ChileanJAR

The influence of time of planting on grain yield was determined in relation with the presence of the aphid Metopolophium dirhodum (Walker) in seven field experiments with spring wheat at Chillan, Linares and General Lopez (Carillanca) , during the years 1969-71.
The effect of planting date and the incidence of aphids on grain yield was studied by means of field experiments set in an Split Plot designo To study the date of planting and aphid effect on yield and cultivars, the Split-Split-Plot design was used.
M. dirhodum affected grain yield, seed weight and seed number per spike, plant height and flag leaf area. Aphid damage increased as date of planting was delayed. Planting date affected grain yield, seed weight, seed per spike and plant height. Cultivar Menflo was the least affected by M. dirhodum and Huelquen was more tolerant when the time of planting was changed.
Fungi of Entomophthora were observed affecting the aphids; the level of parasitism reached 90 percent, after the aphid population increased notably in number. The most important predators were syrphids of the genus Allograpta and the coccinellid Eriopis connexa (Germar). The efficiency of them in controlling the aphids was not measured. Other less important predators detected were the coccinellids Adalia bipunctata L. and A. deficiens Mulsant.