Late flowering time enhances insect pollination of turnip rape

Abstract

1. Ecological intensification has been proposed as a strategy to mitigate the impacts of conventional intensive land use on pollinators and insect pollination. However, research has concentrated on the effects of land management on pollinator abundance and diversity, while studies directly measuring pollination services are still lacking for many crops and regions.2. This study examines the effects of landscape heterogeneity, pesticide use intensity and flowering time on insect pollination of turnip rape Brassica rapa ssp. oleifera, a major oil crop at high latitudes. The field experiment included monitoring pollinator visits on turnip rape flowers and measuring yield in 34 spring-sown turnip rape fields in Southern Finland. The fields were situated in two landscape types that differed in the cover of arable land and represented independent gradients of pesticide use intensity and flowering time. 3. Based on flower visits and number of seeds per silique, turnip rape was best pollinated in fields with late flowering time. The result suggests a temporal mismatch between crop flowering and the availability of pollination service in early sown fields. The increase in flower visits during summer was steeper among fields with low than high pesticide use, possibly due to a faster colony growth of important bee pollinators.4. Pollinator community in turnip rape fields was more diverse in heterogeneous landscapes with less arable land than in homogeneous field-dominated landscapes, suggesting higher stability of pollination services in diverse landscapes. Total yield per plant was positively related to pesticide use intensity. The relation-ship between insect pollination and total yield was weakened by high compensation capacity of turnip rape, the plants producing more flowers under poor pollination.6. Synthesis and applications. Crop pollination can be enhanced by shifting sowing time to better match crop flowering to the peak availability of the most important pollinators. Reduced pesticide use may also enhance pollination services but can lead to the total yield reduction due to pests. This highlights the need for pollinator-friendly pest control methods to maintain turnip rape yields while conserving pollination services. K E Y W O R D S bees, ecological intensification, flower visitation, landscape heterogeneity, pesticide use, pollinators, syrphid flies, turnip rape | 1165 Journal of Applied Ecology TOIVONEN ET al.

Linking pollinator occurrence in field margins to pollinator visitation to a mass-flowering crop

“…However, observational squares are more practical in monitoring pollinator visitation to crop flowers, and they also allow linking pollinator visits to crop yield. The effects of pollinator visits on turnip rape yield in the same study system were reported by Toivonen et al (2019): The number of seeds per silique increased with increasing number of flower visits, indicating enhanced crop pollination, whereas species richness of pollinators had no yield effect.…”

Pesticide residues in honeybee-collected pollen: does the EU regulation protect honeybees from pesticides?

“…oleifera) and turnip rape (Brassica rapa subsp. oleifera) are examples of crops that strongly attract honeybees and wild bees but also suffer from harmful pests such as common pollen beetle (Brassicogethes aeneus) that may destroy the entire yield if not controlled (e.g., Toivonen et al 2019;Lindstöm et al, 2017). Commonly used insecticides in the cultivation of oilseed brassicas include pyrethroids taufluvalinate, esfenvalerate, and lambda-cyhalothrin, as well as Responsible Editor: Philippe Garrigues * Lotta Kaila lotta.kaila@helsinki.fi; ext.lotta.kaila@luke.fi Extended author information available on the last page of the article the nenonicotinoid thiacloprid, which all interfere with the insect nerve system (Davies et al 2007;Tomizawa & Casida 2005).…”

Animal pollination increases stability of crop yield across spatial scales

“…Several publications in our analysis were conducted to measure differences in pollination service at different locations by comparing the yield of open‐pollinated plants with control plants enclosed in cages at each location (e.g. Perrot et al, 2018; Toivonen et al, 2019; Zou et al, 2017). Based on previous research (Garibaldi, Steffan‐Dewenter, et al, 2011; Lázaro & Alomar, 2019), we hypothesised that differences (instability) in pollination service between locations would make yield less stable in these open pollination experiments, in comparison to experiments where pollinator activity was maximised by introduction of pollinating insects or hand‐pollination inside cages (e.g.…”