Sitophilus zeamais Motschulsky is the most important issue of rice storage as it decreases quality and quantity of the rice product. To replace dangerous chemical pesticides to resolve such problem, extracting natural substance to use as organic pesticide is thus explored and has gained momentum due to its safety and biodegradability. The natural substance could be derived from parts of plants such as seeds, fruits, shells, and rhizome. Essential oil extracted from plants are believed to repel insects in various ways for example killing the insects and inhibiting the egg-laying or feeding or growth. For these reasons, using natural substance from plant is a viable option to control insects in rice storage as it would be safe to rice products and the environment.
Study the effect of 5 types of oils extracted from black pepper, turmeric, clove, citronella, and elephant neem. Adult Sitophilus zeamais Motschulsky were released onto a dish lined with a circle paper, half of which the oil had been applied at multiple levels of concentration, while the other side contained no oil (picture 1). Number of insects on each half is counted to figure out percentage of repellence at a different time.
Study reveals that black pepper oil is the most effective repellent for Sitophilus zeamais Motschulsky (90.11%) while turmeric came in second (89.44%), followed by elephant neem (73.22%), citronella (62.34%), and clove (49.89%) in that order. After 12 hours of testing, it has been confirmed that black pepper oil, turmeric oil, and elephant neem oil are best repellents against the insect.