INFLUENCE OF WATER AND NITROGEN-FERTILIZER ON BIOLOGY OF THE RUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE) ON WHEAT

The effect of water and nitrogen (N) fertilizer on densities of Russia n wheat aphid, Diuraphis noxia (Mordvilko), on field-grown wheat was d etermined. Aphid densities were not significantly different (p < 0.05) among fertilizer rates (0-134 kg N ha(-1)). There were significantly (p < 0.05) more aphids from 22 March to 4 April 1988 on wheat that was not irrigated than on wheat irrigated four times during the growing s eason. More than 60 cm of rain fell during April and aphid numbers wer e not significantly different (p < 0.05) between irrigation treatments until 17 May 1988. By then, plants were stressed in the plots that we re not irrigated and aphid densities were again higher than on plants in the plots that had been irrigated four times. Significantly (p < 0. 05) more Russian wheat aphids were found on wheat plants grown in lysi meters maintained at 15% soil water holding capacity (SWHC) in a raino ut shelter than on plants in lysimeters maintained at 50 and 100% SWHC .