ABSTRACT
Population fluctuation of Diuraphis noxia and its natural enemies in wheat crops at in the area of Bahía Blanca, Argentina

M. E. Reviriego1, L. R. Descamps1* y A. A. Ferrero1
 

The Russian wheat aphid Diuraphis noxia Mordvilko (Homoptera:Aphididae) is a dangerous pest of economic importance to the Argentina´s wheat growing region, dating from its appearance in 1991. Fluctuations in D. noxia population and its natural enemies were evaluated in the area of Bahía Blanca, Buenos Aires , Argentina, during 1994 and 1995. The information was obtained through direct plant sampling, water and soil traps and net catches. The first aphids were found in September during the phenological reed stage and the highest density was found in November during the phenological tassel stage. The age structure of the population was similar and was represented by young juvenile and adult forms. The population fitted an added type of pattern, constituted mainly of small pupa. The winged forms were found at the end of November, starting at that time their migration to natural grass. The alternative hosts were, Hordeum leporinum Link, Lolium multiflorum Lam., L. perenne L., Bromus unioloides Kunth, and Bromus brevis Nees. The most outstanding predators during both years of study were the Coccinelidae, Eriopis connexa (Mulsant), Hippodamia convergens (Guer.) and Coccinella ancoralis (Germ.) which presented together with Hymenoptera: Aphidiidae the peak of the maximum occurrence simultaneous to the aphid’s highest maximum population density. The presence of Diptera: Syrphidae and Nabis spp. was scarce.

Keywords: Russian wheat aphid, predators, parasitoids, population density, alternative plant hosts.
1 Universidad Nacional del Sur, Departamento de Agronomía, 8000 Bahía Blanca, Argentina. E-mail: descamps@criba.edu.ar. *Autor para correspondencia.