Theses and Dissertations - UTB/UTPA
Development of mass-rearing techniques for Aphelinus asychis Walker for use in a biological control program against Russian wheat aphid
Date of Award
Master of Science (MS)
Dr. Mohammed Farooqui
Dr. Robert I. Lonard
Dr. Sammie L. Sides
Mass-rearing techniques were developed for the parasitoid Aphelinus asychis Walker (Hymenoptera:Aphelinidae) for use in a biological control program against the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera:Aphididae). Daily ovipositional activity, host-feeding behavior, effects of population density in the rearing cages and effects of cold storage on mummies were determined.
Daily ovipositional activity peaked at day 5 after emergence of the parasitoid. Ninety-two percent of mummies resulting from ovipositional activity were oviposited the first 13 days of the parasitoid’s life. Since mummification occurred 11 days after oviposition and emergence occurred 11 days after mummification, day 24 was determined to be the optimum day to harvest mummies for biological control shipments.
Host-feeding behavior was found to be steady throughout the lifetime of the parasitoid (mean longevity 31 days, ± 14.2). A mean 4.3 RWA (± 2.0) were killed per day by this behavior.
Available cage space was optimized when a parasitoid population of 100 (70% female) was used for mummy production. A host-to-parasitoid ratio of 80:1 was determined to be optimal when host ages (instars) were random. A mean 164 mummies (± 56) per female developed at this host-to-parasitoid ratio. This high host-to-parasitoid ratio made the host density in the cage the limiting factor rather than parasitoid density. At densities of 200 and 300 parasitoids, aphid numbers were too high for the plants to sustain them, and everything died as a result.
Short-term cold storage of A asychis mummies proved to be a feasible alternative to shipping mummies when conditions so dictate. Three population ages, 3, 7 and 21 days, were stored for periods of 3, 5, 7 and 14 days. Best percent emergence occurred for the 3-day old population, however, each age declined in emergence when stored for increasingly longer lengths of time. Lowest percentage emergence occurred for 21-day old mummies stored for 14 days. Twenty-one day old mummies exhibited higher percent emergence when stored for 3, 5 and 7 days than did the 7-day old mummy population. Males survived the cold storage process better than females, as most of the decrease in emergence at the longer storage times was indicated to be female mortality
Pan American University
Copyright 1992 Robin Whitaker-Deerberg. All Rights Reserved.