The association of Sitophilus oryzae (Col.: Curculionidae) and Tribolium castaneum (Col.: Tenebrionidae) in the white rice: population growth and white rice deterioration

English. The association of Sitophilus oryzae (Lin.) (Col.: Curculionidae) and Tribolium castaneum (Herbst) (Col.: Tenebrionidae) in the white rice, IR64 variety, was studied in the laboratory. Objective of the study was to determine the influence of the association upon their population growth and the white rice deterioration. Adults of the two insect-pest species as many as (a) 50 S. oryzae, (b) 50 S. oryzae and 50 T. castaneum and (c) 50 T. castaneum were cultured on 0.5 kg of the white rice for two months period. The growth rate of the species was assumed to fit exponential pattern. The results showed that the growth rate of S. oryzae population when it was cultured together with T. castaneum was (r= 0.0475) significantly lower than it was cultured alone (r=0.0586), on the other hand, the growth rate of T. castaneum (r=0.0366) when it was cultured together with S. oryzae was significantly higher than it was cultured alone (r=0.0288). The presence of T. castaneum might cause an interference competition for S. oryzae, while broken rice as a result of S. oryzae attack might be a good food source for T. castaneum. The combination of attack of the two beetle species significantly reduced the white rice quantity and quality; it increased the broken rice, water content and mustiness

unknown. Pengaruh asosiasi Sitophilus oryzae (Lin.) (Col.: Curculionidae) dan Tribolium castaneum (Herbst) (Col.: Tenebrionidae) terhadap deteriorasi beras IR-64 dikaji di laboratorium. Imago kedua jenis hama tersebut sebanyak (a) 50 S. oryzae, (b) 50 S. oryzae dan 50 T. castaneum, dan (c) 50 T. castaneum, dipelihara pada 0,5 kg beras selama dua bulan. Laju pertumbuhan populasi kedua jenis hama tersebut diasumsikan mengikuti pola eksponensial. Hasil penelitian menunjukkan bahwa laju pertumbuhan populasi S. oryzae (r=0.0475) yang dipelihara bersama T. castaneum secara nyata lebih rendah daripada bila dipelihara sendiri (r=0.0586), sebaliknya laju pertumbuhan populasi T. castaneum (r=0.0366) yang dipelihara bersama S. oryzae secara nyata lebih tinggi daripada bila dipelihara sendiri (r=0.0288). Keberadaan T. castaneum diduga menyebabkan terjadinya kompetisi interferensi bagi S. oryzae, sedangkan serpihan beras akibat serangan S. oryzae sebagai sumber inang T. castaneum yang baik. Serangan kombinasi kedua hama tersebut secara nyata menurunkan kuantitas dan kualitas beras; beras patah, kadar air dan bau apek meningkat