SLU news

Decreasing biodiversity threatens clover seed production

Published: 04 June 2013

The red clover seed yields are decreasing every year since long time. Altered balance between pollinators and pests and changes in the distribution of bumblebee species are contributing factors. This is shown by Ola Lundin in a doctoral thesis from SLU.

Biodiversity in agricultural landscapes is declining, and this also affects various ecosystem services such as crop pollination and pest control and may result in reduced harvests. Ola Lundin from SLU shows in his thesis work that this trend can be seen in the cultivation of red clover seeds.

Red clover is completely dependent on pollination from bees and bumblebees to give a seed yield and the most serious pests are small beetles, clover weevils, which in turn are attacked by parasitic wasps.

Changes in the insect fauna
When Ola Lundin and his colleagues re-inventoried sites with red clover seed cultivation also investigated during the 1930s– 1960s, they found that insect life had changed. The proportion long-tongued bumblebees, which are better at pollinating the clover, had decreased, while the proportion short-tongued species had increased. One explanation for the long-tongued species decline may be that their nectar- and pollen plants have become more rare in the landscape.

Pest management
Ola Lundin has also worked with plant protection issues, and has among other things developed a control threshold, setting the infestation level where it is economically viable to fight clover weevils. The surveys also show that one can reduce the risk of major attacks by avoiding growing seeds close to each other for several years in the crop rotation. This can partly be used as an alternative to chemical control in organic and integrated farming, but Ola Lundin emphasizes the need for more research on environmentally friendly pest management methods.

In terms of chemical pesticides the researchers are of the opinion that one should practice an integrated pest management, and only fight at economically significant attacks that cannot be avoided by other means. Additionally, they recommend farmers to take account of beneficial insects by not spraying the flowering crop.

Overall, the results indicate that pollination and pest control can be compromised when cultivation takes place in large-scale and intensively farmed plains and that this may reduce crop yields. A holistic approach with promotion of beneficial organisms that support agricultural production and crop protection against pests with environmentally friendly practices, can contribute to more sustainable production in agriculture.