The potato leafhopper (PLH) and Colorado Potato Beetle (CPB) co-occur as major pests in potato fields throughout the United States. The potato leafhopper, a sap-feeding insect, feeds early in the season on potatoes and results in damage such as leaf curling and yellowing to foliage. Colorado Potato Beetle, a mandibulate herbivore colonizes fields later in the season and feeds on the same plant tissues previously fed upon by Potato Leafhopper. We examined the possibility that previous feeding by leafhoppers induces changes in potato physiology that result in resistance to Colorado Potato Beetle. By introducing leafhoppers at several densities (low, medium and high) into field-caged potato plants early in the season and allowing them to feed, we were able to examine the effects that PLH feeding had on the subsequent performance of CPB. Our results indicate that previous feeding by the PLH induces a physiological response in potatoes that has adverse consequences on the development time and survivorship of CPB. This study provides evidence for an asymmetric competitive interaction between two herbivores in very different feeding guilds. The results add to the growing number of cases demonstrating the importance of lateral effects in communities of phytophagous insects. Further, our results bear on adjusting the economic threshold for PLH to reflect the adverse effects it has on CPB.
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