Controlling Voles Using Mechanical Traps
Characterization of the technique
Description of the technique:
Information originally from the Guide for the design of fruit production systems economical in phytopharmaceutical products (2014) / Technical sheet no. 19. For more information see link
Principle
Physical control method consisting of placing mechanical traps in orchards to reduce vole populations. This technique represents a main and effective lever against various vole species: vole terrestrial (Arvicola terrestris ), field vole (Microtus arvalis ), Mediterranean vole (Microtus duodecimcostatus ), pine vole (Microtus subterraneus ). However, mechanical trapping is quite demanding and very time-consuming.
Implementation means and conditions for the technique's effectiveness
To implement this practice and ensure maximum effectiveness, it is important to identify signs of vole activity (burrows, holes, scratching, mounds) to locate galleries. Traps should be placed as soon as the first signs of rodent activity are detected, regardless of the time of year. However, trapping is more effective during the breeding period (spring-autumn depending on species). Monitoring during the population growth phase within the framework of the interannual population cycle remains a key element to increase the effectiveness of this technique.
The technique:
Two types of trapping are distinguished: "curative" trapping implemented to try to control existing populations and "maintenance" trapping when the trapper has cleaned the plot and traps at localized hotspots to limit reinfestation.
At the same time, two control systems exist:
1) Active control using lethal traps that kill voles directly. In this case, it is possible to use:
- either guillotine traps (e.g. Top-Cat®), currently the most practical and widely used. Their implementation is demanding when a large number must be placed on a plot and requires a lot of time. The method becomes very costly over large areas (cf number of traps needed).
- or pinch traps (e.g. Putange®), lightweight to carry but more demanding to set and check during intensive use (galleries must be opened).
Guillotine or pinch traps are placed in the movement galleries, avoiding exit galleries leading to mounds (vole Mediterranean). The trapper has a certain number of traps (minimum 5 to 10) and "rotates" through the plot, zone by zone, emptying and resetting the traps: it is important to check them regularly, a trap that has caught or been triggered is no longer operational.
2) Passive control using non-lethal traps that do not kill voles directly. These are called funnel traps consisting of a tube or box with a one-way door system. These traps (e.g. Standby®, Scherman®, Longworth®, Ugglan® traps...) were designed to catch live animals to estimate their population on a plot. They are placed on the ground, along an obstacle (often a physical barrier on the plot perimeter) and offset by a few centimeters (about 10 cm). This type of trap is widely used in experiments or research work.
Some funnel traps called release traps have a mechanism (opening roof) that allows predators such as ermine and weasel to escape. Also, after some time of barrier operation, predators (notably red foxes) come to feed directly in the traps by lifting the lid.
Details on the technique:
- To effectively control voles, it is necessary to intervene before the orchard population becomes too large, especially in young orchards.
- It is recommended to put a piece of apple in the trap as an attractant; furthermore, the gallery should be well closed around the trap (no light), which can be achieved by placing a collar dish around the trap.
- It is also important to engage in collective control (organized under the aegis of a sanitary organization (OVS) for the plant domain such as the Regional Federation of groups for defense against harmful organisms - Fredon) and in combination with other control methods to limit reinfestations especially if there are grasslands around the plot.
- This technique causes constraints for agricultural machinery passage (marking traps) and for soil maintenance (weed management in particular).
- Traps must be moved according to active mounds or when the animal has detected the trap and systematically triggers it without being caught.
- The field vole does not create mounds like other species. However, it creates small mounds somewhat flattened on their top, harder to spot.
- Moreover, it is important to follow training on trapping to learn how to handle traps and to know target and non-target species.
Implementation period
On established crops
Spatial scale of implementation
Plot
Application of the technique to...
All crops:
Easily generalizable
The technique can be applied in arboriculture but also in large crops and vegetable production.
All soil types:
Not applicable
All climatic contexts:
Not applicable
"Environmental" criteria
Other:
No effect (neutral) No knowledge on the impact of mechanical trapping on all environmental indicators.
To control voles, whether by chemical or mechanical techniques, movements within a plot are done on foot. Only the number of passes per plot differs between chemical and mechanical control. In a global approach, one can suspect that the manufacture of rodenticide and its transport on the farm have an energy cost. However, no precise knowledge is available to date.
The only known and concerning impact is related to rodenticide toxicity with negative effects on food chains and predator mortality.
"Agronomic" criteria
Productivity:
Variable. This technique helps limit mortality of young trees in particular. Therefore, it can be estimated that it improves productivity / ha. It is an alternative technique whose effectiveness is clearly conditioned by the implementation of several complementary solutions.
Production quality:
No effect (neutral)
Soil fertility:
No effect (neutral)
Water stress:
No effect (neutral)
Functional biodiversity:
Increasing. It is important to emphasize that chemical control presents significant risks for the food chain and domestic animals by ingestion of poisoned animals and to a lesser extent by consumption of poisoned baits. It is to be avoided in case of high vole inoculum (prohibition threshold).
The impact on functional biodiversity is therefore positive by limiting the risk of poisoning by rodenticides in the food chain (this is one of the reasons that led to drafting the vole decree). Moreover, release traps favor the presence of predators around the plot (fox, cat, ermine, etc.) that consume voles in the traps.
Mechanical traps are harmless to the environment and humans. Only a moderate risk exists for weasels or ermines that can move in galleries and in Standby® type traps.
"Economic" criteria
Operational costs:
Increasing. Spring mechanism traps have a lifespan of several years. However, labor costs increase operational costs because the technique requires a lot of time for frequent monitoring (more than 200 h/ha depending on initial population level).
Price of pinch traps: €2-3 incl. tax (unit)
Price of guillotine traps: about €40-50 incl. tax (unit)
Mechanization costs:
No effect (neutral)
Margin:
No knowledge on impact
"Social" criteria
Working time:
No effect (neutral). Chemical control against voles as well as mechanical trapping system is done by hand. However, the latter requires more working time than control with rodenticide.
Peak period:
Variable. This technique requires a short training time (detecting activity signs, handling traps, trapping management strategy), frequent visual checks, and time to set traps.
Variable time depending on pressure, equivalent to several days per year, interventions on at least two periods of the year. Moreover, monitoring may need to be done during harvest periods for the Mediterranean vole, which increases workload during this peak activity.
Trapping time will depend on several aspects:
- trapping pressure,
- number and type of traps,
- vole density,
- presence of moles,
- ground cover (which hides signs),
- importance of natural predation,
- level of reinfestation from individuals refractory to trapping and populations surrounding the orchard.
Observation time:
Increasing. Very time-consuming technique because of the need for regular monitoring (4 to 5 times more time than chemical control). In case of high pressure, trapping becomes too time-consuming to maintain populations at a tolerable threshold.
A strategy to reduce observation time is to train tractor drivers (who pass everywhere) to spot and report the presence of mounds.
For more information
- Alternative control methods against the Mediterranean vole: Tronel C., Bouniol M. CTIFL, Technical brochure, 2013 Infos-Ctifl, 295, 32-35 - link to brochure
Keywords
Bioaggressor control method:
Physical control
Mode of action:
Action on the initial stock
Type of strategy regarding pesticide use:
Substitution
Annexes
S'applique aux cultures suivantes
Favorise les auxiliaires
Défavorise les bioagresseurs suivants
