Missing bees make fruit unhealthier

Exposure to insects also affects the nutrient composition of fruits

Wild bee on an almond blossom © Alexandra-Maria Klein
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Bees and other pollinator insects are even more important than they thought: if they are absent, not only will the yield of some fruits decrease, but their nutritional composition will also change. For example, almonds contain less healthy fatty acids and less vitamin E if the pollinators fail. This is proven by the experiment of a team of German and US researchers.

Honeybees, but also wild and other insects are extremely important for the pollination of most crops, they lack apple tree, strawberry, tomato, coffee tree and others bear no fruit. But it is precisely these insects are rapidly falling worldwide, because pesticides and monocultures destroy their livelihoods. Just last year, a study showed that wild pollinators in many places are crucial for crop yields.

Nets against bee pollinators

So far, the question has been open as to whether possibly other pollination methods, for example by hand or with machines, can replace the role of insects. It was also unclear whether a missing bee pollination changed the composition of the fruits. Alexandra-Maria Klein from the University of Freiburg and her colleagues have now investigated this on California almond trees.

For their study, the researchers encased a portion of the almond trees on a plantation in cages that kept away bees and other pollinator insects. Part of the trees wrapped in this way was pollinated by hand, another part remained untouched. In addition, part of the almond trees had their fertilizer omitted, others less watered. This should show to what extent these treatments together and separately influence almond yield and nutrient composition.

"Almonds with a high content of oleic acid as opposed to linoleic acid are the most healthy for consumers, " Klein and her colleagues explain. Because oleic acid is considered the component of the tonsils, which explains its positive effect on the cardiovascular system. Linoleic acid, on the other hand, is an omega-6 fatty acid that is more likely to have negative health effects. display

Less yield and less healthy ingredients

The evaluation of the experiments showed two things: First, even a hand pollination can not replace the missing bees. Almond trees dusted by hand produce only very small almonds. Bees pollinated trees yielded 200 percent more yield, the researchers report. Fertilization and irrigation alone had hardly any influence on the yield. Obviously the tree can not compensate for deficiencies in pollination, but lack of water or nutrients is, to some extent, already.

On the other hand, the lack of pollination also markedly changed the nutritive composition of the almonds: the almonds that bees bred contained more of healthy oleic acid and less linoleic acid. Also, the content of vitamin E was higher, as the researchers report. However, the almonds they bred got worse on both counts. In addition, they lacked water and fertilizer, and the vitamin E content dropped even more.

"These results show that pollination alters the value and quality of almonds, " Klein and her colleagues note. This underscores the great importance of bees and other insects as bestuniversals also for our own health. (PLoS ONE, 2014; doi: 10.1371 / journal.pone.0090082)

(University of Freiburg im Breisgau / PLOS ONE, 10.06.2014 - NPO)