| dc.description | The pathogenicity of native fungal isolates, Beauveria bassiana, Metarhizium anisopliae, and Verticillium lecanii , and a commercial formulation of B. bassiana, BotaniGard (GHA strain) against adult Lygus lineolaris Palisot de Beauvois (Hemiptera, Miridae) was investigated with particular emphasis on the influence of body region and topography on spatial conidial deposition patterns and germination of conidia as they related to the fate of the insect. Mycosis was induced by all isolates tested, and not surprisingly, BotaniGard was the most virulent. Electron microscopic assessment of the cuticle revealed that conidia were capable of attachment and subsequent germination for all isolates tested. Relatively few conidia were observed having attached compared to the total number sprayed on the insect. Furthermore, the number of germinating conidia was a small proportion of those that adhered, suggesting that germination may be a limitation for infection. Significant differences were detected between infected versus uninfected insects based on germinating conidial counts in relation to body region and both conidial and germinating conidial counts for surface topography. Appressorial development in germinating conidia was also affected by surface topography. Despite the fact that the native fungal isolates used in laboratory assays had been collected in Nova Scotia, a 2-year survey of L. lineolaris populations in apple orchards and fields, did not detect incidence of natural fungal infection. Although, the direct spraying of BotaniGard and M. anisopliae in laboratory trials resulted in high mortality, field applications will not likely realize the same level of success. Successful biological control using fungal pathogens against L. lineolaris requires contact between the insect host and the pathogen. Since both body region and surface topography of the insect cuticle influenced the spatial deposition patterns of conidia and germination, promoting conditions that favour disease development at the conidia-cuticle interface may play a more critical role in the future use of fungal pathogens against L. lineolaris. This finding emphasizes the need for novel application strategies that will increase the likelihood that conidia will be delivered in a sufficient dose, to the right location on the insect cuticle, while under conditions that will favour early development of the pathogen. | en_US |
