This study focuses on the effective biocontrol agent Chilocorus
nigritus (Fabricius). Its behaviour and ecology were compared
with other Chilocorus spp. where appropriate, to elucidate why
this species is such an effective biocontrol agent, and how to
improve methodology for its deployment as a natural enemy. An
artificial diet for C. nigritus was developed, but was still
sub-optimal. Asterolecanium miliaris (Boisduval) was a
suitable prey for all life stages of C. nigritus and the adults
of Chilocorus bipustulatus (Linnaeus) and Chilocorus infernalis
Mulsant, but was inadequate for larvae of the last two species.
Adult weight, measured at one day after adult eclosion, was an
appropriate indicator of the effects of larval treatment on
their development and on the fitness of subsequent adults.
There was no improvement in culture vigour due to a behavioural
response of individuals within one generation to fluctuating
as opposed to constant temperature. starvation for between 10h
and 24h was appropriate for standardisation of hunger.
Measuring feeding rate at a range of static temperatures did
not reflect differences in the climatic adaptations of six
Chilocorus spp., but mortality rates at increasingly high
temperatures were useful. Chilocorus spp. showed little
ability to choose between prey species. Prey substitutions
adversely affected adults and larvae. Introduction of adults
was the most effective method for field establishment. Giant
bamboo Dendrocalamus giganteus Munro was a valuable site for
field releases of C. nigritus, but less useful for C. bipustulatus and C. infernalis. Counter to assumptions on
which interference models have been based, no significant
intraspecific interference, reducing predatory efficiency, was
observed. Visually prominent features on the horizon and a
specific leaf shape, were attractive to foraging C. nigritus.
The location of prey patches by adults was facilitated by prey
odour, but not so for larvae. Adults detected individual prey
olfactorily and visually over short distances, but physical
contact was required for detection by larvae. Prey location
by larvae and adults was facilitated by alterations in movement
patterns in response to prey consumption. Differences in prey
detection and the effects of prey substitutions, between the
life stages, were related to field behaviour. The relevance
to biological control, of responses to rearing conditions and
feeding and foraging behaviour, was investigated. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1991.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10958 |
| Date | 20 June 2014 |
| Creators | Hattingh, Vaughan. |
| Contributors | Samways, Michael J. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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