<i>Diuraphis noxia</i>: reproductive behaviour in Argentina

Abstract

Diuraphis noxia (Kurdjumov) (Rhynchota Aphididae) is an important aphid pest of wheat and barley crops in many countries. Populations of Russian wheat aphid (RWA) from different origins show different reproductive behaviour, but the situation in Argentina was unknown. The aim of the current research was to determine the reproductive behaviour of RWA in Argentina based on samples from populations at six different localities with contrasting land use, altitude and climate. RWA were collected from cultivated and wild grasses from February to December 2005, and 10-15 colonies of aphids were established by collecting parthenogenetic adult females from each population. These colonies were kept under natural conditions at La Plata (36°36′ South Latitude) from 21 December 2005 to 21 December 2007. In more than half of the colonies, oviparous females and eggs were recorded in both years when temperatures were low and the photoperiod either short or increasing and relatively long. Consequently, oviparous females and eggs were recorded from early autumn (April) until the following spring (October), when day length was 11:33 and 13:44 hours, respectively. In both years the temperature and the altitude at the place of origin were highly correlated with the timing of sexual development. The production of eggs enables RWA to survive periods of adverse conditions and generate variability. Thus, by reproducing sexually, RWA may be able to adapt to new environmental conditions and give rise to new, more aggressive biotypes, which can overcome the current resistant varieties of wheat.