ABSTRACT


Carlos Quiroz E.1
 
An experiment to evaluate the influence of three sowing dates and the effect of 4 species of cereal aphids on yield and yield components, by excluding them at different growth stages of wheat cv. Mexifen, was conducted at La Platina Experimental Station, INIA, in Santiago, Chile. Yields were significatively reduced on the latest sowing treatments, being the number of grains per head the most affected component. Earlier aphid arrivals and higher aphid population densities were abserved on younger stages of growth on the later sowing dates than on the early-sown treatment, being these conditions, as well as the shorter period of plant development, important factors of yield losses.
Plots protected with Pirimicarb each 10 days, yielded the same as the treatmemtsprayed from tillering to flag leaf fully developed. This fact could be closely relatedto aphid population densities, since the population peak was reached at flag leafstage. No protection during this period determined a reduction on grains per head andkernel weight.
By visual observation of virus symptoms on spikes, it could be concluded that allthe treatments were affected by BYDV with the same intensity.Hectoliter weight was low in all treatments, including permanent protection.Highly efficient activity of natural enemies, mainly the fungus Entomophthoraspp. and syrphid flies, was observed, specially since flag leaf stage.
Key words:
1Ing. Agr., Programa Cereales, Entomología, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.