Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Director's Report.

Abstract

The conditions in Hawaii in 1918 with regard to insect pests were more favourable than during the previous years. This was chiefly due to the effectiveness of imported parasites, of which Scolia manilae is now well established in the fields and has considerably checked the ravages of the larvae of Anómala. Three colonies numbering a total of 19, 833 adults of this parasite have been liberated during the year. The species of Tiphia, Prosena and Dexia liberated in 1916 and 1917 do not show any signs of becoming established, and the same may be said of a large Carabid beetle from Japan and of Tiphia lucida from the Philippines. Dolichurus stantoni, of which about a dozen pairs were liberated in July and September 1917 to destroy cockroaches, is now found in abundance on cane trash and it is thought to be breeding on PTiyllodromia hieroglyphica, and Loboptera extranea. With the exception of a few plantations the damage from leaf-hoppers [Perkinsiella saccharicida] has also been greatly reduced. Observations were made to estimate the percentage of parasitism in different regions, and the results were very variable A high percentage of parasitism does not necessarily mean successful control of the pest, as it usually occurs when, owing to favourable conditions, the numbers of eggs laid by the leaf-hoppers is greatly increased. The artificial distribution of Paranagrus [optabilis] and the Formosan species of Ootetrastichus is being continued on a large scale, amounting during the year to 78 colonies with a total of 29, 010 adults of the latter. Owing to the establishment of Ootetrastichus in the field, rearing of this egg-parasite in cages has been discontinued. Other leaf-hopper enemies include a fungus, Entomopthora sp., which is responsible for the destruction of great numbers, but is unfortunately very difficult to handle in culture, and attempts to grow it artificially have failed. In the course of the discussion following the reading of this report, it was stated that the cultivation of the variety of sugar-cane known as H109 is largely replacing that of other varieties on the Island, but its chief disadvantage is the attraction it has for leaf-hoppers, although these insects do not cause serious damage unless their attack is combined with eye-spot disease. To increase the resisting power of the cane, Mr. Swezey suggested planting as early as July, and it is probable that fertilizers are better withheld during the first summer, especially if early planting has not been possible. The damage from cane-borer [Rhabdocnemis obscura] was very small in comparison with previous years, the Tachinid parasite [Ceromasia sphenophori] now being well established. The cane aphis appeared as usual in many places, and although its ravages are not to be compared with a leaf-hopper outbreak, it is strongly recommended to attempt the introduction of more natural enemies of this pest. Nematodes do not cause serious damage to sugar-cane, although the stunted growth of the Lahaina variety may be partly due to their action, but they have been found infesting other crops such as potatoes, beet, etc., in much greater numbers than in previous years. The Italian lupin and a variety of" beans greatly encourage the spread of this pest.