Carlos Quiroz E.1
In order to ensure the success of artificial infestations with viruliferous aphids on genetic test material for Barley Yellow Dwarf Virus (BYDV), studies were carried out at the La Platina Exp. Sta. (INIA, Santiago), in the 1984/85 and 1985/86 seasons. In those treatments where the methylcarbamates Carbofuran and Methiocarb were used, the aphids' populations were at least twice that in the control plots, showing a lower effect of syrphids and para· sitoids on the aphids. This indicates the action of methylcarbamates on the natural enemies of the aphids, without incidence on the pest development. No statistical differences were observed in yield and hectol iter weight, between the carbamate treat· ments and the control, although a lower 1.000 kernel weight was achieved in the treated plots. As viruliferous aphids were used for the infestation, reaching an aphid-index higher than 200 in all the treatments, with exception of the one with permanent chemical protection, the yield losses observed in relations to protected plots were mainly the effect of the virus. It was concluded that the use of methylcarbamates ensures higher aphid populations than in naturally infested plots, by con· trolling its natural enemies and permitting the success of the infestation, under conditions unfavorable to the development of the pesto
1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3, Santiago, Chile.