ABSTRACT
Effect of the aphid-virus complex on wheat yield in the north central valley of Chile

Carlos Quiroz E.1
 
Research work has been carried out at La Platina Experimetnal Station, Santiago, Chile, in order to determine the impact caused by the aphid-virus complex on wheat production in the North Central Valley of Chile, during the seasons 1976-77 and 1977-78. Metopolophium dirhodum (Walker), Sitobion avenae (F), Rhopalosiphum padi (L.), Rhopalosiphum maidis (Fitch) and Schizaphis graminum (Rond), were the species found on the crop. All of them have been described as BYDV vectors. The monst abundant species in this zone is M dirhodum. Samples analyzed during these two years, inicated that aphids start appearing in early sptember on wheat fields sowed in normal date, reaching the highest populations in the second half of october, when the plants are between the growth stages 8 and 10 of the Feekes Scale, although population dinamics depends mainly on wheather conditions, rather independently of the plant growth stages. The aphid index, comparing 14 check plots, with the 14 correspondent totally protected plots, had an average value of 593.0, according to the formula of Rautapaa. This index meant about 19% yield loss, compared with the permanent protection treatments. The most important factor in this loss would be the direct damage of aphids, because permanent protection does not prevent virosis on plants. Some result about varietal performance and influence of seeding date on damage caused by this complex, are also given.
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1 Ing. Agr., Entomología Cereales, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.