Date of Award

Fall 12-15-2017

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Advisor

Andrei Alyokhin

Second Committee Member

Seanna Annis

Third Committee Member

Frank Drummond

Additional Committee Members

Jim Dwyer

Abstract

Colorado potato beetle (Leptinotarsa decemlineata) (CPB) and Potato Virus Y (PVY) are two of the most damaging pests attacking potato crops. CPB can cause significant defoliation to potato fields and is difficult to control using insecticides because its populations rapidly develop insecticide resistance. PVY, which is transmitted non-persistently by aphids, can result in yield loss and rejection of seed potato lots. Due to its rapid mode of transmission, insecticides are often ineffective at curtailing the spread of the virus. Thus, an integrated pest management (IPM) approach is essential for both CPB and PVY control.

Mineral oil is a product used to reduce PVY transmission in potato fields. However, there is little information available about other effects that oil may have on insect pests of potato. To better understand how mineral oil affects potato pests, we performed a series of experiments testing the effects of oil on mortality, behavior, and development of aphids and Colorado potato beetles. Oil was harmful to aphids, acting as a contact insecticide, causing high levels of residual mortality to nymphs, and inducing avoidance of oil-treated foliage. Colorado potato beetles were also negatively affected by oil. Additionally, oil acted synergistically with the entomopathogenic fungus Beauveria bassiana; CPB larvae were killed more rapidly when sprayed with both products compared to when sprayed with B. bassiana alone. Based on these results, mineral oil has potential for expanded use in potato IPM programs.

The epidemiology of PVY is complex and poorly understood. We constructed a spatially-explicit, agent-based simulation model to improve understanding of the factors affecting PVY spread. According to the results of the model, initial inoculum and vector transmission efficiency are both important. The model also showed that aphids that do not colonize potato spread PVY more effectively than potato-colonizing aphids. Field size did not affect PVY spread. The results emphasize the importance of both planting clean seed to keep virus levels low as well as treating fields with mineral oil to effectively reduce transmission efficiency of aphid vectors. In addition, control should focus on reducing spread by non-colonizing aphids rather than on attempting to eliminate colonizing aphid populations.

Included in

Entomology Commons

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