Preliminary investigation of the diseases of willows (Salix spp.)

Abstract

Willows were introduced into New Zealand by the early European settlers (van Kraayenoord, 1968a). Several species and hybrids have become naturalised and are usually found growing by riverbanks or in other moist situations. The use willows and poplars to control erosion on the steep country and highly erodible soils frequently found in New Zealand, was first implemented during the early days of settlement of the Colony (van Kraayenoord, 1968a). Willows now play a significant role in erosion control, particularly in the South Island catchments, the central North Island pumice country and East Coast North Island papa country. With the extensive use of willows in riverbank and erosion control New Zealand, the disease factor could play a significant role, especially in those areas where planting of a single species has been adopted. The main object of this investigation was to study stem and leaf diseases of Salix spp. incited by micro-organisms and may be summarised this:- (1) To carry out a survey of the extent and severity of the disease factor in New Zealand. (2) To isolate, study in culture and prove the pathogenicity of organisms considered important in the death and dieback of willows. (3) To describe and identify the causal organisms. (4) To determine if possible, factors influencing the spread and degree of infection of the diseases.