Effects of Potato Leafhopper, Empoasca fabae (Harris), and Water Stress on Alfalfa Forage Yield and Quality

Abstract

Field experiments were conducted at two locations, Becker and Rosemount, Minnesota, USA, from 1986 through 1988. The major objective is to determine the individual and interacting effects of potato leafhopper and water stress on alfalfa yield and quality. In these experiments, increases in potato leafhopper infestation consistently reduced yield. High potato leafhopper densities were required to cause decrease in plant height. On most cuttings. potato leafhopper had no effect on leaf:stem ratio. High potato leafhopper densities caused decreased herbage digestible dry matter. Moderate water stress status usually did not affect potato leafhopper distribution in the field. Water stress consistently decreased alfalfa yield. Plant height decreased when alfalfa was grown under water stress. Leaf to stem ratio was not affected by moderate water stress. Alfalfa quality was little affected by moderate water stress. Water deficit caused earlier alfalfa flowering, but potato leafhopper did not significantly affect maturity of alfalfa. Significant interactions between yield or yield value and water or potato leafhopper treatments did not occur frequently. 馬鈴薯姬葉蟬(Empoasca fabae)為美國苜蓿和馬鈴薯之主要害蟲。本試驗自1986至1988年，分別於美國明尼蘇達州的Becker和Rosemount兩地進行。主要的目的在探討馬鈴薯姬葉蟬和水對苜蓿產量及品質的效應及此兩因子之交感作用。結果顯示增加馬鈴薯姬葉蟬為害導致苜蓿減產，較高的葉蟬族群密度方足以降低株高。大部份的結果顯示葉對莖的重量比並不受此害蟲的影響。高馬鈴薯姬葉蟬密度減少植株可消化性乾物質之百分率，苜蓿中度缺水並不會影響葉蟬的田間族群分布。缺水導致苜蓿減產，株高也降低但是葉對莖重量比不受影響。苜宿的品質在中度缺水情況下仍不受影響。馬鈴薯姬葉蟬和水對產量和品質之交感作用並不經常發生。苜蓿缺水會造成提早開花但是馬鈴薯姬葉蟬並不影響苜蓿之成熟期。