Spatial distribution and movements of plum curculio adults within caged apple trees
1994
Chouinard, Gérald | Hill, Stuart B. | Vincent, Charles
In the spring of 1987 and 1988, ⁶⁵Zn labeled plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), were released within two field cages, each containing four dwarf apple trees. The cages were surveyed regularly between ‘pink' and 22 d after ‘fruit set' stages, and the location of labeled insects and substrates occupied were recorded. Labeled beetles first appeared in trees between ‘pink' stage and beginning of bloom, and the number within trees gradually increased until ‘petal fall' stage. Between ‘full bloom' and 22 d after ‘fruit set' stages, adults were found on the ground in 54% of the observations. At ‘petal fall' stage, the main host structures occupied were spurs, twigs, and flowers or fruit. Height in the trees, rate of movement (cm/h), and occurrence on the ground, spurs, flowers or fruits, and leaves and new annual growth, were related to the product of air temperature and relative humidity. Most dispersal from tree to tree occurred between ‘full bloom' and ‘fruit set' stages. Highest occurrence in trees was observed between 1800 and 0000 h. In the daytime, labeled adults tended to leave host structures except spurs, which were used as resting sites, mostly by females. Females occurred significantly higher in the tree canopy than males, although egg-laying was most frequent at mid-level. During bloom, up to 30% of plum curculios were found to rest simultaneously at the base of tree trunks, prior to their gradual invasion of trees. This behavior should be taken into account in the development of an effective shelter trap for monitoring this insect, and in the design of integrated control strategies.
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