerated.)

Today, according to the U.S. Department of Defense, more than ten countries are suspected to have continuing offensive biological warfare programs, including Russia, Israel, China, Iran, Syria and North Korea. Offensive biological warfare programs in Iraq were dismantled after the first Gulf War (1990-91). Libya dismantled and disavowed its biological warfare program in 2003. The fate of the vast network of clandestine sites comprising the old Soviet biological warfare program, as well as its many tons of weaponized smallpox, remains undocumented.

The Turks catapulted infected bodies into Vienna during the siege in 1683.

the huns launched infected bodies into a city

hiro shima is the first (and ironically the last) massive biological warfare, the above answer is the first one ever.

P.S. no offense but saying "germ" makes you sound like such a pussy