Sanitary measures considerably improve the management of resistant Norway rats on livestock farms.

BACKGROUND: Norway rats (Rattus norvegicus) need to be controlled to prevent transmission of pathogens and damages to stored products and material, leading to considerable economic risks and losses. Given increasing resistance in Norway rats, the most persistent, bio-accumulative and toxic anticoagulant rodenticides are widely used for management, which presents hazards to the environment especially for non-target species. We investigated how sanitary measures improved management of Norway rats on 12 paired livestock farms in a region of Germany with a high population of resistant rats for reducing application of rodenticides. We recorded food intake, and tracked activity and resistance frequency during the pre-treatment, treatment and post-treatment periods. RESULTS: In the post-treatment period, farms using sanitary measures had a higher control success with > 13% more bait boxes without feeding than farms not using sanitary measures. In addition, the reoccurrence of rats was delayed by 85 days. With increasing accessibility to buildings and more precise positioning of the boxes, control success improved, especially when rats could not spread from water-bearing ditches through the sewer system, and when rat-hunting animals were present. Resistant animals were more common indoors than outdoors, and there were more resistant rats recorded before and during treatment than in the post-treatment period. CONCLUSION: The control success was substantially higher and reoccurrence was delayed using sanitary measures on farms. Sanitary measures can reduce resistance indirectly due to delayed re-colonization and establishment of resistant populations inside buildings. Hence, sanitary measures help to reduce economic losses, rodenticides required for rat management and environmental risk especially in the resistance area. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Like or dislike: Response of rodents to the odor of plant secondary metabolites.

Rodents, including common voles (Microtus arvalis) and house mice (Mus musculus) cause immense pre-harvest and post-harvest losses. Therefore, developing methods that mitigate these losses while maintaining their role in ecosystems is a priority. Several plant secondary metabolites (PSM) which significantly reduce food intake of both species under laboratory conditions have been identified. However, before these can be used in rodent pest management, they must be tested under more natural conditions where other food sources are available. In this study, the odors of 4 PSMs were evaluated for their repellent effects in experiments conducted in semi-natural enclosures. Soil treated with PSMs or untreated soil (experimental control) was placed in an underground box containing food (rolled oats). We quantified the number of visits to each box and could demonstrate that all 4 PSMs reduced the number of visits to treatment boxes in both rodent species. For common voles the combination of methyl nonyl ketone + black pepper oil was the most repellent PSM. House mice made fewer visits to all PSM boxes; boxes with the anthraquinone were visited least. Furthermore, house mice consumed less food from boxes containing soil treated with all 4 PSMs. Our results suggest that PSMs are repellent in murid and microtine rodents under semi-field conditions. In addition, the future use of PSM odors for repelling both pest species, especially house mice, seems promising. Further investigations with other PSMs, different concentrations as well as alternative application methods are needed to repel common voles from attractive crops.

Plant Secondary Metabolites as Rodent Repellents: a Systematic Review.

The vast number of plant secondary metabolites (PSMs) produced by higher plants has generated many efforts to exploit their potential for pest control. We performed a systematic literature search to retrieve relevant publications, and we evaluated these according to PSM groups to derive information about the potential for developing plant-derived rodent repellents. We screened a total of 54 publications where different compounds or plants were tested regarding rodent behavior/metabolism. In the search for widely applicable products, we recommend multi-species systematic screening of PSMs, especially from the essential oil and terpenoid group, as laboratory experiments have uniformly shown the strongest effects across species. Other groups of compounds might be more suitable for the management of species-specific or sex-specific issues, as the effects of some compounds on particular rodent target species or sex might not be present in non-target species or in both sexes. Although plant metabolites have potential as a tool for ecologically-based rodent management, this review demonstrates inconsistent success across laboratory, enclosure, and field studies, which ultimately has lead to a small number of currently registered PSM-based rodent repellents.