Abstract
(Englisch)
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Life table studies have been developed by CABI Bioscience Switzerland to assess the significance of natural mortality factors acting on Diabrotica populations in its area of introduction in southeastern Europe (Hungary). Life tables will provide an understanding of the role and function of natural enemies as mortality factors on life stages of Diabrotica, and provide information on mortality factors, which might potentially influence the population dynamics of this maize quarantine pest. Findings will provide information about host niches of Diabrotrica that are presently not attacked by native natural enemies. Information will be used to identify potential natural enemies studied in the area of origin. Exotic parasitoid species will be further tested by CABI in a quarantine laboratory at Delemont with the intention of selecting candidate biological control agents for potential importation and establishment into Europe. Prior to the importation of exotic biological control agents the host specificity of the agent has to be identified that will allow to predict their field host range and to evaluate potential non-target risks.The first step in the evaluation of the potential of classical biological control is the assessment of the native natural enemy community of Diabrotica present in the invaded area in Europe. It can be concluded after a two year survey study, that all developmental stages of D. virgifera are not attacked by effective natural enemies in southeastern Europe. Except the fungi species Beauveria bassiana and Metarhizium anisopliae attacking Diabrotica adults on a low level, no other entomopathogenic fungi, entomopathogenic nematodes, and parasitoids were found, neither on eggs, nor on larvae, pupae or adults. From life table studies it can be concluded that the total generational mortality (K) of the Diabrotica population studied in southeastern Hungary was highest during the overwintering period of the egg stage with 24% and in the first instar larval stage with 67%. In total, death by Diabrotica by these two factors accounting for 91% of the total generational mortality in 2001. The extremely low mortality in the second and third instar larval stage and in the adult stage is indicating that host niches are not occupied by effective native natural enemies. The tachnid fly Celatoria compressa has been obtained from Mexico in collaboration with Dr Astrid Eben. In addition, the braconid Centistes gasseni and the tachinid fly Celatoria bosqui have been obtain from Argentina in collaboration with Dr Guillermo Cabrera Walsh. The selection of potential non-target host species based on literature reviews, museum records, expertise from taxonomists, and by using simplifying considerations has lead towards the establishment of a species list for host specificity testing of Celatoria species under quarantine laboratory conditions. At the end of 2001, important steps were made forward in establishing a rearing of the candidate biological control agent Celatoria followed by studies about its mating and oviposition, biology, larval morphology, impact efficiency, and its host specificity under quarantine laboratory conditions.
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