Some studies on the use of alginates for the placement and controlled release of diquat on submerged aquatic plants

Viscous solutions of sodium alginate can be extruded under water in the form of a string which will stick to weeds. The sodium alginate reacts with calcium ions to form an insoluble gel of calcium alginate so that the strings become more firmly attached to the weeds. Diquat dibromide can be incorporated into the alginate and this is slowly released into the water close to the plants. Two experiments are described in which this technique is tested in a fast-flowing river and for localised control in a lake. Diquat dihromide was found to be effective, when formulated with alginate, on Ranunculus spp. in the river and Groenlandia densa in the lake.