New Zealand Journal of Agricultural Research abstracts
Intraspecific variation in the ability of Microctonus aethiopoides
(Hymenoptera: Braconidae) to parasitise Sitona lepidus (Coleoptera:
Curculionidae)
C. B. Phillips R. P. Cane
Biocontrol and Biosecurity Group
AgResearch
P.O. Box 60
Lincoln
Canterbury, New Zealand
J. Mee
H. M. Chapman
Plant and Microbial Sciences Department
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
K. A. Hoelmer
D. Coutinot
USDA-ARS European Biological Control
Laboratory
Campus International de Baillarguet
CS 90013 Montferrier-sur-Lez
34988 St. Gély du Fesc Cedex, France
Abstract Sitona discoideus (Coleoptera: Curculionidae),
a pest of lucerne (Medicago sativa), is controlled in New Zealand
by the introduced parasitoid Microctonus aethiopoides (Hymenoptera:
Braconidae). Unfortunately, a second Sitona species, S. lepidus
(=flavescens), which has recently invaded New Zealand and has become a pest
of white clover (Trifolium repens), is not parasitised by M. aethiopoides.
Previous experiments have shown that New Zealand M. aethiopoides will
attack S. lepidus, but its eggs appear to be killed by the host immune
response. In contrast, M. aethiopoides has been observed to successfully
parasitise S. lepidus in Europe. It is possible either that New Zealand
S. lepidus has a more effective immune response to M. aethiopoides
than European S. lepidus, or that New Zealand M. aethiopoides
is less able to evade the S. lepidus immune system than European M.
aethiopoides. An experiment was conducted to compare the suitability
of French and New Zealand S. lepidus as hosts for French M. aethiopoides.
This provided no evidence of S. lepidus intraspecific variation in
host suitability for parasitism. Furthermore, amplification of inter simple
sequence repeat (ISSR) regions of M. aethiopoides DNA demonstrated
clear genetic differences between French and New Zealand M. aethiopoides.
It was concluded that intraspecific variation in the ability of M. aethiopoides
to evade the immune response of S. lepidus is the reason for the low
levels of parasitism observed in New Zealand compared with Europe. Development
rate data for M. aethiopoides larvae and pupae are reported.
Keywords biological control; host range; host suitability;
inter simple sequence repeat; intraspecific variation; development rate;
Microctonus aethiopoides; Sitona discoideus; Sitona flavescens;
Sitona lepidus
A02010 Received 14 February 2002; accepted 19 August 2002; published 9
December 2002
New Zealand Journal of Agricultural Research, 2002, Vol. 45: 295-303
0028-8233/02/4504-0295 $7.00/0 © The Royal Society of New Zealand
2002
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