AGE-SPECIFIC LIFE TABLE MODELING OF THE RUSSIAN WHEAT APHID (HOMOPTERA, APHIDIDAE) ON BARLEY GROWN IN BENZIMIDAZOLE AGAR

Age-specific life table studies were conducted on the Russian wheat ap hid, Diuraphis noxia (Mordvilko), to evaluate the effects of using a b arley-benzimidazole agar system on D. noxia growth, reproduction, and survival. Weibull functions, linear and nonlinear regression, a modifi ed Sharpe and DeMichele biophysical model (MSDBM), and Maxima function s were used to estimate or model survivorship patterns, the lower temp erature threshold for development, the upper temperature inhibition th reshold, nonlinear aspects of rates of development, and mean daily fec undity patterns of D. noxia, respectively. The Weibull function provid ed a good fit to the aphid survivorship patterns (R(2) = 0.95). The lo wer developmental threshold and the upper temperature inhibition thres hold for the Russian wheat aphid using the barley-benzimidazole agar s ystem were estimated to be 5.2 and 30.3 degrees C, respectively. The M SDBM also provided an excellent fit to nonlinear aspects of developmen tal rate trends (R(2) = 0.996). Maxima functions were found to adequat ely describe patterns of daily fecundity at 3 of the 4 constant temper atures examined. The mean longevity of D. noxia reared on the barley-b enzimidazole agar system was greater than those reported by other auth ors using wheat- and rye-benzimidazole agar systems. Longer nymphal de velopment times using the barley-benzimidazole agar system resulted in a lower intrinsic rate of increase for Russian wheat aphids reared at 19.5 degrees C, than those observed by other authors using wheat- and rye-benzimidazole agar systems, and a developmental threshold that wa s higher than those reported by other authors for Russian wheat aphids grown on wheat using other plant growth systems.