Biochemical Separation of Geographical Strains of Plum Curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), and Evaluation of Olfactory Attractants in Virginia Orchards
McClanan, Michelle Erin Garlic
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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.
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