New Zealand Journal of Zoology abstracts
The effect of temperature on the development and survival of
Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae),
a biological control agent for alligator weed (Alternanthera
philoxeroides)
C. A. STEWART*
R. B. CHAPMAN
R. M. EMBERSON
Department of Entomology and Animal Ecology
P.O. Box 84
Lincoln University
Canterbury, New Zealand
P. SYRETT
Landcare Research
P.O. Box 69
Lincoln, New Zealand
C. M. A. FRAMPTON
Centre for Computing and Biometrics
P.O. Box 84
Lincoln University
Canterbury, New Zealand
*Current address: Ministry of Agriculture and
Forestry, P. O. Box
2095, Auckland 1015
Abstract Agasicles hygrophila was introduced into New
Zealand in 1982 for the biological control of alligator weed, Alternanthera
philoxeroides. The optimum temperature for A. hygrophila
development was 27-30deg.C where development time was 19-20 days. Mortality was
lowest (13-14%) at temperatures between 23-25deg.C. The estimated lower
development threshold for A. hygrophila was 13.3deg.C. Adult
beetles reared at 23-27deg.C were heavier than those reared at 15-20deg.C and
30deg.C, and females were heavier than males. There was significant mortality
of adults during exposure to low temperatures. Mortality was 92% for adults
exposed for four weeks at 10deg.C and 70% for adults exposed for 12 weeks at
15deg.C. The number of eggs laid subsequently decreased as the time adults were
exposed to chilling was increased. Viability decreased as the temperature to
which adults were exposed was lowered, and with increased chilling time.
Females survived longer than males when chilled at 10deg. and 15deg.C. All
adults died when chilled for 13 h at -8deg.C; at 2deg. and -4deg.C there
was high adult survival, but the viability of eggs laid was low. These results
suggest the over-wintering capacity of A. hygrophila is much
reduced when exposed to temperatures of 15deg.C and below.
Keywords Agasicles hygrophila; Alternanthera
philoxeroides; alligator weed; temperature development; lower temperature
development threshold; low temperature survival; biological control
Z98010
Received 10 March 1998; accepted 3 August 1998
PDF file of entire paper: medium quality (799K); (scanned from paper original: notes about this process)
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