Species of aphids observed on wheat in Rio Grande do Sul, their control and influence on production

Abstract

In 1971 in Pelotas and Passo Fundo (RS), a field experiment was conducted with wheat using granulated systemic insecticides, in emulsion and solution and selective contact aphicides, applied on the plant foliage when the aphids appeared; the principal objective was to determine the period of duration of their toxic effects in relation to the attack on these pests and their effect on yields. It was demonstrated that the use of granulated systemic insecticides in the aerial parts of wheat does not give the plant immediate protection, but they are more effective than selective aphicides that are efficient in the first 24 hours after application. The losses due to aphid injury at Pelotas were 19.6%, and in Passo Fundo where the attack was very intensive the losses were 31.5%. Macrosiphum (Sitobion) avenae F. was recorded on wheat in the state of Rio Grande do Sul for the first time. Metopolophium dirhodum (Walker), which had also been reported by Fehn (1970) in 1968, was encountered. Also the ubiquitous greenbug Schizaphis graminum (Rondani) was registered. The results indicate that these species of aphids do not appear in the same intensity each year. It was concluded that preventive methods were not necessary each year but rather to use insecticides only when aphid numbers so indicated.