Weeds in the treated field – a realistic scenario for pollinator risk assessment?

In July 2013 the European Food Safety Authority (EFSA) released its final guidance on the risk
assessment of plant protection products (PPPs) to bees. One objective of the guidance was to
produce a simple and cost effective first tier risk assessment scheme to ensure that the
appropriate level of protection is achieved. However, recent impact analyses have indicated that
the first tier of this risk assessment does not act effectively as a screen for compounds of low risk to
bees. For example substances showing no toxicity to bees often fail the tier 1 risk assessment
based on a worst-case exposure to flowering weeds inside the treated field. If realistic farming
practices (e.g. tillage and herbicide applications) are considered, weeds are not usually prevalent
in arable fields. It is therefore suggested that the scenarios in the guidance could be considered
overly conservative and in some instances unrealistic. The EFSA guidance states that if <10% of the
area of use is flowering weeds then the exposure route is not relevant in the 90th %ile case, and
thus does not need to be considered. However, despite this, the option to generate data or refine
assessments based on available data is questioned as no guidance for the assessment of the
abundance of weeds is available. As part of an industry-led initiative we present and discuss the
use of empirical evidence (i.e. occurrence and growth stage of weeds in control plots from
herbicide efficacy field trials conducted for regulatory submission) to illustrate that the scenarios
in the guidance document could be modified using currently available data to create a more
effective tier 1 risk assessment and still ensure that the appropriate level of protection is achieved.
We have demonstrated here that less than 2% of all weeds recorded in arable crop trials
(represented here by wheat, oilseed rape, sugar beet, sunflower, potatoes, maize, peas and beans)
are at a flowering growth stage; therefore in arable crops the flowering weeds scenario is not
applicable for the 90th %ile exposure. For permanent crop trials (represented here by orchards and
vines) 37% of weeds were recorded at a flowering growth stage. When the attractiveness and
density data are considered, the percentage of attractive, flowering weeds which cover >10% of
the ground area is only 12.3%, indicating that for permanent crops further investigation may be
required as to whether this scenario is relevant.