Simulation of Russian wheat aphid movement and population dynamics on preferred and non-preferred host plants

Abstract

A computer simulation model was developed to investigate spatial and population dynamics of apterous Russian wheat aphids ( Diuraphis noxia) on preferreed (wheat) and non-preferred (oat) hosts. The location, development, reproduction, movement, and mortality of individual aphids within a population were predicted at simulated one-day time steps. Reproductive rate and mortality were modeled as stochastic processes, which were functions of both aphid chronological age and host favorability. An index of host favorability wwas established for each plant in a 25× 25-plant grid containing wheat oats. Host favorability was dependent on host species and aphid density on that plant. Aphid movement was modeled as a stochastic process, with probability of movement dependent on insect age and host plant favorability. The distance moved was proportional to the density of aphids on the plant the aphid was leaving, with random direction of movement. The model was calibrated with data from experiments in which Stephens wheat or Border oat plants in growth chambers were infested with adult female aphids, and populations monitored after 0, 3, and 7 days. Ability of the model to predict observed populations and plant infestation after 14 and 21 days was then tested. Use of the model to generate predicted spatial patterns of aphids on differential hosts is discussed.