MERPHOS

Merphos is an organothiophosphorus compound used as a defoliant but the active ingredient is no longer contained in any registered pesticide product in the US and in EU. Therefore, Environmental Protection Agency (EPA) is characterizing it as canceled.
The status of merphos in the EU pesticide database is ‘Not Approved’ under the Regulation EC 1107/2009 and not authorized at national level in EU countries. However a maximum level of residues (MRL) is regulated in foods as the default MRL of 0.01 mg kg-1 according to Art 18(1)(b) Reg 396/2005.
Merphos was used to defoliate cotton at application rates of 1.1–2.2 kg active ingredient per acre and can induce leaf abscission in some other plants, such as roses and hydrangeas. It was particularly suited for total defoliation of cotton preparatory to machine harvesting because the natural action of the substance causes the leaves to drop in a relatively green state with fresh weight adequate to cause them to fall to the ground.
The technical product used to have 95% purity. Formulation used to contain 720 g active ingredient per liter or being an emulsifiable concentrate containing 6 lb per gallon.