Climate change research has primarily focused on the consequences of increasing average global temperature. However, extreme weather events are another consequence of climate change that has been harder to examine because of their rarity and unpredictability. Heat waves are brief events of extreme heat that pose an immediate threat to food security and agricultural sustainability and are predicted to increase exponentially in frequency over the next fifty years. The effect of heat stress on single organisms are well known, but we have a poor understanding of how the timing of heat wave events influence plant-insect-disease interactions in agroecosystems. In this thesis, I address two primary research questions: 1) How does timing of a heat wave impact crop-pest interactions? 2) How are multi-species interactions influenced by heat waves? I used environmental chambers in the lab and open-top chambers fitted with infrared heaters in the field to simulate heat wave conditions at early and late development stages of potato (Solanum tuberosum) inoculated with an associated herbivore the Colorado potato beetle (CPB, Leptinotarsa decemlineata, (Say) (Coleoptera: Chrysomelidae)) and foliar disease early blight caused by (Alternaria solani). I found that heat waves increased CPB larval mass by 26-44% and sped up development time, suggesting there could be an additional generation of herbivores per season. Heat waves combined with herbivore and disease stress caused 20-40% lower yield on potatoes in early reproductive stages. Actions should be taken to protect crops in early reproductive stages from stress through diligent irrigation practices and more frequent scouting to inform pest management strategies prior to and during heat waves.
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