Sunday, December 10, 2006 - 10:47 AM

Extrafloral nectaries on fava beans (Broad Windsor), Vicia faba L. and their attraction to nectar seeking insects

Mark E. Headings,, Ohio State University, Agricultural Technical Institute, 1328 Dover Road, Wooster, OH and Leslie A. Morris,, Ohio State University, USDA-ARS at OARDC, 1680 Madison Avenue, Wooster, OH.

Some plants produce extrafloral nectar in addition to floral nectar and both are attractive food sources for certain nectar seeking insects. The objective of field investigations conducted was to determine the presence or absence of extrafloral nectaries on 18 different types of beans and several other types of legumes. The authors previously reported finding extrafloral nectaries on mung beans, adzuki beans and cowpeas (California Blackeye No. 5). The focus of this report is on extrafloral nectaries which have also been found on fava beans (Broad Windsor), Vicia faba L.; however, they differ in structure and location compared to that of the other three. They are not located on plant stems as the previous three but rather on bract-like structures and appear as black spots. Close-up photographs of the structure of these extrafloral nectaries were produced using a Hitachi S-3500 variable pressure scanning electron microscope. It was observed that the multicolored Asian lady beetle, Harmonia axyridis and the small honey ant, Prenolepis impairis, were primary feeders at the extrafloral nectaries. Insects benefit from this food source; however, the benefit to the plant has not been determined.

Species 1: Coleoptera Coccinellidae Harmonia axyridis (multicolored Asian lady beetle)
Species 2: Hymenoptera Formicidae Prenolepis impairis (small honey ant)

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