The biological control of noxious weeds

R.M. Johnston was honoured in a lecture read by R.J Tilyard in which it was claimed that the most striking achievement of that time was the immense field of research covered by the biologists of that time.
The great credit of inaugurating work on the biological control of Noxious Weeds must be given to that extremely progressive body, the Hawaiian Sugar Planters Association, and their very capable entomologists.
The plant Lantana camara, originally introduced about the year 1860 as an ornamental shrub, soon began to take possession of large areas of land in the various islands of the Hawaiian group, just as it has done over large tracts of similar land in the warmer portions of Eastern Australia.
The well-known entomologist Koebele, while collecting in Mexico in 1898, noticed that the seeds of this planrt in its native state were damaged by insects which bred in them. This suggested to him the idea that the profuse seeding of the plant might be checked, or even completely prevented, if these insects could be firmly established on the weed lantana in the Hawaiian Islands. Four years later, his idea having been officially approved, he again visited Mexico, and this time made a thorough study of all the insects that feed on lantana. More than twenty different species of these were shipped back to the Chief Entomologist, Perkins, in Honolulu, and eight of these were soon successfully established on the island of Oahu, of which Honolulu is the capital. Of these the most important were the species that prevent the seeding of the plant. The larvae of an Agromyzid fly, Agromyza lantanae proved to be the most effective of these; it attacks the berries before they are mature, and causes them to shrivel up, destroying the seeds within them.
The Butterfly larvae feed chiefly on the fiowers, and are therefore also of great value in preventing the formation of the fruit.
The result of these introductions was a very marked decrease in the amountof infestation by lantana in the drier parts of the islands. With the aid of some judicious mechanical clearing, these parts have now been rendered safe for all time from being overrun by this dangerous weed.