Most wild pollinators work in a 50–2000 m radius around the nest (Kohler et al., 2008) with much smaller radii (150–600 m) identified for foraging trips of 16 solitary bees (Gathmann & Tscharntke, 2002). The lower the foraging radius, the higher the eventual exposure to pesticides, making solitary bees more exposed to pesticides than social bees (Uhl & Brühl, 2019).

Many solitary wasps nest in soil, wild bees nest either in soil (Halictus, Lasioglossum, Andrena, Eucera, Anthophora, Amegilla and Melitta) or in hollow stems or old wood (Xylocopa, Megachile and Osmia). In monocultural areas with large field sizes, field edges become rare (Feltham et al., 2015), and dead wood, hollow stems, and perennial aboveground biomass for nesting are even more scarce, thus disadvantaging cavity‐nesting pollinators (Brown et al., 2020; Everaars, 2012). They live closer to forest patches (Everaars, 2012). Long distances between nests and foraging plants reduce pollination services (Roulston & Goodell, 2011). As such, agriculture depends to a high extent on ground‐nesting pollinators that nest in the entire field area (Everaars, 2012; Sgolastra et al., 2018). Pollinators nesting in the soil of fields face three additional main threats in comparison to honeybees and cavity‐nesting pollinators: tillage, soil compaction by heavy machinery, and chemicals accumulating in soil.

Little is known about the impacts of tillage on the regeneration of solitary ground‐nesting pollinators (Kratschmer et al., 2018). They usually stay in the ground almost a full year, sometimes several years, emerging for some weeks or months to reproduce, pollinate, and lay eggs (Michener, 2007; Willis Chan et al., 2019). Some bees prefer tilled soil to build nests (Skidmore et al., 2019). However, as many ground‐nesting pollinators place their eggs up to 30 cm below surface (Roulston & Goodell, 2011), deep tillage (around 15–30 cm) can bury nests or destroy the tunnel (Hopwood et al., 2021; Roulston & Goodell, 2011). Tillage reduces offspring emergence and delays emergence of surviving offspring of ground‐nesting squash bees (Ullmann et al., 2016). No‐tillage farms hosted three times higher density of squash bees as farms employing tillage (Shuler et al., 2005).

Soil compacted by heavy machinery threatens ground‐nesting pollinators (Potts & Willmer, 2003). As burrowing in compacted soil is hampered even for earthworms (Beylich et al., 2010), heavy machinery might compact soil to an extent that pollinator larvae are smashed or cannot emerge successfully from their natal nests. Compacted soil has reduced macropore volume and thus different O₂ and CO₂ concentrations affecting soil organisms (Beylich et al., 2010). Effects of these different concentrations on hatching offspring and pollinator females digging to lay eggs have not yet been studied. In compacted soil it is possible that fungal diseases may impact non mobile stages (pupae) of ground‐nesting pollinators due to reduced soil water drainage. The impacts of different soil tillage regimes at different times on the reproduction of ground‐nesting pollinators should be assessed to enhance guidelines for less damaging soil cultivation.

Chemicals and neonicotinoid insecticides accumulate in soil, with up to 94% of the chemical load of neonicotinoids found in soil and water (Goulson, 2014). Female solitary ground‐nesting pollinators dig vertical and horizontal tunnels and cells in soil to lay their eggs, some species create deep and multibranched tunnel systems (Willis Chan et al., 2019). However, pesticide risk assessments are mostly conducted on honeybees (Uhl & Brühl, 2019), though honeybees are more mobile than wild pollinators and enjoy substantial support by beekeepers (hives, transport). To a lesser extent, pesticide risk assessments include bumblebees (Hatfield et al., 2021) that occupy existing mouse holes for their nests and cavity‐nesting species like Osmia (Rundlöf et al., 2015). Pesticide risk assessments rarely include the most exposed groups, ground‐nesting pollinators or aquatic syrphids (Anderson & Harmon‐Threatt, 2019; Goulson, 2014; Rundlöf et al., 2015; Sgolastra et al., 2018; Willis Chan et al., 2019; Willis Chan & Raine, 2021). Exposure to imidacloprid reduces the life expectancy of solitary bees (Anderson & Harmon‐Threatt, 2019). Hoary squash bees in Curcubita fields in Ontario exposed to imidacloprid build 85% fewer nests and their next generation is reduced by 89% (Willis Chan & Raine, 2021). The toxicity for larvae has not yet been tested (Willis Chan et al., 2019). Wild bees’ ability to reproduce may be reduced even in the year following exposure to neonicotinoids (Woodcock et al., 2017). Elado (a combination of clothianidin and the non‐systemic pyrethroid β‐cyfluthrin) decreases wild bee density, solitary bee nesting, growth of bumblebee colonies, and reproduction (Rundlöf et al., 2015).

Female solitary ground‐nesting pollinators are exposed to neonicotinoids with their entire bodies while digging. The time of contact exposure might be long, Dasypoda visnaga and Dasypoda maura dig up to 80 cm deep (El Abdouni et al., 2021). The exposure of different ground‐nesting pollinators can differ according to their body size, the size of nests, the month of nest‐building activities, preferred crops, farming practice, and precipitation, which may reduce the concentration of chemicals in soil. Research is needed on the interaction of different chemicals with each other in soils and how unintended side effects affect the total toxicity for ground‐nesting pollinators. This is even more urgent with respect to climate change not only, but notably in dry regions like North Africa, Near and Middle East, and Asia (pests are not washed away by rain, they expand regionally, regenerate faster, and drought‐stressed plants attract more pests) (Deutsch et al., 2018; Skendžić et al., 2021). Farmers can increase the diversity of pesticides used, their concentration, and the frequency of application. Also, the concentration in soil can increase due to higher evaporation. Research is needed on the duration of contact exposure of different female ground‐nesting pollinators in soil and how this impacts their health (Willis Chan & Raine, 2021).

The urgent need to protect ground‐nesting pollinators below ground using soil‐protection strategies is obvious. As pesticides and particularly neonicotinoids affect other species of soil biodiversity like earthworms (Pisa et al., 2014), ants (Schläppi et al., 2020) and even aboveground species like birds (Goulson, 2014) and bats (Hsiao et al., 2016), stronger collaboration of scientists and policymakers can be advantageous.