Espino L, Way M O, Pearson R, Nunez M
University of California Cooperative Extension, Colusa, CA 95932, USA.
J Econ Entomol. 2009 Aug;102(4):1536-45. doi: 10.1603/029.102.0418.
Results of planting date and insecticide efficacy experiments targeting Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae) on rice, Oryza sativa L., in southeastern Texas between 2002 and 2007 were used to determine density-yield relationships as a function of planting date. Soil core samples were collected on two dates during main crop development to estimate immature L. oryzophilus populations followed by main and ratoon crop harvests. Analysis of covariance (ANCOVA) revealed that planting date did not affect the density-main crop yield relationship during most years and that these relationships varied substantially among years. For ratoon crop yield, an effect of main crop L. oryzophilus immature infestation was detected during some years, but the real effect of these populations on ratoon crop yield remains unclear. Using estimates of yield reduction per L. oryzophilus immature, economic injury levels were calculated. Main crop yields from treated plots and first soil core sample L. oryzophilus immature populations from untreated plots were significantly higher in plots planted at recommended dates than in plots planted earlier or later. This suggests that the presence of high populations of reproductive L. oryzophilus coincides with the period when rice fields planted at optimum dates are flooded. Results from this study reinforce the importance of managing L. oryzophilus populations when planting rice at recommended dates in southeastern Texas.
2002年至2007年间，在得克萨斯州东南部针对水稻上的稻水象甲（鞘翅目：象甲科）开展了播种日期和杀虫剂药效试验，其结果用于确定作为播种日期函数的密度-产量关系。在主作物生长发育期间的两个日期采集土壤芯样，以估计未成熟稻水象甲的种群数量，随后进行主作物和再生作物的收获。协方差分析（ANCOVA）表明，在大多数年份，播种日期不影响密度与主作物产量的关系，且这些关系在不同年份间差异很大。对于再生作物产量，在某些年份检测到主作物稻水象甲未成熟虫口的影响，但这些种群对再生作物产量的实际影响仍不清楚。利用每头未成熟稻水象甲造成的产量损失估计值，计算了经济损害水平。在推荐日期种植的地块中，处理地块的主作物产量和未处理地块首次土壤芯样中的稻水象甲未成熟种群数量，均显著高于早播或晚播地块。这表明，大量繁殖期的稻水象甲出现时间与最佳日期种植的稻田被淹时期相吻合。本研究结果强化了在得克萨斯州东南部按推荐日期种植水稻时管理稻水象甲种群的重要性。
