Among several early-season insect pests threatening apple production in eastern North America, plum curculio (PC), Conotrachelus nenuphar Herbst (Coleoptera: Curculionidae), is one of the most devastating pests of pome and stone fruits. Historically, several methods have been used to monitor and control plum curculio in apple orchards. The odor-baited trap tree approach has proven to serve as an effective monitoring and attract-and-kill system for plum curculio. The synergistic lure consisting of benzaldehyde (a plant volatile) and grandisoic acid (the PC aggregation pheromone) is used in this approach. However, the high cost of the lure and the degradation of benzaldehyde by UV light and heat have resulted in limited grower adoption. The major goals of this study were (1) to evaluate under field conditions, the attractiveness of methyl salicylate (MES) to PC, and to determine if it can replace the benzaldehyde (BEN), and (2) to test whether we can manipulate insect pest behavior through host plant preference by grafting selected perimeter- row trees with multiple cultivars. My results indicated that (1) methyl salicylate in combination with grandisoic acid was as attractive to PC as the standard synergistic lure composed of benzaldehyde and grandisoic acid, therefore MES can be used as a replacement for BEN, (2) trees grafted with six cultivars were more attractive to PC and concentrated more PC fruit injuries, compared to non-grafted trees, and (3) ‘Wickson’ and ‘Red Astrachan’ received numerically more PC injuries while ‘Dabinett’ received the lowest level of injury compared with other cultivars. These results highlight that a semiochemical-based strategy is a low-cost and grower-friendly approach to monitoring and controlling the PC population.

Plum curculio, Conotrachelus nenuphar (Herbst), is an endemic pest of stone and pome crops of the eastern United States. Two morphologically identical strains of plum curculio have been described and documented in Virgina: a univoltine strain and a multivoltine strain. Because of the cryptic coloring and behaviours of the plum curculio adults, monitoring in orchards is difficult and often ineffective. RAPD-PCR assay was an effective method for separation of the geographical strains. Of the tested primers four, OPE 01, OPE 03, OPE 04, and OPE 07, gave 21 amplimers that are useful for distinguishing individuals from the univoltine and multivoltine populations. Gene targeted PCR revealed the presence of Wolbachia in both populations. Analysis of the wsp gene sequence showed the univoltine population of plum curculio is associated with a strain of Wolbachia in supergroup B, most closely related to a strain identified from Perithemis tenera (Say) (Odonata). The multivoltine populations of plum curculio are associated with strains of Wolbachia which are in supergroup A, and most closely related to Wolbachia strains associated with Dacus destillatoria, Bactrocera sp., and Callosobruchus chinensis Linn. Three different trap designs baited with grandisoic acid, plant volatiles, and a combination of pheromone and plant volatiles were tested. In 1999, significantly more plum curculios were captured with Tedders traps baited with grandisoic acid and unbaited control in traps baited with limonene, plum essence or ethyl isovalerate. In 2000, Circle traps baited with plum essence, sour cherry essence and grandisoic acid yielded no results. In 2001, branch mimic traps yielded no significant differences among three release rates of a blend of benzaldehyde, ethyl isovalerate, trans-2-hexenal, and limonene; although, there was a significant interaction between the pheromone and the host plant volatiles. Overall however, all three of the traps were not effective. / Master of Science

Les théories relatives à la biodiversité contrastent fortement quant au rôle qu’elles accordent aux différences de traits écologiques entre espèces (théorie des niches) ou à la stochasticité démographique (théorie neutre de la biodiversité) pour expliquer l’organisation des communautés d’espèces compétitrices. Les espèces en compétition pour une ressource pulsée permettent de tester à relativement court terme ces théories : dans le cadre de la théorie des niches, les espèces en compétition devraient présenter de fortes différences de traits les conduisant à exploiter différemment la ressource pulsée; elles devraient alors répondre démographiquement de manière différente aux fortes fluctuations en ressources et leurs dynamiques populationnelles devraient être asynchrones. Au contraire, dans le cadre de la théorie neutre, les espèces ne devraient pas présenter de différences majeures dans leurs caractères associés à l’exploitation de la ressource variable; elles devraient alors répondre de la même manière aux pulses et leurs dynamiques populationnelles devraient être synchronisées. Nos travaux, centrés sur quatre espèces du genre Curculio en compétition pour l’exploitation des glands de chêne, permettent de mettre en évidence (i) qu’un fort partitionnement global de leurs niches est assorti de dynamiques populationnelles asynchrones. (ii) Cependant, ils montrent également que deux des quatre espèces compétitrices apparaissent très similaires quant aux caractères étudiés et présentent des dynamiques de population synchronisées. Les résultats, dans leur ensemble, fournissent donc l’un des premiers arguments empiriques en faveur d'une théorie unifiée de la biodiversité / Understanding the organization of communities composed of competing species, and notably their biodiversity, has led to two theories that sharply contrast with each other about the role primarily assigned either to the differences in ecological traits among the species (niche theory) or to the demographic stochasticity (neutral theory of biodiversity). Species competing for a pulsed resource allow testing the two theories in short-term studies: the niche theory predicts that differences should exist in the traits of such species, which should allow them taking advantage of the resource in various ways; the species should thus respond differently to the fluctuations in the availability of the resource, resulting in asynchronous population dynamics. In contrast, the neutral theory predicts that the trait differences possibly existing between the species should not impact the way they use the variable resource; the species should then respond similarly to the pulses and their population dynamics should be synchronized. Our work, focusing on four phytophagous insect species (Curculio spp.) that compete for oak acorns (Quercus spp.), (i) show evidence of a clear, global niche partitioning combined with asynchronous population dynamics (ii) but points out that two of these species show similar ecological traits and display synchronized population dynamics. Overall, these results therefore provide one of the first empirical arguments in favor of a unified theory of biodiversity

abstract: Weevils are among the most diverse and evolutionarily successful animal lineages on Earth. Their success is driven in part by a structure called the rostrum, which gives weevil heads a characteristic "snout-like" appearance. Nut weevils in the genus Curculio use the rostrum to drill holes into developing fruits and nuts, wherein they deposit their eggs. During oviposition this exceedingly slender structure is bent into a straightened configuration - in some species up to 90° - but does not suffer any damage during this process. The performance of the snout is explained in terms of cuticle biomechanics and rostral curvature, as presented in a series of four interconnected studies. First, a micromechanical constitutive model of the cuticle is defined to predict and reconstruct the mechanical behavior of each region in the exoskeleton. Second, the effect of increased endocuticle thickness on the stiffness and fracture strength of the rostrum is assessed using force-controlled tensile testing. In the third chapter, these studies are integrated into finite element models of the snout, demonstrating that the Curculio rostrum is only able to withstand repeated, extreme bending because of modifications to the composite structure of the cuticle in the rostral apex. Finally, interspecific differences in the differential geometry of the snout are characterized to elucidate the role of biomechanical constraint in the evolution of rostral morphology for both males and females. Together these studies highlight the significance of cuticle biomechanics - heretofore unconsidered by others - as a source of constraint on the evolution of the rostrum and the mechanobiology of the genus Curculio. / Dissertation/Thesis / Doctoral Dissertation Evolutionary Biology 2009