The object of this paper is to discuss the ecology of grass
grub, Costelytra zealandica White, and porina, Wiseana
cervinata (Walker), New Zealand’s most important
pastoral insect pests, and to survey what has been achieved
in ecological understanding of these insects. The biology
and ecology of either or both insects have previously been
reviewed by Dumbleton (1942), Miller (1945), Kelsey
(1951a, b) and Hoy (1963). The lack of fundamental
biological information on grass grub (and this is equally
applicable to porina caterpillar) and the need for longterm
team studies were stressed, although little sustained,
co-ordinated research has since eventuated.
Examination of the literature clearly indicates that the
lack of fundamental ecological research on these pasture
pests is directly due to the introduction of organochlorine
insecticides, particularly DDT, to control both porina and
grass grub. These insecticides proved cheap, persistent
in soil, relatively safe to handle and easy to apply (Kelsey
and Hay., 1950; Kelsey 1951a, b, 1952, 1959). DDT was
so effective that it led to complacency, in spite of the
warning by Miller (1945) that in his view no single control
would suffice. There was failure to anticipate:
(1) Development of insect resistance. to insecticides.
(2) Possible alteration of tolerance limits for insecticides
in foodstuffs, by countries importing New Zealand
produce.
(3) Failure of DDT to be effective in certain soils.
(4) The need for fundamental knowledge, in case the
efficacy of DDT and related insecticides diminished,
and new methods had to be found.[Show full abstract]
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