Thus in the early 20th century, the U.S. War Department (i.e., the Army Corps of Engineers) tested various means of eradicating the plants, including the jet-streaming of steam and hot water, application of various strong acids, and application of petroleum followed by incineration. Spraying with saturated salt solution (but not dilute solutions) effectively killed the plants; unfortunately this was considered prohibitively expensive, and the engineers selected Harvesta brand herbicide, whose active ingredient was arsenic acid, as the optimal cost-effective tool for eradication. This herbicide was used until 1905, when it was substituted with a different, white arsenic based compound. An engineer charged with the spraying did not think the poison to be a matter of concern, stating that the crew of the spraying boat would routinely catch fish from their working areas and consume them. However, spraying had little hope of completely eradicating the water hyacinth, due to the vastness of escaped colonies and the inaccessibility of some of the infested areas, and the engineer suggested that some biological means of control may be needed.