Palumbo J C, Toscano N C, Blua M J, Yoshida H A
University of Arizona, Department of Entomology, Yuma Valley Agricultural Center, 85364, USA.
J Econ Entomol. 2000 Dec;93(6):1688-94. doi: 10.1603/0022-0493-93.6.1688.
A 3-yr project was initiated in 1993 to examine the effects of insecticides and sustained whitefly, Bemisia argentifolii Bellows & Perring [aka. B tabaci Gennadius (Strain B)], feeding on alfalfa plant growth and vigor in greenhouse cage studies, and to determine the impact of natural Bemisia whitefly populations on alfalfa forage yields and quality in a large-plot field experiment. Alfalfa plant growth and vigor after exposure to imidacloprid and a mixture of fenpropathrin and acephate insecticides did not differ from untreated plants in the greenhouse. Consequently, foliar and soil applied insecticides were used to manipulate whitefly densities on alfalfa plants to measure whitefly feeding effects on plant growth and forage yield. Heavy whitefly densities on untreated alfalfa plants in the greenhouse resulted in significant reductions in relative growth rates and net assimilation rates as compared with imidacloprid-treated plants that were maintained relatively whitefly-free. Reductions in alfalfa plant growth measured between infested and treated plants were proportional to whitefly densities. Field plot results derived from three crop seasons were relatively consistent with our greenhouse trials. Both experimental approaches clearly showed that alfalfa plants exposed to high densities of whitefly immatures and adults grew at a significantly slower rate and produced less foliage. As a result of reduced growth rates, alfalfa maturity in the naturally infested plots was estimated to be approximately 7-10 d behind managed plots. Delays in maturity resulted in significant reductions in forage yields of 13-18% during August-September harvests when whitefly populations reached peak abundance. Whitefly feeding stresses also effected hay quality through the reduction of crude protein content and contamination of foliage with honeydew and sooty mold. The status of the Bemisia whiteflies as an economic pest to alfalfa is clearly evident from these studies, but the damage potential of whiteflies in the southwestern United States appears to be restricted to one or two harvest periods during the summer coinciding with peak adult populations and their dispersal from alternate host crops.
1993年启动了一个为期3年的项目，在温室网笼试验中研究杀虫剂和持续存在的烟粉虱（Bemisia argentifolii Bellows & Perring，又名B tabaci Gennadius（B型））取食对苜蓿植株生长和活力的影响，并通过一个大面积田间试验确定自然烟粉虱种群对苜蓿牧草产量和质量的影响。在温室中，接触吡虫啉以及甲氰菊酯和乙酰甲胺磷杀虫剂混合物后的苜蓿植株生长和活力与未处理植株没有差异。因此，使用叶面喷施和土壤施用的杀虫剂来控制苜蓿植株上的粉虱密度，以测定粉虱取食对植株生长和牧草产量的影响。与保持相对无粉虱的吡虫啉处理植株相比，温室中未处理苜蓿植株上的高密度粉虱导致相对生长率和净同化率显著降低。在受侵染植株和处理植株之间测得的苜蓿植株生长减少量与粉虱密度成正比。来自三个作物季节的田间小区试验结果与我们的温室试验结果相对一致。两种试验方法都清楚地表明，暴露于高密度粉虱若虫和成虫的苜蓿植株生长速度明显较慢，叶片产量较低。由于生长速度降低，自然受侵染小区的苜蓿成熟期估计比管理小区晚约7 - 10天。当粉虱种群数量达到峰值时，成熟期延迟导致8 - 9月收获期的牧草产量显著降低13 - 18%。粉虱取食压力还通过降低粗蛋白含量以及使叶片被蜜露和煤烟霉污染而影响干草质量。从这些研究中可以明显看出烟粉虱作为苜蓿经济害虫的地位，但美国西南部粉虱的潜在危害似乎仅限于夏季与成虫种群高峰期及其从替代寄主作物扩散相吻合的一两个收获期。
