Guido Herrera M.1 y Carlos Quiroz E.1
A set of 10 wheat cultivars was maintained on trials during 10 growing seasons. The cultivars were subjected to two treatments: with and without insecticide. This way, the natural incidence of the barley yellow dwarf virus (BYDV), from 1976 to 1985, was studied. At the same time, some population indexes of the aphid veetors under field conditions were studied. The experiments indicated an average loss of 10.1% in yield for the 10 years periodo In four (1976, 1977,1978, and 1982) of the 10 years, these losses were statistically significant. Also, a change in the relative abundance of the vector species was detected. At the beginning of the period, Sitobion avenae and Metopolophium dirhodum were the most abundant vectors; on the other hand, Ropalosiphum padi increased from 2.0%, in 1976, to 80.3%, in 1981. The effects of these changes are discussed.
1 Estación Experimental La Platina (lNIA), Casilla 439, Correo 3, Santiago, Chile.