A target insect in a tidal area is controlled by: choosing a treatment area in a tidal area; selecting an appropriate control agent; determining an appropriate depth below the surface of the treatment area for the delivery of the control agent; determining an appropriate application rate; and delivering the appropriate control agent to at least a portion of the treatment area at the appropriate depth and at the appropriate rate. Treatment may be directed at the larval stage of the target insect with the treatment area between a mean lower low tide demarcation and a mean higher high tide demarcation. The control agent may be delivered through passageways extending along a plurality of downwardly and rearwardly extending agent delivery knives.