Movement ecology of adult western corn rootworm; implications for management

Authors: Sappington, Thomas; SPENCER, JOSEPH - University Of Illinois

Submitted to: Insects
Publication Type: Review Article
Publication Acceptance Date: 11/23/2023
Publication Date: 12/3/2023
Citation: Sappington, T.W., Spencer, J.L. 2023. Movement ecology of adult western corn rootworm; implications for management. Insects. https://doi.org/10.3390/insects14120922.
DOI: https://doi.org/10.3390/insects14120922

Interpretive Summary: The western corn rootworm is a destructive and mobile insect pest of corn in North America and Europe. It is difficult to manage, in part because of its penchant to evolve resistance to many forms of control. Understanding spatial patterns and distances of adult flight is critical to improving pest and resistance management strategies. However, a holistic understanding of adult rootworm movement has remained elusive because of conflicting observations of short- and long-distance lifetime dispersal, a type of dilemma in ecology called Reid’s Paradox. Estimates of gene exchange between populations provide indirect estimates of dispersal distances suggesting movement that is much farther than that measured by direct field observations, a similar type of dilemma called Slatkin's Paradox. Taken together, the evidence is clear that many individual rootworms do not travel very far in their lifetime, often laying eggs in the same field they emerge in. But a substantial number of others take long flights of many kilometers before leaving offspring. We conclude that western corn rootworm is a partially migratory species consisting of two distinct behavioral types, "residents" and "migrants". This interpretation will be useful in improving models of rootworm population dynamics and devising better rootworm pest management methods.

Technical Abstract: Movement of adult western corn rootworm, Diabrotica virgifera virgifera LeConte, is of fundamental importance to this species' population dynamics, ecology, evolution, and interactions with its environment, including cultivated cornfields. Realistic parameterization of dispersal components of models is needed to predict rates of range expansion, development and spread of resistance to control measures, and improve pest and resistance management strategies. However, a coherent understanding of western corn rootworm movement ecology has remained elusive because of conflicting evidence for both short- and long-distance lifetime dispersal, a type of dilemma observed in many species called Reid’s Paradox. Attempts to resolve this paradox using population genetics strategies to estimate rates of gene flow over space likewise imply greater dispersal distances than direct observations of short-range movement suggest, a dilemma called Slatkin's paradox. Based on the wide-array of available evidence, we present a conceptual model of adult western corn rootworm movement ecology under the premise it is a partially migratory species. We propose that rootworm populations consist of two behavioral phenotypes, "resident" and "migrant". Both engage in local, appetitive flights, but only the migrant phenotype also makes non-appetitive migratory flights, resulting in observed patterns of bimodal dispersal distances, and resolution of Reid's and Slatkin's paradoxes.