Evaluation of Floral Habitat as a Food Source for Natural Enemies of Insect Pests in North Carolina

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Title: Evaluation of Floral Habitat as a Food Source for Natural Enemies of Insect Pests in North Carolina
Author: Witting, Brooke Ellen
Advisors: John M. Dole, Committee Member
H. Michael Linker, Committee Co-Chair
David B. Orr, Committee Co-Chair
Abstract: A field study was conducted in 2004 and 2005 to observe flower-feeding of potential beneficial insectary plants by insects. Sixteen flower species were individually observed once weekly for two minutes beginning between 12 and 1 pm in 2004. Five species were observed twice weekly beginning at 9:30 am and 12 pm in 2005. Insects were identified to family level and analyzed by feeding guild. In both years, predators were observed feeding from fennel (Foeniculum vulgare P. Mill.) flowers in greater abundance than from any other flowers observed. Fennel also was fed upon most often by parasitoids in 2005. Pollinators were observed feeding most often from Indian blanket (Gaillardia pulchella Foug.) in 2004 and from black-eyed Susan (Rudbeckia hirta L.) and buckwheat (Fagopyrum esculentum Moench) in 2005. In both years, herbivorous crop pests, deleterious and non-crop parasitoids, and deleterious predators were not significantly affected by flower species. A field study was conducted in August 2005 to determine the relative attractiveness of floral habitat to three families of microhymenopteran egg parasitoids: Mymaridae, Scelionidae, and Trichogrammatidae. Habitat plants were yarrow (Achillea millefolium L.), celosia (Celosia cristata L.), buckwheat, fennel, daisy (Leucanthemum x superbum (J. W. Ingram) Berg. ex Kent.), and black-eyed Susan. Non-flowering crabgrass (Digitaria sp. Haller) served as a control. Sticky traps were used to monitor microhymenoptera and were placed at three heights: flower height, 0.5 times flower height, and 1.5 times flower height. Flower heads were removed from half of each plot and traps were placed in the center of each subplot. Results from this experiment show that flower species and height affected all three families of microhymenoptera but flower removal only affected scelionids. At flower height, scelionids were trapped in greater abundance in celosia plots at flower height in flowers-present versus flowers-removed treatments. Trichogrammatids were trapped in greatest abundance at 0.5 times flower height in un-mowed crabgrass plots and mymarids were most abundant at 0.5 times flower height in black–eyed Susan plots. Our results indicate that habitat plantings may attract microhymenoptera but that flowers themselves do not appear to be responsible for this attraction. A combined laboratory and field study was conducted to determine the effect of different food sources on the longevity and fecundity of Trichogramma exiguum Pinto & Platner and the longevity of Cotesia congregata (Say). Newly eclosed (<12 h) female wasps were provisioned with one of two treatments: fennel or buckwheat flowers, or one of two controls: honey or water. Wasps were monitored daily until all had died. Fecundity of T. exiguum was monitored using Ephestia kuehniella Keller egg cards. Longevity was greatest in T. exiguum provisioned with honey and in C. congregata provisioned with buckwheat flowers. Buckwheat provisioned T. exiguum exhibited greater longevity than those provided fennel. Longevity of C. congregata provisioned with fennel and honey was approximately equal. Water provisioned T. exiguum and C. congregata exhibited the shortest longevity. Total fecundity was greatest in T. exiguum provisioned with honey or buckwheat. Average female to male ratio over the lifetime of each female was greatest in T. exiguum provisioned with water alone, likely because of sperm limitation in wasps exhibiting greater longevity. Total average number of female offspring produced was greatest in T. exiguum provided honey or buckwheat flowers although no difference in total female offspring were observed between adults provisioned with buckwheat or fennel flowers. Our results show that provisioning T. exiguum with honey and buckwheat flowers caused greater longevity, total fecundity, and lifetime production of female offspring than water alone. Buckwheat flowers also lead to greater longevity in C. congregata.
Date: 2006-05-04
Degree: MS
Discipline: Entomology
URI: http://www.lib.ncsu.edu/resolver/1840.16/817


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