Control threshold of the rice reaf roller moth, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae) using leaf color and adult density
1998
Kawamura, T. (Yamaguchi-ken. Agricultural Experiment Station (Japan)) | Izumi, K.
The influence of infestation of Rice leaf roller moth from the panicle formation stage to heading time on the yield of rice was investigated. The control threshold based on the leaf color of the paddy rice and the number of imago in the the paddy field was examined. High negative correlation between damaged leaf percentage by cutting the lamina and the yield was found. The damaged leaf percentage with a tolerable 5% yield decrease percentage injury level was 26.1%. The correlation of the leaf color meter value in the peak number of imago and the damaged leaf percentage at about 3 weeks after the peak number of imago was high. The leaf color value corresponding to the damage leaf percentage of 26.1% from the regression formula Y = 4.26X - 106.8 was estimated to be 31.0 in the leaf color meter. As the correlation of the value of the leaf color meter and the leaf color board was high, it was possible to change the value of leaf color meter and the leaf color board from the regression formula Y = 0.146X + 0.658. The value of leaf color board corresponding to damaged leaf percentage of 26.1% was 5.0. The correlation of the damaged leaf percentage at about 3 weeks after the peak number and the number of imago in the maximum level was high. The number of the imago corresponding to damaged leaf percentage of 26.1% from the regression formula Y = 0.92X + 4.93 was 1.2/square meter
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