Graduate Thesis Or Dissertation
 

A survey of alfalfa pollinators and polination in the San Joaquin Valley of California with emphasis on establishment of the alkali bee

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  • The study involves the establishment, management, and behavioral observations of Nomia melanderi Cockerell and Megachile rotundata (Fabricius) in California, a survey of native bees within western Fresno County, a determination of selfing and/or parthenocarpy in two fields of alfalfa, and observations on the honeybee as an alfalfa pollinator. The alkali bee is characterized. It is an endemic species limited to western North America. Eight artificial alkali bee nesting sites were constructed during the establishment program. Details of materials used during construction and their importance are discussed. Alkali bee cores used for introduction into California were procured in eastern Oregon and western Idaho, trucked to California, and planted in artificial sites. The heavy usage of insecticides in the area of study proved to be the greatest problem in the survival of the alkali bee. Observed toxicities of Dimethoate, Sevin, Malathion, Systex-Toxaphene, Toxaphene, DDT, Phosdrin, Dibrom, TEPP, Dylox, and Kelthane on the alkali bee were compared. The occurrence of multiple generations of the alkali bee in California is reported. Explanation of this behavior is based upon high soil temperatures (82° F. and above) during the nesting season. The importance of multiple generations is discussed. Biologies and importance of alkali bee parasites in California are described. Procedures for the control of some species are outlined. Methods of constructing trap nests for Megachile rotundata and their distribution throughout the San Joaquin Valley are described. Collections of these trap nests were then made and placed in one field so that readings on frequency of tripping, number of pollen loads required to provision cells, and time required to collect leafcuttings could be made. Observations on mating positions were described. The smallest males and largest females were reproductively isolated because of size difference. Parasites (Melittobia chalybii Ashmead and Monodontomeris montivagus Ashmead) and competitors (Ashmediella aridula Cockerell and Hylaeus grossicornis (Swenk and Cockerell) of Megachile rotundata are discussed. Melittobia chalybii Ashmead, a chalcid wasp, is potentially the most serious parasite and could decide the success or failure of M. rotundata in California. A survey of native bees was made in the area of study. Eight native species were found and their biologies described. Preferred pollen host plants were determined. Reasons why native bee biologies should be studied and understood are given. Two cages, one placed in a Tan Verde seed field and the second in a Ranger field, were used to calculate amount of seed produced from pathways other than by cross-pollination. Comparison of seed harvested from caged plots and field plots indicated that seed produced by non cross-pollination mechanisms could account for the average seed yields in California during recent years. Germination tests indicated, however, that seed produced by mechanisms other than cross-pollination is inferior. Only seven honey bees were observed collecting alfalfa pollen throughout the period of study. Consequently, no valid comparison between its pollinating capacity and that of wild bees could be made.
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