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Development of a botanical insecticide from Ambon and surrounding areas (Indonesia) for local use Leatemia, Johanna Audrey

Abstract

Intensive use of synthetic insecticides to control insect pests had lead to many problems such as pest resistance and resurgence, effects on non-target organisms, human exposure and environmental impacts. These negative effects have provided the impetus for the development of alternatives including botanical insecticides. Some tropical plant families (e.g. Meliaceae and Annonaceae) have been shown to possess promising insecticidal properties. The general objectives of this study were to identify sources of botanical insecticides from plants growing in Ambon and surrounding areas (Indonesia) that might be of value for commercial development, and to develop simple methods of production for local use in these areas. Crude ethanolic seed extracts of Annona muricata L, A. squamosa L. (Annonaceae), Lansium domesticum Corr., and Sandoricum koetjape (Burm. F.) Merrill (Meliaceae) collected from different locations and years in Maluku, Indonesia, were screened for inhibition of larval growth against the polyphagous lepidopteran, Spodoptera litura (Fabr.). Extracts of A. squamosa were the most active ones. These extracts were significantly more active (20-fold) than A. muricata. There were geographic as well as annual differences among the extracts of both species. Extracts of L. domesticum and S. koetjape did not show sufficient bioactivity to be considered further. Laboratory evaluation was carried out to assess the efficacy of the promising extracts. Aqueous emulsions of ethanolic seed extracts and crude aqueous seed extracts of A. squamosa were tested via bioassays against the diamondback moth Plutella xylostella L. and the cabbage looper, Trichoplusia ni (Hubner). The extracts showed toxic as well as antifeedant effects against both species. Greenhouse trials were conducted to assess the efficacy of the extracts against diamondback moth larvae. Toxicity of crude aqueous extracts was evaluated against some commercially available biocontrol agents. An aqueous emulsion of an ethanolic seed extract at a concentration of 0.5% (w/v) was more (2.5 fold) effective than 1 % Rotenone, a commercial insecticide. Crude aqueous seed extracts showed efficacy comparable to pyrethrum (0.1% a.i), a widely used botanical insecticide. Chrysoperla carnea (Stephens) larvae were the least susceptible to the extracts followed by Orius insidiosus (Say.) adults, while Trichogramma brassicae (Bezd) adults were the most susceptible. A preliminary economic analysis was conducted to evaluate the feasibility of producing the crude aqueous seed extracts as a botanical insecticide for local use. Production and utilization of crude aqueous seed extracts of A. squamosa was just slightly more economical than using synthetic insecticide. Good efficacy of crude seed extracts of A. squamosa both in the laboratory and the greenhouse against lepidopteran pests and a slight economic benefit will make this species a promising candidate for development as a simple botanical insecticide for local use in Ambon (Indonesia).

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