Huib Tollenaar1 y Ruperto Hepp G.2

Transmission experiments with the aphid species Metopolophium dirhodum (Walker) demostrated that the red leaf condition of oats associated with blasting of spikeletes, chlorosis or red discoloration of wheat leaves as well as stunted, yellow barley plants, which are commonly observed in commercial plantings in central Chile, are attributed to barley yellow dwarf virus (BYDV).
Metopolophium dirhodum constitutes one of the major pests of reals in Chile and therefore should be considered as the principal vector of BYDV. Another potential vector of BYDV, Rhopalosiphum padi (L.), infests only corn under natural conditions. However, in greenhouse experiments R. padi possessed a transmission efficiency of 84.8 percent, while M. dirhodum transmited BYDV with an efficiency of 60.4 percent.
In the 1969-1970 growing season, yield reduction of "Chifen" and "Lilifén" spring wheat caused by BYDV was determined by sampling spikes of healthly and diseased plants in naturally infected plots. BYDV diminished yields of infected plants of "Chifen" and "Lilifén" by 30.6 and 46.6 respectively, while the 1000-kerned weight decreased 24.8 percent for "Chifén" plants and 2.2 percent for "Lilifén" plants.

1Ph. D., Fitopatólogo, FAO-INIA, Estación Experimental Quilamapu, Chillán. Profesor Extraordinario, Facultad de Agronomía, Universidad de Concepción. Casilla 537, Chillán, Chile.
2Ing. Agr. Dirección actual: Department of Plant Pathology, University of Wisconsin, Madison 53706, USA.