A preliminary study of the fauna associated with lucerne, Medicago sativa L., variety Wairau in New Zealand : with special reference to pests, sampling methods and lucerne seed production

Abstract

Insects and other pests of Lucerne in New Zealand have received only spasmodic and cursory attention in the past (see Section 2.1). As a result, basic and applied information on insects associated with lucerne in New Zealand is limited. It is important to make an overall assessment of the fauna associated with Lucerne to overcome the previous deficiency of information, particularly to establish which species are pests (see Chapters 4. 9, 10 and 12). The need for this information becomes more important as the increase in lucerne acreage continues, and realization of the value of lucerne grows (see Chapter 3).

A quantitative survey was considered the best way of making such an overall assessment of the fauna, because it can reveal the abundance and distribution of single species with known precision (see Chapter 6). Pilot sampling for survey purposes can also assist in the formulation of optimal sampling plans for particular species or groups.

The primary aims of this study were as follows: 1. To find out what species of arthropods and other animals are associated with Lucerne in the South Island (see Chapter 7). 2. To attempt a preliminary economic assessment of Lucerne posts in New Zealand (see Chapters 4, 5, and 7 to 12). 3. To indicate optimal sampling plans for the more abundant insects associated with Lucerne (see Chapters 6 and 8). 4. To examine some basic aspects of Lucerne seed production (see Chapter 11). Subsidiary aims to these primary aims are given in Chapters 7 to 11. Obviously with such multipurpose and comprehensive aims it was difficult to achieve conclusive results for all of them. It was felt that such a comprehensive study was best for a preliminary study, because of the absence of knowledge on insects associated with Lucerne and methods for measuring their populations. Consequently, the primary aims were to establish procedures to more specific studies in the future, and to provide on objective preliminary assessment of the fauna associated with Lucerne.

In addition, it was felt that the value and scope of a single plant ecosystem study (see Chapter 2) could be demonstrated in conjunction with the primary aims. Hence a secondary aim of this study was to examine the problems of single crop ecosystem studies (see Chapters 2 and 12).

The author’s philosophy is included in Chapters 2 and 6 because ecosystem studies and preliminary quantitative surveys are still in an early stage of development, so that clearcut methodology and theories have not been developed at the single plant level for associated faunal studies.

The arrangement of Lucerne pests in Chapters 4 and 5, which is partly based on the results of this study, is primarily for agriculturalists rather than the common arrangement based on insect taxonomy, which was used by Pottinger and Macfarlane (1967) in a preliminary review of Lucerne pests in New Zealand. Otherwise, this thesis follows a conventional pattern of introduction (Part I), Review of Literature (Part II), Methods and Results (Part III), and conclusions (Part IV).