Methomyl is a white crystalline solid with a melting point of 77 °C and a vapour pressure of 0.72 mPa (25°C ). Its solubility in water is 54.7 g/litre and its octanol/water partition coefficient (K) is 1.24. It is stable in sterile water at p1-1 7, but is broken down at higher pH values, the half-life being 30 days at pH 9 and 25°C.