Decline of tree lupin (Lupinus arboreus) on Kaitorete Spit, Canterbury, New Zealand, 1984-1990

Abstract

The decline of a large stand of tree lupin (Lupinus arboreus) at Kaitorete Spit was observed between December 1984 and May 1990. Originally a healthy population, the stand was defoliated by larvae of kowhai moth (Uresiphita polygonalis maorialis) in January 1985 and virtually all plants were killed. As populations of the herbivore declined through larval starvation, the tree lupin partly recovered in 1986. In May 1987, the stand was again devastated, but by disease, probably caused by the fungus Colletotrichum gloeosporioides. The stand partly recovered by May 1989, but repeated attacks have virtually eliminated the tree lupin from its original area. In 1990 tree lupin survived only as short-lived individuals that established around the margin of the infected area before being overwhelmed by the disease. It is considered that the plant has an uncertain future within the area.