The tropical American shrub Clidemia hirta (Koster's Curse) has become a pest in pastures, cropland, and forests, where it has become naturalized in many parts of the humid tropics. It has spread through the island of Oahu, Hawaii, since 1941, despite attempts at biological control by the introduction of the parasitic thrips, Liothrips urichi, which had proven effective in supressing growth of this noxious weed in Fiji.The pest has colonized habitats similar to those occupied over its natural range—such as forest clearings, trail-sides, and burn-sites. In addition, in Hawaii it has intruded into the understorey of forests which were formerly free from exotic weeds. Fears are held that the resulting ecological disruptions may place further stress on the frail island ecosystems and cause plant and animal extinctions while producing other management and aesthetic problems.Immediate action is necessary to eradicate small colonies of Koster's Curse that have become established on near-by islands, and recommendations are made regarding efforts needed to devise means to control heavy infestations in the highly inaccessible mountains of Oahu.

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Lysimeter soils under 41-yr-old stands of chaparral species and a pine (Pinus coulteri B. Don) were studied to determine the biotic influence on soil morphologic development. The large (5.3 by 5.3 by 2.1 m) unconfined Iysimeters at the San Dimas Experimental Forest in southern California were filled in 1937 with homogenized fine sandy loam soil material derived from diorite. After a 9-yr stabilization period, the Iysimeters were planted with monocultures of species common to California chaparral ecosystems. The species represented, each on a separate Iysimeter and its surrounding buffer zone, are scrub oak (Quercus dumosa Nutt.), ceanothus (Ceanothus crassifolia Torr.), chamise (Adenostoma/asciculatum Hook. & Arn.), and Coulter pine. The soils were described and sampled in triplicate in 1987. Differences in earthworm (including Aporrectodea trapezoides Duges and Allolobophora chlorotica Savigny) activity were related to plant species and played a major role in differentiating the soils. Earthworm activity under scrub oak and ceanothus produced A horizons (7 and 2 cm thick, respectively), composed largely of worm casts, that were darker and enriched in clay compared with underlying C horizons and archived fill material. Earthworm activity was minimal under chamise, and relatively little morphologic development was apparent. The soil under pine, where earthworms were absent, had a clay-depleted A horizon (1 cm thick) and Bt horizons with sufficient clay increase, iIIuviation argillans, and thickness to qualify as an argillic horizon. Mixing and sorting of soil by earthworms has acted against argillic horizon development under the other plant species.

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