Western Corn Rootworm 1 Adult and Spotted Cucumber Beetle 1 Associations with Cucurbita and Cucurbitacins

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Abstract
The western corn rootworm (WCR), Diabrotica virgifera LeConte, demonstrated strong affinities for aggregation and feeding on the foliage of certain wild Cucurbita species with relatively high concentrations of cucurbitacin “bitter principles.” Most preferred were xerophytic species of the Digitata group— C. digitata Gray, C. cylindrata Bailey and C. palmata Wats. and mesophytic species of the Lundelliana group— C. lundelliana Bailey, C. okeechobeensis Bailey and C. ecuadorensis Cutler and Whitaker. Xerophytic species were more susceptible to injury and seldom survived continuous 24-h exposure to natural infestations. The spotted cucumber beetle (SCB), D. undecimpunctata howardi Barber, exhibited similar aggregation and feeding responses to wild mesophytic Cucurbita species with high cucurbitacin foliage but showed a more consistent feeding preference for cultivated species than the WCR. Both species preferred fruits of feral C. texana Gray and C. andreana Naud. with high cucurbitacin over non-bitter fruits of their cultivated relatives, C. pepo L. and C. maxima Duchesne, respectively. The combined plant and insect factors which interact to bring about the SCB-WCR/ Cucurbita associations observed here are discussed.