Common insecticide is harmful to bees in any amount
For the average bee, every little bit counts

Date:
August 2, 2021
Source:
University of California - Riverside
Summary:
The dangers of neonicotinoid insecticides likely can't be watered
down.

That's the conclusion of a new study showing an insecticide made
for commercial plant nurseries is harmful to a typical bee even
when applied well below the label rate and the plant receives high
levels of irrigation.



FULL STORY ==========================================================================
A new UC Riverside study shows that a type of insecticide made for
commercial plant nurseries is harmful to a typical bee even when applied
well below the label rate.


==========================================================================
The study was published today in the journal Proceedings of the Royal
Society B: Biological Sciences.

Chemically similar to nicotine, neonicotinoids are insecticides that
protect against plant-consuming insects like aphids, but seriously harm beneficial insects, like bees. They are widely used by commercial growers.

Much research has focused on their use in food crops like canola, in
which they are typically applied at low doses. However, this study is
one of the few to examine neonicotinoid application in potted ornamental plants, which can represent more potent, acute sources of exposure to
the toxin for bees.

"Neonicotinoids are often used on food crops as a seed treatment,"
explained UCR entomologist and lead study author Jacob Cecala. "But
they're usually applied in higher amounts to ornamental plants for
aesthetic reasons. The effects are deadly no matter how much the plants
are watered." Cecala said he was surprised by this result, given that neonicotinoids are water soluble. Going into the study, he assumed that
more water would dilute the amount of harm they caused the bees. The researchers were also curious whether increased watering could benefit
bees despite insecticide exposure by increasing the quantity or quality
of nectar offered by the plants.



==========================================================================
To test these assumptions, the researchers raised bees on flowering native plants in pots that either received a lot of watering, or a little. Plants
were selected based on their popularity at nurseries, drought tolerance
to ensure blooming even without much water, and their attractiveness to
bees. In addition, half the plants were treated with the insecticide.

Though increased water decreased the pesticide's potency in the nectar
of the flowers, the negative effects on bees were still observed.

"Unfortunately, we observed a 90% decrease in the bees' reproduction
with both high and low levels of irrigation," Cecala said.

This study is also one of the few to examine neonicotinoid effects via ornamental plants on solitary bees, which make up more than 90% of native
bee species in North America, and an even higher percentage in California.

Solitary bees are not bees who have left the hive and are now alone. This
is a type of bee that lives alone, does not produce honey, and does
not have a queen or live in a hive. Because they do not have a store of
honey to protect, they are also not aggressive.



========================================================================== "Solitary bees are more representative of the ecosystem here, and they
are potentially more vulnerable to pesticides," said UCR entomologist
and study co- author Erin Rankin.

If a worker bee that is social -- like the honeybee -- gets exposed
to insecticide and dies, it won't necessarily affect the longevity of
the hive.

However, if a solitary bee dies, its lineage is cut short.

In this study, the researchers used alfalfa leafcutter bees, which make
their nests in tunnels and lay eggs one at a time. They are very similar
to California's solitary native bees and are part of a genus that can
be found worldwide.

The first time Cecala and Rankin tried this experiment, they used the concentration of insecticide recommended on the product label. All the
bees died in a matter of days.

The next time they ran the experiment, they used a third of the
recommended dose and still found negative effects on reproduction, the
ability of the bees to feed themselves, and overall fitness. "It almost completely wiped them out," Cecala said.

Though this study used a neonicotinoid product formulated for nurseries, formulations of similar products for home gardeners also tend to be
highly concentrated.

Plants in nurseries or residential backyards represent a smaller total
area than food plant fields like corn or soy. However, high-potency neonicotinoid products can have a big effect even in small areas. In
2013, neonicotinoids applied to flowering trees in a retail parking
lot in Oregon caused a massive bumblebee die off, with more than 25,000
found dead.

The researchers recommend that nurseries quantify the amount of pesticides
that are making their way into flowers given their watering and pesticide regimes, and consider alternative management practices that reduce harm
to bees and the ecosystems dependent on them.

"It's not as simple as 'don't use pesticides' -- sometimes they're
necessary," Cecala said. "However, people can look for a different
class of insecticide, try to apply them on plants that aren't
attractive to bees, or find biological methods of pest control." ========================================================================== Story Source: Materials provided by
University_of_California_-_Riverside. Original written by Jules
Bernstein. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jacob M. Cecala, Erin E. Wilson Rankin. Pollinators and plant
nurseries:
how irrigation and pesticide treatment of native ornamental plants
impact solitary bees. Proceedings of the Royal Society B: Biological
Sciences, 2021; 288 (1955): 20211287 DOI: 10.1098/rspb.2021.1287 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210802103056.htm

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