Effectiveness and economics of rotenone for the control of insect pest vegetable

Conventional insect pest control mostly relies on the use of insecticide of synthetic origin. The synthetic insecticide is well documented for its adverse effect on the environment, spray operators and consumers. Interest on the use of biological insecticide as the alternative to the conventional insecticide has generated number of products of microbes and plant origin. The microbes are the most popular and fungi such as Paecilomyces fumosoroseus, Metarhizium anisopliae, Beauveria bassiana have been used as mycoinsecticides. On the other hand, botanical insecticide azadirachtin extracted from the seeds of Azadirachta indica is available locally for insect conrol. Apart from azadirachtin, the other candidate of botanica insecticide is rotenone. Rotenone in South East Asia is commonly found in the root of Derris species. It has been used by the farmers as an insecticide and piscicide. The farmers use crude extract of rotenone obtained by soaking the roots in water. Nevertheless, the extraction efficiency is generally poor leading to inconsistent or poor result of insect control. Extraction technique using methanol or acetone improved the yield of rotenone with extraction efficiency of up to 3.5%. Formulating the rotenone organic extract as emulsifiable concentrate and laboratory evaluation of its toxicity against Plutella xylostella shows the LC50 of 6.13 micro gram/mL. This value is lower compare with the LC50 of azadirachtin and chlorfenapyr being 12.11 and 10.37 micro gram/mL, respectively. This indicates better or comparable toxicity of rotenone as azadirachtin and chlorfenapyr. Field application of rotenone at 30 g a.i./ha gave similar level of control of Spodoptera litura compared with the standard spinosad. The cost of using rotenone is calculated to be about RM 240.00/hectare. The value is about similar to that of azadirachtin and spinosad. Derris species are abundant locally and relatively, easy to cultivate. They can be grown as intercrop with oil palm and rubber. This will be a plus factor from economic point of view in the utilization of rotenone as biopesticide.