Effects of Several Plant Leaves on Rice Weevil, Sitophilus oryzae (Coleoptera: Curculionidae) Productivity and Stored Rice Qualities

Abstract

Fresh, dried and powder forms from leaves of Murayya keonigii, Piper betel, Cymbopogon citratus, and Cosmos caudatus were tested for their repellent or attractant effects, developmental inhibition and infestation control towards Sitophilus oryzae in stored rice grain. A hundred of S. oryzae were released in the free choice bioassay chambers. The number of S. oryzae oriented within the chamber after three days exposure to different forms of the above leaves were counted and recorded. In no choice ovipositional test, five pairs of S. oryzae were introduced in separately treated rice grain (fresh and dried forms of leaves in 1g and powder leaves in 1% w/w) for five days. After four weeks, the number of newly emerged weevils were counted and compared. The repellent effect was showed in fresh form of M. koenigii with the less preferred by the weevils (10.00±2.08), dried (10.67±5.17) and powder form of C. citratus (17.00±3.00). Piper betel leaves showed an attractant effects toward the S. oryzae (20.33±9.82). The lowest number of new emergence was observed in rice grain treated with dried form of M. koenigii (0.33±0.33). In week 7, the powder form of M. koenigii still showed the lowest number of S. oryzae (32.00±19.50) while the highest showed in rice grain treated with powder form of C. citratus (127.33±32.75). The lowest weight of bore dust produce was observed in rice grain treated with powder form of M. koenigii (0.23g), followed by C. caudatus (0.40g), control (0.70g) and P. betle (1.17g). There is no significant difference in percentage of weight loss among the stored rice treated with different forms of the plant leaves were observed in this experiment (p >0.05).