苜蓿斑蚜危害苜蓿的产量损失及防治指标的研究

The Effect of Therioaphis Trifolii on Alfalfa Yield and Control Index

采用人工接虫的方法,研究了苜蓿斑蚜的虫口密度与苜蓿产量损失之间的关系和防治指标。结果表明,苜 蓿干草产量损失率(y)与20枝条虫量(x)的关系为y=0.035 9x-5.993 9,相关系数r为0.993 1,二者相关性极显著。按 照防治的直接收益与直接成本,确定了宁夏旱地苜蓿和水地苜蓿苜蓿斑蚜的防治指标,旱地苜蓿第一茬苜蓿斑蚜的防治 指标为2 100头/百枝条,水地苜蓿第二茬苜蓿斑蚜的防治指标是1 600头/百枝条。

By artificially modifying the density of Therioaphis trifolii, the yield loss of alfalfa and control index of Therioaphis trifolii was carried out. Meantime, a correlative formula between population density of Therioaphis trifolii per 20 stems (X) and yield loss rate of dried hay (Y) was expressed as: Y=0.0359X-5.9935, its correlation coefficient r=0.9931. Based on the direct benefit and control cost, the economic threshold of controlling Therioaphis trifolii at various alfalfa fields were determined: 2100 aph-ids per 100 stems of the first crop in dry alfalfa field, 1600 aphids per 100 stems of the second crop in irrigated alfalfa field.