How they navigate late summer time meals shortage

Late summer time in Lower Franconia: There are hardly any flowering crops left, and meals for honey bees is changing into scarce. Researchers on the Biocenter have investigated how bees deal with this example.

Plants produce giant portions of nutrient-rich pollen of their flowers—an actual powerhouse for a lot of bugs, together with honey bees: They combine pollen that’s wealthy in protein and fats into the meals they use to nourish their larvae. Younger bees additionally eat the pollen themselves to construct up their energy.

These plant-based vitality sources are extraordinarily vital for honey bees. A scarcity of pollen can delay their improvement, make them extra susceptible to pathogens and extra delicate to pesticides. Scientific research additionally present {that a} extra numerous pollen combine improves the well being and winter survival of bee colonies.

Possible double burden: Food scarcity and pesticides

Late summer time ought to subsequently be a very tough time for honey bees. At this time of the 12 months, few crops are in bloom and the meals provide is dwindling. In addition, the pollen that’s nonetheless out there could comprise residues of pesticides utilized in agriculture.

This double burden may very well be notably onerous on the bees, notably throughout a season that’s already important for them: In late summer time, the long-lived winter bees develop within the hives. Their vitality determines whether or not the colony will survive the chilly season unscathed.

Beehives positioned in decrease Franconia

So what’s the dietary scenario of honey bees in late summer time—notably in agricultural areas? Researchers from the Chairs of “Animal Ecology and Tropical Biology” and “Behavioral Physiology and Sociobiology” on the University of Würzburg’s Biocenter investigated this query. They positioned 36 honey bee colonies at 9 totally different places in Lower Franconia. The proportion of annual cropland assorted considerably round every beehive, starting from 43 to 97% inside a radius of two kilometers.

From the start of July to mid-August, the researchers took samples from the pollen traps in entrance of the beehives each third day. They analyzed which plant species had been visited by the bees and studied pollen variety and pesticide residues. The results have been printed in Agriculture, Ecosystems and Environment.

Same pollen variety and low pesticide ranges

The outcomes shocked the crew led by Professors Ingolf Steffan-Dewenter and Ricarda Scheiner: The variety of the pollen collected was all the time related, no matter whether or not there was a big or small quantity of annual cropland surrounding the beehives. Equally surprising: The pollen contained solely small quantities of pesticides.

So may honey bees additionally thrive in intensively farmed agricultural landscapes in late summer time?

Doctoral pupil Sarah Manzer, the lead creator of the publication, presents a caveat: “Our results should not be overgeneralized. In our study, landscapes with a high proportion of annual cropland still contained many different fields. These can provide flowering resources along field edges as well as a range of pollen-producing weeds within the various crops.” In different international locations with considerably bigger areas of arable land, such because the U.S., the panorama could provide considerably much less meals.

Furthermore, totally different international locations have totally different laws on pesticide use, which may result in various ranges of pesticide contamination. In order to acquire a complete image of the influence of agricultural land on honey bees, additional research in different areas and at different occasions of the 12 months are essential, particularly in spring, when extra pesticides are used.

Clover on the prime of the pollen suppliers

“DNA metabarcoding revealed 140 different pollen species in our 540 pollen samples,” says doctoral pupil Manzer. The bees most continuously collected pollen from clover species, adopted by cornflower pollen and sunflower pollen.

On common, bees carried pollen from 10 totally different crops into the hive over a interval of three days. This is neither a big nor a small quantity. Similar values have been reported in different research. The bees could compensate for the shortage of flowers in late summer time by flying higher distances seeking meals.

Around 60% of samples pesticide-free

The researchers discovered pesticide residues in 39% of the pollen samples. Among the 16 pesticides detected, fungicides (brokers used to fight fungi that harm crops), had been the commonest.

“In terms of concentration, the pesticide doses found are moderate to low; direct lethal effects on honey bees are not to be expected,” says Manzer, based mostly on the outcomes of varied scientific research. However, “we cannot rule out the possibility of gradual damage to bees through negative long-term effects. Furthermore, there is limited knowledge about potential interactions with other pesticides. We also do not know the impact on significantly smaller wild bees, for example.” Further research are wanted to shed extra mild on this subject.