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Dehusking of seed by small mammals - default values for use in risk assessment. - PS2349

In the current revision of the EFSA Birds and Mammals Guidance Document dehusking is highlighted as a possible route of decreasing the risk of injury to small mammals from pesticide exposure. EU Directive 94/414 requires that plant protection products have no unacceptable effects on the environment particularly non-target species. Defra Pesticides Safety Directorate (PSD) is responsible for assessing the environmental safety of pesticides in the UK.

The indicator species usually identified in risk assessment for granivorous small mammals is the woodmouse (Apodemus sylvaticus) but other species such as the bank vole may find hoarded seed and thus be exposed. Although bank voles are not obligate seed eaters they have been observed to consume up to 3g of wheat seed in the absence of other food with no deprivation period (CSL unpublished data). In times of food shortages voles may find seed hoarded by woodmice and thus be exposed. It is unclear what range of seed types they may readily consume and whether they exhibit dehusking.

This proposal aims to generate more robust generic data for use in risk assessment for a range of 5 seed types commonly used in the UK (e.g. wheat, maize, barley, pelleted sugar beet, peas). It is intended to base this on the worst case exposure scenario, i.e. deprivation period followed by no-choice exposure to treated seed. To confirm that these data are also protective of other species, i.e. bank vole, which may access hoarded seed a more limited study would be undertaken to identify any significant differences consumption of seed types and dehusking. This would allow the risk posed to bank voles encountering hoards of treated seed to be assessed.

The output would be a report detailing the key aspects of the design of such a study and level of consumption and dehusking that occurs for the two species for a range of commonly drilled seed types. This would allow PSD to provide information to registrants on the generic data used and to provide guidance on the design of any study to identify whether the palatability of the seed coating was significantly affected by the formulation under discussion.
1) Determine dehusking behaviour for a range of test conditions (food restriction/deprivation) (31.10.08)

2) Determine suitable methods to measure the scale of dehusking. (31.01.09)

3) Establish that wood mice exposed to a range of seed types (pelleted sugar beet, barley, wheat, maize, pelleted oilseed rape, beans and peas) will exhibit some form of, partial or full, dehusking. (31.05.09).

4) Determine the similarities and differences to wood mice by measuring the behavioural responses of another small mammal to a range of seed types. (31.08.09)

5) Produce a final report with all results, implications for risk assessment and recommendations for further work. (30.09.09)

Project Documents
• Final Report : Dehusking of seed by small mammals - default values for use in risk assessment   (686k)
Time-Scale and Cost
From: 2008

To: 2009

Cost: £55,920
Contractor / Funded Organisations
Central Science Laboratory
Behaviour change              
Biological Effects              
Environmental Effects              
Environmental Impact              
Environmental Protection              
Habitat conservation              
Pest and Weed Control              
Pesticide use              
Plants and Animals              
Risk assessment and management              
Fields of Study
Pesticide Safety