the porphyrin molecule favours the anchoring of the porphyrin itself to the lipid domains of cell membranes in the target organism increasing the stability of the complex between the photosensitising agent and the target organism in a further preferred embodiment porphyrin c 12 and porphyrin c 14 frontier scientific usa were used in the composition of the present invention a suitable carrier irrespectively of being a synthetic or natural carrier should have the following the characteristics chemical properties capability to establish a stable non covalent association with porphyrins by means of the presence of negative or positive charges assuring the electrostatic interaction with the positively or respectively negatively charged groups in the porphyrin molecule moreover thanks to the presence of the hydrophobic aromatic macrocycle porphyrins can associate with the core of the polymer chain by hydrophobic interactions physical properties capability to remain stably associated with porphyrins in water over a broad range of physical and chemical conditions such as temperature below 50 u00b0 c and ph 5 0 to 8 0 reflecting the conditions of natural breeding sites as well as in dryness such as temperature below 50 u00b0 c relative humidity up to 80 reflecting the possible extreme storage conditions capability to remain stably associated with porphyrins for at least 6 months in storage conditions and for at least 2 weeks in water biological properties capability to produce once loaded with porphyrins a residual larvicidal activity of up to 2 weeks palatability by mosquito larvae and competitiveness with natural occurring organic matter usually eaten by larvae diameter between 5 u03bcm and 50 u03bcm capability to reach a homogeneous distribution in defined zones of the water column specifically in relation with the larval feeding behaviour of the various species of mosquito.