Effect of honey bees (Apis mellifera) and wild insect pollination on rapeseed (Brassica napus) yield in the Argentine Pampas: Results of a caging experiment

A honeybee on rapeseed

by Scally et al.

Rapeseed (canola) can produce higher yields when its flowers are visited by insects. In the Argentine Pampas, farming is highly intensive and there are few natural areas that support wild pollinators. This makes it especially important to understand how both managed honeybees and wild insects contribute to crop production.

We studied how insect pollination affects rapeseed by comparing three groups of plants: those open to all insects, those visited only by honeybees (Apis mellifera), and those from which all insects were excluded. Plants visited only by honeybees produced 33% more seeds than plants without insect visits. Plants exposed to all insects produced 20% more seeds than plants without insects.

Higher yields were mainly due to plants producing more fruits and more seeds per fruit. Seed quality was also better in pollinated plants, with higher ripeness, germination, and vigor.

Our results show that insect pollination is important for rapeseed production even in highly intensive farming systems. Supporting wild pollinators through appropriate agricultural practices, and using managed honeybees when needed, could help increase crop yields in the Argentine Pampas and other similarly intensified agricultural regions.

 Read the scientific publication in JPE.

 

Pollination success in apples is dependent upon wild bees and orchard design

Apple orchard in Norway

by Vassvik et al.

Apples depend upon pollinators for increased quality and yield. In Norway little is known about which bees visit apple flowers, how bees’ behaviour affects pollination, and how the arrangement of different apple cultivars affects cross-pollination. Therefore, we studied pollination success in 18 apple orchards, in Eastern and Western Norway, containing three different cultivars: Aroma, Discovery, and Summerred. We used insect traps to estimate number of bees and identify the different bee species, and studied bee behaviour through observations in the field.

We found that a higher number of wild bees (bumblebees and solitary bees) increased pollination success, this means that the apples contained more seeds, an important determinant for increased apple quality. However, no effect on pollination success was found for a higher number of honeybees. The bees also mainly flew between neighbouring flowers, and therefore pollination success, due to increased cross-pollination, was higher in integrated orchards (rows of different cultivars are planted close together) compared to block design orchards (single cultivar planted over a larger area).

Our results highlight the importance of promoting for wild bees in apple orchards while also ensuring there is compatible pollen, from different apple cultivars, in the orchards for optimal pollination.

Read the scientific article in JPE.

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Norwegian (bokmål) version

Pollineringssuksess i epler er avhengig av ville bier og eplehagestruktur 

Epler er avhengig av pollinerende insekter for økt kvalitet og avling. I Norge vet vi lite om hvilke bier som besøker epleblomster, hvordan bienes atferd påvirker pollinering, og hvordan plasseringen av kompatible eplesorter påvirker krysspollinering. For å studere dette nærmere undersøkte vi pollineringssuksess i 18 eplehager, i Øst- og Vest-Norge, bestående av tre ulike eplesorter: Aroma, Discovery og Summerred. Antall bier og hvilke arter av bier som var til stede i eplehagene ble kartlagt ved hjelp av insektsfeller, og bienes atferd ble registrert gjennom observasjoner i felt.

Vi fant at økt forekomst av ville bier (humler og solitære bier) økte pollineringssuksessen, som betyr at eplene inneholdt flere frø, noe som er viktig for økt kvalitet på eplene. Økt forekomst av honningbier hadde derimot ingen effekt på pollineringssuksessen. Biene fløy også hovedsakelig mellom nærliggende blomster, og pollineringssuksessen, på grunn av økt krysspollinering, var derfor høyere i integrerte eplehager (hvor rader av ulike eplesorter er plantet nær hverandre) sammenlignet med eplehager med blokkstruktur (hvor en eplesort er plantet over et større område).

Resultatene våre understreker viktigheten av å fremme ville bier i eplehager, samtidig som man sikrer tilgang på kompatibelt pollen, fra ulike eplesorter, for optimal pollinering.