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Browsing Theses by Author "Peterkin, Dorothy Dianne"

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    The effect of extracts from Serjania paucidentata (D.C.) on feeding, growth and mortality of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera : Noctuidae).
    (2012-06-22) Peterkin, Dorothy Dianne
    Green plants have developed protective secondary compounds or allelochemicals from evolutionary association with phytophagous animals. These chemicals occur in a range of chemical groups and may be toxins, antifeedants or insect hormone analogues which can be used in novel approaches to insect pest management. The extract from a local plant Serjania paucidentata contains saponins and is toxic to Brine Shrimp (ED50 = 0.32 mg/ml). The properties of S. paucidentata were investigated on the Fall Armyworm, Spodoptera frugiperda. The effect produced by the aqueous methanolic fraction and the crude extract were the same. These had ED50’s of 3.27 mg/ml and 2.355 mg/ml respectively when incorporated into a defined diet. A concentration of 11.43 mg/g diet produced 100% mortality in 10 days. Reduced feeding, decreased growth rates and pupal weights, and increased developmental periods were produced in S. frugiperda at sub-lethal doses. Insects were deterred from feeding on corn leaf squares treated with 1% extract in choice tests. Toxicity and antifeedant properties are dosage dependent. Typical of unpurified plant extracts, S. paucidentata extracts exhibited multiple modes of action as a stomach poison, antifeedant and possible growth retardant. Phytochemicals from local plants are unexplored resources, which must be documented and utilized. There is much scope in this area for further study.