イネクビボソハムシの要防除密度推定に関する研究 III : 要防除密度と防除要否判定のための密度推定法

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書誌事項

タイトル別名
  • Threshold Density of the Rice Leaf Beetle, <i>Oulema oryzae</i> KUWAYAMA, for Insecticidal Control.
  • イネクビボソハムシの要防除密度推定に関する研究
  • イネクビボソハムシ ノ ヨウボウジョ ミツド スイテイ ニカンスルケンキュウ
  • III. Control Threshold Density and Sampling Size
  • III. 要防除密度と防除要否判定のための密度推定法

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抄録

In Niigata Prefecture, larvae of the rice leaf beetle injured rice leaves from the beginning to the end of June, and reduced the yield of rice. The best time for controlling this pest with insecticides was when hatching of the larvae was at its peak, which corresponded to the 4th-5th day after the peak of oviposition. On the basis of the relationship between the damage caused by the 3rd and 4th instar larvae and the survival rates from egg to the 3rd instar, the control threshold density, as determined by the peak egg density at the beginning of June, was about 8 eggs per hill. The eggs were laid in masses on rice leaves, and the masses were distributed randomly in a paddy field. The practical sample size required for determining the control threshold of eggs, with a reasonable precision was 36 hills per paddy field (18 points×2 hills). On the other hand, the control threshold in terms of the peak density of immigrated adults in the paddy field was estimated at about 0.1 beetles per hill. The best time for insecticide application coincided with the 10th day of peak adult density. But, this control threshold value was less precise as compared with that obtained for the eggs. The distribution of the adults in the paddy field was aggregated. The sample size required for making a decision on insecticide application was 100 hills (4 points×25 hills) per paddy field for adults.

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