Population fluctuation and losses caused by Tribolium castaneum (Herbst.) in different rice varieties under laboratory conditions

The studies were carried out on the population fluctuation and losses caused by red flour beetle, Tribolium castaneum (Herbst) in different rice varieties under laboratory conditions at Department of Entomology, Sindh Agriculture University Tandojam during August to December 2000. Four rice varieties viz. DR-83, Khara Gunja, Irri-6 and Kernai Basmati were used for the experimental purpose. The standard weight of each variety used in this experiment was 200 grams, kept in one-kilogram capacity plastic jars covered with muslin cloth and banded with rubber strips. The experiment was replicated four times and ten pairs of same aged adult beetles were released in each jar. Observations were taken from 19th August to 30th December at weekly interval and alive beetles were recorded. The grain weight loss percent in each variety caused by this beetle was calculated at the end of the experiment. The temperature and relative humidity was recorded daily during the entire period of study. The results on population fluctuation of red flour beetle as it harbored the highest beetle population (50.58 beetles). This was followed by Irri-6 (34.48 beetle, Kernal Basmati (28.59 beetles) and DR-83 (12.56 beetles), respectively. Whereas, the results on the percent weight loss in rice varieties showed that there was significant variation amongst all the rice varieties used in present studies. The percent weight loss was significantly higher and Khara Gunja (28.99%) followed by DR-83 (1.43%), respectively. Rice variety Khara Gunja was statistically most susceptible to red flour beetle as it harbored highest beetle population. DR-83 was recorded less attacked by red flour beetle and found resistant to pest attack. The grain weight loss was significantly higher in Khara Gunja, followed by Irri-6, Kernal Basmati and DR-83, respectively. The laboratory temperature 30 degree centigrade and above with relative humidity 62% was recorded favorable for multiplication of beetles. In the light of the above results it is recommended that rice variety Khara Gunja should be stored separately from other rice varieties with adequate measures for their protection. The fresh seed may be dried before preservation in the containers. Further studies on the resistance mechanism and chemical analysis are recommended.