Some effects of grass grub(Costelytra zealandica (White))larvae on pasture plants

Abstract

ABSTRACT

Effects of grass grub (Costelytra zealandicawhite) larvae on pasture plants

“…These results in simulated swards agree with earlier work with spaced plants (Radcliffe 1970) that showed white clover in monoculture to be more susceptible to grub damage than white clover in mixture with perennial ryegrass. However, there was no evidence that white clover was preferentially damaged in mixture with ryegrass, and this is in contrast to the earlier experiment (Radcliffe 1970) in which counts of visually damaged plants clearly showed white clover to be more susceptible.…”

“…However, there was no evidence that white clover was preferentially damaged in mixture with ryegrass, and this is in contrast to the earlier experiment (Radcliffe 1970) in which counts of visually damaged plants clearly showed white clover to be more susceptible. These different findings may be partly due to the growth stage of white clover; in the earlier experiment clover remained at a younger growth stage with poorly developed stolons, but in the present experiment clover growth was more advanced.…”

“…Grubs were not observed feeding on shoots on the soil surface, although this had been observed in earlier work with similar soil media (Radcliffe 1970). The apparent absence of surface-feeding grubs may have been due to higher plant populations obscuring grubs on the surface and / or providing more root material and a more attractive soil medium.…”

“…They were grown in autumn and winter, a period of active initiation and growth for roots of perennial ryegrass (Jacques and Schwass 1956), and probably also for cocksfoot. Although root growth was probably stimulated by dung in the soil medium (Radcliffe 1970;Davidson and Roberts 1968), it may also have been slightly suppressed by the reduction in incident sunlight within the screen house.…”

“…Seed was sown at uniform spacings on 14 April in tins 23 em X 23 em X 20 em deep filled to a depth of 18 em with moist, moderately compacted, fine to medium pumice sand described by Radcliffe (1970). Plants were later thinned to give 64 uniform seedlings per tin (114 plants per 30 ems).…”