18.104.22.168. Evaluation of the results of the semi-field test
The influence of the test product can be evaluated by comparing the results in the test chemical treatment to the water-treated control and to the reference chemical treatment, and furthermore by comparing the pre- and post-application data regarding:
1) Mortality (dead adult bees, pupae and larvae) within the crop area (linen sheets) and in the dead bee traps (per day and over time after application during bee exposure).It is of interest if an increase in the number of dead pupae is noticed or if malformations of the dead pupae or young dead bees are observed. In case of fenoxycarb in the reference treatment group, an increase in the number of dead pupae can be observed 10-12 days after application. This factor should be considered when demonstrating its sensitivity to bees.
2) Flight intensity in the crop (mean number of forager bees/m² flowering P. tanacetifolia after application)
3) Behaviour of the bees on the crop and around the hive
4) Condition of the colonies (strength (number of bees) of the colonies, presence of a healthy queen, mean values of the different brood stages per colony and assessment date, per Delaplane et al., 2013b)
5) Development of the bee brood (brood indices) in > 100 cells:
The brood-index is an indicator of bee brood development and facilitates comparison between different treatments. It is calculated for each assessment day and colony. For all cells containing the expected brood stage at the respective day, the assessed value (1-5) could be used. For all cells that do not contain the expected brood stage, 0 is used for calculation. All values per hive and assessment day are summed and divided by the number of observed cells in order to obtain the average brood-index.
The compensation-index is an indicator for recovery of the colony. It is calculated for each assessment day and colony. The values of all individual cells in each treatment, assessed at the respective day for each hive, could be summed and divided by the number of observed cells in order to obtain the average compensation-index. By that, the compensation of bee brood losses is included in the calculation.
- Brood termination rate:
Percentage of marked cells where a break (i.e. no successful development) of the bee brood development is recorded, i.e. the bee brood did not reach the expected brood stage at one of the assessment days or food was stored in the cell during BFD +5 to +15.
Specific statistical analysis for bee trials in semi-field and field conditions are still under development. In general, it is recommended to follow the OECD guidelines (OECD, 2006) and Becker et al., 2011.