Not sure of the motivation for BASF to stop making it. Logic says that there wasn't enough demand. I haven't talked to any of the chemist types at Interlux or Pettit but they all were giving the same story of not enough demand for them (BASF) to keep on making it.

I've been curious if there is a background story here and not that I will get a straight answer or an answer at all I just filled out the form on BASF website for questions.....I'll let you know if I hear anything

This is from the BASF site:

Why use Irgarol®?(nl)BASF Irgarol is a highly specific and effective inhibitor of photosynthesis. This makes it ideal, combined with its very low water solubility, for use in long-life antifouling coatings for marine applications to prevent the growth of algae.

Fouling can significantly increase water resistance to boats which can result in up to 40% higher fuel consumption. Fouling can also decrease maneuverability (a safety hazard) and it can damage the ship’s body. In the process of fouling, algae form a substrate for macro-fouling.

While Irgarol shows outstanding performance in the control of algae, it has comparatively low biological activity to animals in general, including fish, shellfish, and humans. It is therefore an ideal active substance for the formulation of biocide packages with a designed performance profile, where it is combined with other active ingredients to control additional target organisms.

Irgarol may also be used as the sole biologically active ingredient in coatings for mariculture devices such as fish nets or oyster racks [i/](nl)