Some people believe the opposite:
The legend goes that young snakes have not yet learned how to control the amount of venom they inject. They are therefore more dangerous than adult snakes
although it’s possible that this legend is true and baby snakes are more dangerous than adults because they haven’t learned to control the amount of venom they inject when they bite, it’s safe to say this is unlikely to be the case. Due to the complexities of the original question, I doubt this statement will ever be tackled in a manner that sufficiently addresses all of its assumptions. But until then, try not to get bitten by any venomous snakes, no matter how old they are.
From Are Bites from Baby Venomous Snakes More Dangerous Than Those From Adults?
An excerpt froma book authored by William K. Hayes, Department of Earth and Biological Sciences, Loma Linda University, Loma Linda, CA 92350 USA.
Another article examines the myth that young snakes are more dangerous:
When [young] snakes
bite, they typically bite hard, pumping the attacker full of every last bit of venom. If a young venomous snake’s bite were to
be more dangerous than an adult’s, this would be the only way.
Ernst, Carl H. 1992. Venomous Reptiles of North America. Smithsonian Institution Press, Washington, D.C.
Mehrtens, John M. 1987. Living Snakes of the World in Color. Sterling Press, New York, New York