Evaluating the link between predation and pest control services in the mite world

Abstract

Pest regulation by natural enemies has a strong potential to reduce the use of synthetic pesticides in agroecosystems. However, the effective role of predation as an ecosystem service remains largely speculative, especially with minute organisms such as mites. Predatory mites are natural enemies for ectoparasites in livestock farms. We tested for an ecosystem level control of the poultry pest Dermanyssus gallinae by other mites naturally present in manure in poultry farms and investigated differences among farming practices (conventional, free‐range, and organic). We used a multiscale approach involving (a) in vitro behavioral predation experiments, (b) arthropod inventories in henhouses with airborne DNA, and (c) a statistical model of covariations in mite abundances comparing farming practices. Behavioral experiments revealed that three mites are prone to feed on D. gallinae. Accordingly, we observed covariations between the pest and these three taxa only, in airborne DNA at the henhouse level, and in mites sampled from manure. In most situations, covariations in abundances were high in magnitude and their sign was positive. Predation on a pest happens naturally in livestock farms due to predatory mites. However, the complex dynamics of mite trophic network prevents the emergence of a consistent assemblage‐level signal of predation. Based on these results, we suggest perspectives for mite‐based pest control and warn against any possible disruption of ignored services through the application of veterinary drugs or pesticides.

No deleterious effect of inundative releases of biological agents on native arthropod assemblages in poultry farms: A mesocosm experiment

“…In addition, abundances of Cheyletus spp. and A. casalis covaried with that of D. gallinae in farm buildings, suggesting trophic relationships between populations of these two predators with D. gallinae in the field (Roy et al, 2020). These two studies used Cheyletus samples from the same source buildings as in the present experiment, and thus dealt most likely with the species C. malaccensis.…”

“…are also among the most frequent and abundant predatory taxa in poultry manure and litter (Brady, 1970;Roy et al, 2017) and engage in reciprocal predation in vitro (Zriki et al, 2020). While the ecosystem service of regulation by native predators in laying hen farms has not been unambiguously demonstrated, the existence of interactions between predators and D. gallinae in the field suggests that it may exist (Roy et al, 2020).…”

Population‐level impact of native arthropod predators on the poultry red mite Dermanyssus gallinae

“…had been shown in vitro to prefer D. gallinae to the alternative prey Astigmata (Roy et al, 2020;Zriki et al, 2020). This apparently contradictory result may be due to behavioral differences between the two species: astigmatic mites are very slow-moving mites, whereas D. gallinae is swift and often active.…”

“…The potential for predation on D. gallinae by several native predatory mites, a spider, a pseudoscorpion and three insects has been reported from in vitro tests (Lesna et al, 2009;Stockton, 2004;Toldi et al, 2017;Zriki et al, 2020). Significant covariations between abundances of three taxa of predatory mites and of D. gallinae suggest that these predators are indeed associated to the pest in henhouses (Roy et al, 2020). Yet, the link between predation processes and the regulating service of D. gallinae in farms could not be demonstrated (Roy et al, 2020), while it exists with one of the above mite taxa (Androlaelaps casalis) in the nests of wild birds (Lesna et al, 2009).…”

“…Significant covariations between abundances of three taxa of predatory mites and of D. gallinae suggest that these predators are indeed associated to the pest in henhouses (Roy et al, 2020). Yet, the link between predation processes and the regulating service of D. gallinae in farms could not be demonstrated (Roy et al, 2020), while it exists with one of the above mite taxa (Androlaelaps casalis) in the nests of wild birds (Lesna et al, 2009). The three predators of D. gallinae proved to be almost ubiquitous in the farms studied, making it impossible to measure their specific effect in henhouses, unlike in the bird nests studied.…”