Abstract
Coraebus florentinus (Herbst) is one of the most important wood borer pests of oaks in forest ecosystems in the Mediterranean Region. It is considered to be a heliophilous species as it prefers the sunniest parts of the canopy of isolated trees. The biological significance of this preference is still unknown. Recently, the effect of temperature on the preimaginal development of this insect was established: high temperatures increase its probability of survival and shorten its developmental time. Continuing this line of research, this study was designed to determine whether C. florentinus exhibits selective oviposition behaviour and how variation in temperature due to differences in the position of the branches in which the larvae develop could affect the subsequent development of this species. To determine whether this insect selects the branches in which to lay its eggs, location data (north, south, upper half and lower half of the tops of the trees) for 112 damaged branches were analysed. The results confirm that females of C. florentinus do not lay their eggs at random at the tops of trees but rather choose branches that are exposed to the sun. To determine the effects of larval rearing temperature on the later development stages, an experiment consisting of five treatments was performed. Four of these treatments, each containing 25 infested branches derived from different orientations and positions in a tree (upper half of tree and north facing, upper half and south facing, lower half and north facing and lower half and south facing) were kept in culture chambers maintained at optimal conditions for pupal development (28 ± 2°C and 60-65% relative humidity). The fifth treatment with 25 branches infested collected from the most sun-exposed locations were kept in outdoor conditions. The results indicate that variation in temperature during larval development due to differences in branch location does not significantly affect survival, duration of developmental of pupae, emergence success or sex ratio of the adults.
Highlights
Coraebus florentinus (Herbst, 1801) is a xylophagous beetle of the Buprestidae Family, which attacks and damages mainly different species of Quercus (Schaefer, 1949; Zochi, 1953; Goidanich, 1954; Soria, 1990; Cárdenas & Gallardo, 2012)
The 112 branches observed in the field showing clear symptoms of damage by C. florentinus were pooled according to their position and orientation in the tops of the trees (Table 1)
The results indicate that neither the location of the branches in the canopy nor the conditions in which the branches were kept influenced the time for which the adults of C. florentinus survived (F = 1.76, P = 0.15)
Summary
Coraebus florentinus (Herbst, 1801) is a xylophagous beetle of the Buprestidae Family, which attacks and damages mainly different species of Quercus (Schaefer, 1949; Zochi, 1953; Goidanich, 1954; Soria, 1990; Cárdenas & Gallardo, 2012). Damage caused by C. florentinus is due to the feeding activity of larvae, which bore longitudinal and annular galleries under the bark of terminal branches that interrupt the sap flow and cause the death of branches in which this insect completes its development This reduction in the number of branches results in a progressive decay and loss of vigour (Jurc et al, 2009). The symptoms of the damage are identifiable and are widely described in the literature (Bachiller et al, 1981; Montoya, 1988; Soria & Ocete, 1993; Cárdenas & Gallardo, 2012) The abundance of this insect is greatest in several countries in the Mediterranean basin (Italy, Spain and Portugal; Jurc et al, 2009), where the level of damage has considerably increased recently. This is because of the progressive abandonment of pruning before the emergence of the imago (Lombardero & Fernández de Ana Magán, 1996), this is considered the most effective method of control (Evans et al, 2004)
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