Control

Control of possums, when declared a pest on rateable land, is the responsibility of local Pest Destruction Boards. These Boards are elected by local ratepayers, and they employ staff to carry out control operations. Finance for this work normally comes from rates from farmers (and a 1:1 government subsidy).

Methods used to control possums on farmland are many and varied (Anon 1966). Probably the most common methods are the use of phosphorus (jam) and 108Q (jam and carrots). 1080 is probably the most effective but is not favoured in certain areas because of the risk of poisoning domestic animals, particularly farm dogs, from secondary poisoning. Individual Board operators have usually evolved techniques applicable to their particular area. Wherever possible, they make use of local features, such as laying poison around pine trees in spring or feed crops (e.g. turnips) in autumn/winter. The need to maintain full-time employment of staff means that seasonal use is often made of page 201 several techniques and that staff are usually involved in rabbit Oryctolagus cuniculus control as well. To estimate the cost of this control, it would be necessary to separate the various costs in Pest Destruction Board records.

Existing techniques used by Pest Destruction Boards appear to be adequate to reduce local possum populations. Examples of successful control operations can be cited in many Board areas. However, satisfactory control is seldom achieved throughout a Board's area. There are two basic reasons for this:

1.

Insufficient co-ordination of activities. Breakdowns in communication have, particularly in the past, resulted in failure or only poor success of control, e.g. when Boards have not given farmers sufficient notice to move stock, or when farmers have refused access to Board operators for various reasons, including trapping for skins, and their inability to de-stock some areas requiring control. For successful control it is essential that good co-operation exists between Boards and ratepayers. The Agricultural Pests Destruction Council has recognised this and is actively endeavouring to bridge the gap (e.g. see A.P.D.C. Annual Report 1977). It is essential that the communication be two-way, and that farmers, for example, advise the Board of any cropping and pasture development programmes.

2.

Lack of finance. Pest Destruction Boards are dependent on rates from farmers. However, the Boards are farmer-controlled, and in some cases appear reluctant to increase rate demands on fellow farmers, particularly when areas without a possum problem are included within the Board's jurisdiction. Few Boards strike differential rates. Most Boards are also reluctant to lower the level of rabbit control, which would make more money available for control of possums, for fear that rabbit populations might explode in the absence of continual control. In many cases, possums are causing more damage than rabbits, but the rabbits are still being hunted whereas the possums are not. There would appear to be a need for some form of differential rating or payment-for-service-rendered scheme.

These organisational and financial difficulties will need to be accounted for in any assessment of the cost-effectiveness of possum control.