Bee pollination improves crop quality, shelf life and commercial value

Abstract

Pollination improves the yield of most crop species and contributes to one-third of global crop production, but comprehensive benefits including crop quality are still unknown. Hence, pollination is underestimated by international policies, which is particularly alarming in times of agricultural intensification and diminishing pollination services. In this study, exclusion experiments with strawberries showed bee pollination to improve fruit quality, quantity and market value compared with wind and self-pollination. Bee-pollinated fruits were heavier, had less malformations and reached higher commercial grades. They had increased redness and reduced sugar-acid-ratios and were firmer, thus improving the commercially important shelf life. Longer shelf life reduced fruit loss by at least 11%. This is accounting for 0.32 billion US$ of the 1.44 billion US$ provided by bee pollination to the total value of 2.90 billion US$ made with strawberry selling in the European Union 2009. The fruit quality and yield effects are driven by the pollination-mediated production of hormonal growth regulators, which occur in several pollination-dependent crops. Thus, our comprehensive findings should be transferable to a wide range of crops and demonstrate bee pollination to be a hitherto underestimated but vital and economically important determinant of fruit quality.

Keywords: commercial grades; crop yield; ecosystem services; post-harvest quality; shelf life; strawberry.

Figure 1.

Bee pollination improved the commercial value of strawberry fruits across all varieties as a result of improved commercial grades and higher fruit weight. (a) Commercial values for each fruit were calculated in US$, by multiplying fruit weight with the prevailing market value [29], which was assessed due to harvest time and commercial grades. It was extrapolated to 1000 fruits for a better relationship to market situations. (b) Commercial grades. Fruit proportions (values within bubbles) were calculated for each commercial grade in dependence on pollination treatments (see the electronic supplementary material, S2 for division into varieties). G1/E, commercial grade one/extra; G2, commercial grade two; NM, non-marketable. (c) Weight of strawberry fruits. (a,c) Displayed values were extracted from model estimates and back transformed. Grey points display values of varieties (see abbreviations below), red points display the main effect. Lines are shown for better visualization of related points. Solid red lines for the main effect indicated that pollination treatments were stronger than differences between varieties and thus had a main effect across all varieties (see table 2 for AICc and likelihood values). Abbreviations in alphabetical order: D, Darselect; E, Elsanta; F, Florence; main, main effect; H, Honeoye; K, Korona; L, Lambada; Sa, Salsa; Sy, Symphony; Y, Yamaska.

Figure 2.

Bee pollination improves the post-harvest quality of strawberries. (a) Shelf life in days until 50% fruit loss was calculated from firmness values that were related to published data on firmness decreases during storage (see the electronic supplementary material, S3 for calculations) [15]. (b) Red colour intensity. (c) Sugar–acid–ratios. Red lines for the main effect are dashed when pollination treatments did not differ, indicating stronger variety effects than pollination treatments (see table 2 for AICc and likelihood values). Further details and abbreviations are explained in the caption of figure 1.

Figure 3.

Bee pollination had higher pollination success, calculated as the number of fertilized achenes per fruit (see table 2 for AICc and likelihood values). Further details and abbreviations are explained in the caption of figure 1.