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Thermal requirements and phenology of the Eucalyptus snout beetle Gonipterus scutellatus Gyllenhal
Author(s) -
SantolamazzaCarbone S.,
RodríguezIllamola A.,
Cordero Rivera A.
Publication year - 2006
Publication title -
journal of applied entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.795
H-Index - 60
eISSN - 1439-0418
pISSN - 0931-2048
DOI - 10.1111/j.1439-0418.2006.01073.x
Subject(s) - biology , curculionidae , parasitoid , phenology , snout , instar , pupa , pest analysis , larva , weevil , botany , ecology , zoology , horticulture
Laboratory experiments and field surveys were carried out to study the thermal requirements and phenology of the Eucalyptus snout beetle Gonipterus scutellatus (Curculionidae) and its parasitoid, Anaphes nitens (Mymaridae). Developmental times were recorded for G. scutellatus life stages: egg to first instar larva, first instar to pre‐pupal larva, prepupae to adults and the complete life cycle. Experiments were performed in temperature‐controlled chambers maintained at 10, 15, 20, 25 and 30°C with a photoperiod of 11 : 13 h of light : darkness and 50–60% RH. To calculate the minimum threshold temperature of the parasitoid, parasitized egg capsules were kept under similar conditions. During 1998 and 1999 we studied the phenology and the day‐degree (DD) accumulation of G. scutellatus and its parasitoid in plots of Eucalyptus globulus at six different sites in NW Spain. Every 2 weeks, the numbers of snout beetle adults and egg capsules were counted in each plot. The rate of parasitism was estimated by collecting 90 egg capsules from each plot on each sampling date. We recorded the temperatures in each plot to test whether differences in temperature alone could account for the phenology of this snout beetle. To complete a full life cycle from egg to adult, the weevil required a mean of 1119.83 ± 20.59 DD above a base temperature of 6.11°C. The parasitoid had a base temperature of 5.09°C and needed 318.16 DD to complete a life cycle. Our model indicated that three generations of snout beetle could develop each year, corresponding to peaks of snout beetle numbers in the field in March–April, June–July and November. In some years only one generation of G. scutellatus was recorded due probably to the effectiveness of the parasitoid. Differences in numbers of adults and egg capsule were recorded between neighbouring ‘coastal plots’ and between neighbouring ‘inland plots’. Hence, climate alone does not appear to explain the phenology of G. scutellatus .