Wild bee abundance and pollination service in cultivated pumpkins: farm management, nesting behaviour and landscape effects

  • Published source details Julier H.E. & Roulston T. H. (2009) Wild bee abundance and pollination service in cultivated pumpkins: farm management, nesting behaviour and landscape effects. Journal of Economic Entomology, 102, 563-573.


Tillage (ploughing/cultivation) and irrigation may affect ground-nesting bee species, such as the common Eastern bumblebee Bombus impatiens and the squash bee Peponapis pruinosa (which collects pollen only from the family Cucurbitaceae, including pumpkins Cucurbita pepo). This study examined the effects of no-tillage and irrigation on wild bee abundance on pumpkin farms in northern Virginia and Maryland, eastern USA.

Twenty farms were selected, each with at least 0.4 ha of pumpkin, grown for at least one year before the study. Ten farms had tilled the previous year’s pumpkin patch to an average depth of 25 (± 5.5 cm) cm in autumn or spring. Nine of these had also tilled a new pumpkin patch, usually in a different location. These were paired with 10 farms (2.3 – 17.6 km away) with similar histories of pumpkin cultivation and similar levels of insecticide use but which had not tilled the previous year’s pumpkin patch, leaving it undisturbed or planting a no-tillage crop.
Bees visiting pumpkin flowers were identified and counted between 8:00 and 10:00 h in mid-July and again in August 2006, on five 50 m transects of pumpkin field at each study farm.
Six farms were irrigated, five with overhead irrigation, one with drip irrigation.

There was no significant difference in the number of squash bees or bumblebees between farms that tilled after the pumpkin crop and those that did not. However, the pumpkin crop flowers later than other cucurbits and the authors suggest a tillage effect on squash beesmay have been masked by bees dispersing early in the season to find forage elsewhere.

Irrigation increased the number of bees, perhaps by making the soil softer. Irrigated farms had significantly more squash bees than paired non-irrigated farms (average of 27.2 bees recorded at irrigated farms and 9.0 bees at non-irrigated farms).

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at:


Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 19

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust