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Common voles (Microtus arvalis) are widespread in the European agricultural landscape from central Spain to central Russia. During population outbreaks, significant damage to a variety of crops is caused and the risk of pathogen transmission from voles to people increases. In 2019, increasing or unusually high common vole densities have been reported from several European countries. This is highly important in terms of food production and public health. Therefore, authorities, extension services and farmers need to be aware of the rapid and widespread increase in common voles and take appropriate measures as soon as possible. Management options include chemical and non-chemical methods. However, the latter are suitable only for small and valuable crops and it is recommended to increase efforts to predict common voles outbreaks and to develop and field test new and optimized management tools. [ABSTRACT FROM AUTHOR]

Common voles (Microtus arvalis) can cause severe crop damage in European agriculture and are usually managed with rodenticides. Population dynamics and behavioral studies question rodenticide effectiveness, and an ecologically based management is needed. A useful addition to such a toolbox could be repelling odor barriers along field margins minimizing migration of voles to crops. We screened 17 plant products and mammalian scents in T-maze trials to test their repelling effects. The most repelling compounds (carrot seed oil (CS), black pepper oil (BP), spruce needle oil (SN), benzaldehyde (BA), BA and BP in double concentration (dc), combinations of BP + BA and BP + CS) were tested further in enclosures. We measured in four populations how often voles crossed enclosure compartments through channels treated with a compound or without a compound. In addition, the amount of rolled oats eaten by voles near treated and untreated channels was compared. In enclosures, voles avoided significantly channels treated with BP (79% more crossings through the control channel) and BP (dc) (42%). Voles consumed significantly more rolled oats near control channels than in the presence of BP + CS (72% more feeding at control), CS (51%), BA (dc) (36%), BP (32%) and BA + BP (28%). This demonstrated for the first time that natural compounds can reduce uptake of a highly attractive food source in common voles under semi-natural conditions. BP + CS was the most successful feeding deterrent and has the potential to be included in an ecologically based management approach. [ABSTRACT FROM AUTHOR]

Second-generation anticoagulant rodenticides potentially build persistent residues in animals and accordingly pose a risk of secondary poisoning. We examined the effect of a low concentration of cholecalciferol in brodifacoum bait on bait consumption by Norway rats (Rattus norvegicus Berkenhout 1769) and on the control success in a laboratory study and in field trials. Additionally, the efficacy of both baits was determined against resistant Y139C rats. Cholecalciferol caused a strong stop-feed effect after two days in the laboratory study. On two field study sites each, bait containing either 25 mg kg−1 brodifacoum or 25 mg kg−1 brodifacoum and 100 mg kg−1 cholecalciferol was applied to treat infestations of Norway rats. Infestations were assessed pre- and post-treatment. Rats were radio-tagged, and carcasses were searched for during the treatment period. DNA of each rat was genotyped to determine the resistance status conferred by the VKORC1 gene. On all farms, control success exceeded 90%. On farms treated with brodifacoum only, the ratio of total bait consumption to pre-treatment census was significantly higher (6.6 and 4.8 times) than on farms treated with the combination (2.7 and 2.9 times). 78.8% of 183 rats were confirmed Y139C resistant. Bait ingestion was reduced by almost fifty per-cent when cholecalciferol was added to the bait with no impact on control success. All treatments resulted in control levels exceeding 90%, despite a high proportion of anticoagulant-resistant rats. When the use of highly toxic compounds is required in resistance management, addition of cholecalciferol to these baits may reduce the transfer of residues to the environment. [ABSTRACT FROM AUTHOR]

Rodents are among the most damaging pests in agriculture worldwide. High-density populations of rodent pests can kill plants or diminish their growth, and reduce both fruit size and the number of seeds. Therefore, rodent pests can lead to considerable crop loss and require management actions to minimize damage. Optimal management of pest rodents is usually based on the combination of methods to reduce damage. Although rodenticides are usually the most commonly deployed approach, they have undesirable side effects. Consequently, more environmentally benign approaches such as repellents or attractants to lure rodents away from fields are gaining traction. The dispersal of a large number of juvenile males at certain times of year has prompted us to focus on male rodents for our experiments. We used laboratory feeding experiments to measure how the odor of plant secondary metabolites (PSMs) affects two pest rodents: common voles ( Microtus arvalis, Pallas) and house mice ( Mus musculus, L.). We tested eighteen different PSMs or combinations thereof with voles. Four PSMs reduced feeding and seven PSMs increased feeding of male common voles. Five of six tested odors were effective as repellents against house mice. However, we assume a species-specific response to volatile PSMs repellents. This study demonstrated that four repellents reduced feeding in both rodent species. Our results contribute to the development of non-lethal management tools for rodent pest species that are potentially more suitable than traps and rodenticides. This approach could be applicable to a variety of crops if effective at field conditions. [ABSTRACT FROM AUTHOR]