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Developing integrated pest management tactics for alfalfa mosaic virus and its aphid vector in chile peppers


Alfalfa mosaic virus (AMV, Bromoviridae: Alfamovirus) is a virus transmitted to plants by aphids in a non-persistent manner. The virus was first identified in chile peppers Capsicum annuum L. (Solanales: Solanaceae) in Southern Colorado in 2019. The goal of this research was to explore management strategies to suppress the virus given its devastating impact on the yield and quality of chile peppers. The objectives were to: 1) determine whether chile peppers have innate resistance to AMV, 2) test the effectiveness of host plant resistance and planting date modifications to suppress the virus in the field, 3) determine whether AMV is seed transmissible, and 4) survey abundance and diversity of aphids (Hemiptera: Aphididae) that likely transmit AMV in the system. In the greenhouse experiment, I found significant differences among varieties of chile peppers in the severity of AMV symptoms and identified a variety suitable for a field experiment. In the field, I found that the susceptible variety, Joe Parker, which tended to have high AMV symptoms in the greenhouse, was also highly susceptible to AMV in the field. Conversely, Mira Sol, which appeared to have resistance to the virus in the greenhouse screening assay had low incidence of AMV symptoms and low AMV titers in the field as well. Planting date also played an important role in symptom severity, where late planted peppers (mid-June) had significantly lower severity of AMV symptoms than peppers planted at conventional and early planting dates (the middle and end of May). Despite this, the yield and quality of peppers planted early was significantly greater than that of peppers planted later in the season. In addition, there was evidence of seed transmission of AMV in chile peppers, with 10% for Mira Sol and 2% for Joe Parker, from seeds collected from infected peppers had AMV. Lastly, I found high diversity of aphid species within my experimental plots (14-16 species) and lower diversity in nearby alfalfa fields (4-5 species). Moreover, severity and titers of AMV were positively correlated with earlier planting date, which was likely related to higher aphid densities early in the season. This research contributed to formulating integrated tactics that chile pepper producers can implement in their production to suppress the impact of AMV on the crop. Finally, this is the first report of AMV transmission through seed in peppers and is the first study describing this pathosystems in Colorado.


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integrated pest management
plant pathology
chile pepper
alfalfa mosaic virus


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