Relationship between the number of Leptocorisa chinensis Dallas (Hemiptera: Alydidae) and pecky grains, and factors affecting the relationship in rice fields
2005
Takeuchi, H.(National Agricultural Research Center, Tsukuba, Ibaraki (Japan)) | Watanabe, T. | Ishizaki, M. | Ma, D.L. | Suzuki, Y.
In order to clarify the relationship between the number of rice bugs, Leptocorisa chinensis, and number of pecky rice grains, we released eggs of the rice bugs, number ranging from 6 to 36, into 1.6 x 1.6 x 1.5m cages covered with 1 polyethylene mesh (1mm) at the milk ripening stage in a rice field. The numbers of hatched nymphs were estimated from the remaining egg shells. The actual number of rice bugs was counted at harvest time. Damaged pecky grains having a thickness of over 1.8mm were counted in each cage after harvest. The number of pecky grains correlated highly with the number of hatched nymphs and rice bugs at harvest time, but not with the number of eggs released. The number of hatched nymphs correlated highly with the number of rice bugs at harvest time, but not with the number of eggs released. The egg survival rate was bimodal with peaks at 0-20 or 80-100%, suggesting that predators caused an all-or-none type mortality to the eggs masses. These results indicate that the estimation of the density of hatched nymphs is more important than those of immigrant adults in order to obtain a highly accurate estimation of pecky rice damage in rice fields.
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