Exposure – crop factors

Period(s) in the growing season when pesticides are applied to the crop

Determinant for factors below

Period(s) in the year when the crop flowers

If overlap between flowering of crop and pesticide applications 🡺 higher exposure risk 

Period(s) in the year when bees are active foraging or collecting nesting materials

If overlap between bee activity in crop and pesticide applications 🡺 higher exposure risk

Period(s) when weeds are flowering in the crop which may be attractive to wild bees

If overlap between flowering of weeds and pesticide applications 🡺 higher exposure risk

Crop has extrafloral nectaries

If extrafloral nectaries present in crop 🡺 higher exposure risk

Crop is regularly infested with honeydew producing insects

If honeydew producing insects present in crop 🡺 higher exposure risk

Exposure – bee biology factors

Location of nest in relation  to crop field

In-field and field-border nests 🡺 higher exposure risk

Off-field nests 🡺 lower exposure risk (depending on distance)

Bee foraging range

If in-field and field border nests: shorter foraging range 🡺 higher exposure risk

If off-field nests 🡺 no clear correlation with risk

Time spent foraging, or collecting nesting materials, per day (“time-out-of-nest/hive”)

More hours out-of-nest/hive 🡺 higher exposure risk

Number of days spent foraging on the crop

More days spent foraging 🡺 higher exposure risk

Number of different nectar and pollen plant species used during crop flowering

Fewer species 🡺 higher exposure risk

Collective pollen and/or honey storage in the nest (social bees)

If collective pollen and honey storage 🡺 lower exposure risk due to mixing and microbial action

Exposure & impact – pesticide use/application practices

Formulation type

Some formulations types (e.g. micro-encapsulation, sugary baits, DP, WP) 🡺 higher exposure risk

Mode of application

Some modes of application (e.g. dusting, aerial application, drilling treated seed that produces dust) 🡺 higher exposure risk

Some modes of application (e.g. seed/soil treatment with non-systemic pesticide; brushing) 🡺 lower exposure risk (unless soil nesting bees)

Application rate

For the same pesticide product: higher application rate 🡺 higher exposure/impact risk

Application frequency

Higher application frequency 🡺 higher exposure risk

Application interval

Shorter interval between applications 🡺 higher exposure risk

Impact & recovery – pesticide properties

Contact LD50 (adult)

Lower LD50 🡺 higher impact (for similar exposure levels)

Oral LD50 (adult)

Lower LD50 🡺 higher impact (for similar exposure levels)

Oral LD50 (brood)

Lower LD50 🡺 higher impact (for similar exposure levels)

Foliar residual toxicity

Higher residual toxicity🡺 higher impact (for similar exposure levels) & 🡺lower likelihood of recovery after pesticide impact

Impact & recovery – life history and population dynamics factors  1

Degree of sociality

High degree of sociality with one or more reproductive queens and separate foragers 🡺 lower risk of impact to the population/colony because pesticide affect primarily foragers (except for IGRs)

Fraction of population/colony active out of the nest/hive (social bees)

Higher fraction of population of colony active out of the nest/hive 🡺 higher risk of impact for the whole population/ colony

Number of offspring per queen/reproductive female

Greater number of offspring 🡺 greater likelihood of population recovery after pesticide impact

Number of generations per year

Greater number of generations per year 🡺 greater likelihood of population recovery after pesticide impact

Migration and dispersal distance

Greater dispersal distance 🡺 greater likelihood of population recovery after pesticide impact (if cropping is patchy); however if migratory routes are used, possible multiple exposure to pesticide