Abstract
Synthetic pesticide use has been the dominant form of pest control since the 1940s. However, biopesticides are emerging as sustainable pest control alternatives, with prevailing use in organic agricultural production systems. Foremost among botanical biopesticides is the limonoid azadirachtin, whose perceived environmental safety has come under debate and scrutiny in recent years. Coconut production, particularly organic coconut production, is one of the agricultural systems in which azadirachtin is used as a primary method of pest control for the management of the invasive coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae). The management of this mite species also greatly benefits from predation by Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae). Here, we assessed the potential behavioral impacts of azadirachtin on the coconut mite predator, N. baraki. We explored the effects of this biopesticide on overall predator activity, female searching time, and mating behavior and fecundity. Azadirachtin impairs the overall activity of the predator, reducing it to nearly half; however, female searching was not affected. In contrast, mating behavior was compromised by azadirachtin exposure particularly when male predators were exposed to the biopesticide. Consequently, predator fecundity was also compromised by azadirachtin, furthering doubts about its environmental safety and selectivity towards biological control agents.
Highlights
The use of synthetic pesticides has been the dominant method of agricultural pest control since the early 1940s [1,2]
The duration spent in each level of activity, either inactive, or under slow or fast activity, varied significantly between azadirachtin-treated and untreated predatory mites (F1,14 7.97, P 0.01)
The length of time it took virgin male predatory mites to first find virgin females was subjected to analysis of variance; no significant difference was found between treatments (F3,76 = 1.54, P = 0.21)
Summary
The use of synthetic pesticides has been the dominant method of agricultural pest control since the early 1940s [1,2]. Azadirachtin arguably stands out as the most widely used botanical pesticide since the onset of synthetic pesticides for pest control, which is well established in organic agriculture, public health, home and garden, and selected agricultural settings [16,17] This biopesticide has unique features and can act as an arthropod anti-feedant, growth regulator and sterilant, while its safety to vertebrates is broadly recognized [11, 16]. Such a change in perception is the likely consequence of a shifting in focus, from reliance on acute lethal effects, to sublethal effects of insecticidal compounds [21,22,23] Phytophagous mites and their predators are a focus of attention regarding the sublethal impact of crop protection compounds, and regarding the effect that azadirachtin has on these species [24,25,26]. We assessed the potential sublethal behavioral effects of azadirachtin, at its label rate for controlling the coconut mite, and the potential consequences in the overall activity, mating and fecundity of the coconut mite predator N. baraki
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