草地螟和黄草地螟危害苜蓿产量损失及防治指标的研究

采用人工接虫的方法,研究了草地螟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=4.936 6x-0.850 9,相关系数r为0.994 3,二者相关性极显著.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草地螟的防治指标,旱地苜蓿刈割2和3次的草地螟的防治指标分别是10和14头/100枝,水地苜蓿草地螟的防治指标是7头/100枝.依据同样的试验方法,制定了黄草地螟危害苜蓿的防治指标,旱地苜蓿刈割2和3次的黄草地螟的防治指标分别是45和60头/100枝,水地苜蓿黄草地螟的防治指标是36头/100枝.

Studies on the yield damage and economic threshold of Loxotage stictalis and Loxotage verticalis to Medicago sativa

By artificially modifying of the density of Loxotage stictalis, test on the yield damage and economic threshold of L. stictalis to Medicago sativa was carried out. A correlation formula between population density of L. stictalis per 20 stems (x) and yield loss rate of dried hay (y) was formed: y=4.936 6x-0.850 9,r=(0.994 3), which has significant relativity. Based on the direct benefit and control cost, the economic thresholds of controlling L. stictalis at various M. sativa field levels were determined as follow: 10 per 100 stems of the two cutting times and 14 per 100 stems of the three cutting times in dry M. sativa field; 7 per 100 stems in irrigated M. sativa field. Using the same experimental method, the economic thresholds of controlling L. verticalis were determined as well: 45 per 100 stems of the two cutting times and 60 per 100 stems of the three cutting times in dry M. sativa field; 36 per 100 stems in irrigated M. sativa field.