| Understanding the mechanisms by which diversified habitats benefit natural enemies will improve biological control planning. Provision of flowering vegetation is expected to improve parasitoid fitness in the field. Lab and caged field studies demonstrate how sugar feeding enhances longevity and fecundity of parasitoids. Studies where parasitism rates are higher among fields diversified with flowering vegetation further support the importance of nectar sources. However, little is known about the proportion of parasitoids actually utilizing these sugar sources and how feeding impacts lifetime fecundity and foraging patterns in the field. This study tests the general assumption that parasitoid success is strongly impacted by the availability of sugar sources. More specifically, I tested whether: floral habitats improved local parasitism rates (Chapter 2), if parasitoids responded to the presence of nectar producing plants by feeding (Chapter 3), nectar and honeydew feeding increased longevity and fecundity of parasitoids in the field and lab (Chapter 4 and 5), and nectar sources enhanced host foraging behavior of parasitoids in the local area (Chapter 6). We tested the effectiveness of buckwheat, Fagopyrum esculentum Moench in cabbage fields over four years, 2000--2003. Three common pests, cabbage looper Trichoplusia ni (Hubner), imported cabbageworm Pieris rapae (L.) and diamondback moth Plutella xylostella (L.) and their parasitism rates were monitored in cabbage plots (12 x 20 m) with and without 3 m wide buckwheat borders. |
