A fast and reliable larval sampling method for improving the monitoring of fruit flies in soft and stone fruits.

The spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), threatens both the soft-skinned and stone fruit industry in Asia, Europe, and America. Integrated pest management requires monitoring for infestation rates in real time. Although baited traps for adult D. suzukii are widely used for field monitoring, trap captures are weakly correlated to larval infestation rates. Thus, monitoring for larvae instead of adult flies represents the most reliable monitoring technique. Current methods for larval monitoring (e.g., sugar or salt floatation) are time-consuming and labor-intensive. In this study, we develop a new "sleeve method" for detecting larvae in strawberries through the inspection of individual fruits crushed within transparent plastic sleeves. Samples can be optionally frozen until further processing. Based on count data from non-expert observers, the estimation of larval infestation with the sleeve method is fast, precise, and highly repeatable within and among observers. Mean processing time is half the time compared to previous methods (33-80 s per sample depending on infestation levels). As the accuracy of the sleeve method decreases with infestation levels, we suggest ways to improve its accuracy by incubating fruits for 48 h and calibrating data using fruits with a known number of larvae. The method could also be used in other fruits, as it is easier to use, faster, and requires less equipment than previous monitoring methods. Finally, the method represents a promising tool for growers or researchers to effectively monitor and manage D. suzukii and other insect pests of soft and stone fruits.

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

Stimulating the regulation of pests by their natural enemies is a way to improve the sustainability of agriculture and respect for the environment. However, the presence of natural enemies does not guarantee the existence of a pest control service. To what extent are predatory mites commonly found in henhouses actually able to regulate a major egg industry pest mite, Dermanyssus gallinae? To answer this question, we have experimentally recreated portions of a poultry house ecosystem allowing the development of the pest over several generations in the presence of a chick and detritivorous mites (Astigmata) that are ubiquitous and abundant in layer farms. In these conditions, we compared the growth of D. gallinae populations in the presence and absence of native predatory arthropods. No effect of native predators on the growth of the D. gallinae population could be detected despite high initial predator-to-prey ratios and satisfactory growth of predator populations. Prey switching to the alternative prey Astigmata likely dilutes the effect of predation on the target prey. Further exploration is needed to see whether action could be taken to enhance the effect of top-down regulation.

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

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.

Predation interactions among henhouse-dwelling arthropods, with a focus on the poultry red mite Dermanyssus gallinae.

BACKGROUND: Analysis of the poorly explored food webs of henhouse-dwelling arthropods would improve biological control against the poultry red mite (PRM) Dermanyssus gallinae (De Geer). This study aimed to identify trophic links among native predatory arthropods, PRM, and alternative preys. In vitro predation tests were carried out to assess (i) the ability of native predators to feed on PRM juvenile and adult stages in two physiological statuses (unfed and freshly blood-fed) in the absence of any physical barrier, (ii) predator preferences between PRM and astigmatic mites, and (iii) predation interactions between PRM predators. RESULTS: Ten arthropod taxa fed on PRM with predation rates ranging from 4% to 95% in our experimental conditions. They belonged to (i) Acari: Androlaelaps casalis (Berlese), Cheyletus spp., Macrocheles muscaedomesticae (Scopoli), M. penicilliger (Berlese), Parasitus fimetorum (Berlese), Dendrolaelaps spp. and Uroobovella fimicola (Berlese); (ii) other Arachnida: Lamprochernes nodosus (Schrank) (Pseudoscorpionida) and a linyphiid spider; and (iii) Insecta: Lyctocoris campestris (Fabricius). These predators varied in their preference for PRM stages and physiological statuses (unfed or freshly blood-fed). When given a choice, most predators preferred to feed on PRM than astigmatic mites. Bidirectional predation occurred within two pairs of PRM predators (M. penicilliger-Lamprochernes nodosus and A. casalis-Cheyletus spp.), and M. penicilliger had a 100% predation rate on A. casalis. CONCLUSION: Our study highlights the potential of various arthropod predators occurring naturally in poultry houses for conservation and augmentative biological control of PRM. Predation interactions between these predators should be accounted for before developing biocontrol agents against PRM. © 2020 Society of Chemical Industry.