Black nectar

Black nectar is a type of nectar that is often detrimental to Pikmin but can have other uses.

=In fanon games=

In Pikmin 2... Again?
Spoiled nectar is an aged nectar in Pikmin 2... Again?. It looks similar to normal nectar but has a purple tint. It has a chance to come out of nectar eggs, and if a Pikmin drinks it, its current maturity will regress to the leaf stage. If a leaf-stage Pikmin drinks spoiler nectar, nothing will happen. If a Swarming Sheargrub drinks spoiled nectar, they'll be damaged.

In Pikspore
Black nectar is a type of nectar in Pikspore that reverts the maturity of a Pikmin that drinks from a blob of it to the leaf stage. Certain enemies utilize this horrible goop and it is sometimes left behind by enemies like the Gulagg after defeat. Black nectar can be destroyed by Black Pikmin, the only Pikmin immune to its negative effects. When leaders touch black nectar, it sticks to them, gradually draining their health and slowing them considerably, but it can be removed by rapidly twirling the control stick.