Dust to weevils, weevils to dust: maize weevil personality and susceptibility to diatomaceous earth

Abstract

The role of behavior in insecticide susceptibility is broadly recognized, in addition to the physiological effects of insecticides. Curiously, the recognition of the importance of behavior does not extend to the control by physical agents, like inert dusts such as diatomaceous earth (DE). Furthermore, behavioral traits are typically regarded as isolated traits and not as suite of traits simultaneously expressed in individual organisms, referred to as personality (or individuality). Because the set of behavioral traits of an individual may play a role in susceptibility to physical control agents, such as DE, a set of six behavioral traits encompassing three personality dimensions (i.e., activity, boldness/shyness, and exploration/avoidance), were assessed in six populations of the maize weevil Sitophilus zeamais. The (average) behavioral types varied among populations (Wilks´ lambda = 0.09, F 45/674 = 10.72, P < 0.001), as did the susceptibility to DE (χ2 = 11.0, df = 5, P = 0.05), with median survival times (95 % CL) ranging from 144.00 (119.69–168.31) h to 216.00 (179.10–252.90) h. These different behavioral types were not recognized when individual-based analysis was performed, although the individual hierarchical level represented over 63 % of the variance in the behavioral traits. Weevil activity was successfully used to describe survival time and, therefore, the susceptibility to diatomaceous earth, but the population-based response was crudely oversimplified. Therefore, to disregard the inter-individual behavioral variation, even when simple behavioral traits suitably describe the susceptibility to DE, in favor of interpopulation variation is temerary and may lead to management shortcomings.