The western honey bee is one of more than
300 bee pollinator species occurring in Florida
that play a role in the pollination of agricultural
crops and natural and managed landscapes.
The western honey bee is conceivably the most
important pollinator in Florida and American
agricultural landscapes. The honey bee is
credited with approximately 85% of the pollinating
activity necessary to supply one-quarter to
one-third of the nation’s food supply. There
are also over 3,000 registered beekeepers
in Florida, managing a total of more than
400,000 honey bee colonies and producing between
10 - 20 million pounds of honey annually.
Urban landscape ecosystems are a complex and
diverse interaction between people, plants,
insects, and the environment. Over 90% of
Floridians live among urban landscapes, often
in close proximity to commercially managed
bee hives, although the hives may be kept
outside of city limits. How­ever, a growing
number of small-scale beekeepers and hobbyists
maintain colonies in urban landscapes. Bees
can fly 2 to 5 miles in any direction to search
for pollen and nectar, so colonies located
in proximity of managed landscapes can be
affected by the pesticides used.
Protecting honey bees and other pollinators
from pesticide impacts is important to the
sustainability of agriculture and urban landscapes,
but can be challenging. A primary challenge
is the fact that urban landscapes can be highly
disturbed harsh environments with frequent
pest outbreaks. Consequently pesticide applicators
must determine if there is a clear hazard
to managed or wild populations of bees, and
other pollinators in these environments when
managing pests. Potential exposure of bees
to pesticides can vary greatly depending on
the type of pesticide, formulation, application
method, label restrictions, and other factors.
The goal in using a pesticide is to achieve
maximum success with minimum negative impact,
and these factors should always be considered
in pesticide selection. I’m Dr. DeBusk and
this video will discuss pollinators and how
to protect them from pesticide exposure.
Native bees, butterflies and other pollinators
are wildlife, deserving of protection in the
same way birds such as raptors and songbirds
are protected. Unfortunately, honey bee health
is in decline, and some native bees and butterflies
are threatened. Honey bees are well studied
because of their eco­nomic importance. From
April 1, 2014 to April 1, 2015, the U.S. lost
42 percent of its honey bee colonies, and
winter losses since 2006 are generally around
30 per­cent every year. Beekeepers consider
annual losses of 15% to be acceptable, and
losses greater than this make it difficult
or impossible to remain profitable.
Most researchers agree that a combination
of factors is causing declines in bee and
pollinator populations, including parasites,
pathogens, loss of habitat or flowers that
provide pollen and nectar, and pesticide exposure.
Each of these has been found to negatively
affect bees, but there is also evidence the
combi­nation of stresses is especially harmful.
Bees and other pollinators depend on flowers
for food - nectar provides carbohydrates,
while pollen is their source of protein. Flowerless
landscapes like mowed lawns with strict weed
control, heavily paved areas of cities and
fields with no plant diversity contain little
food for bees which leads to poor nutrition
and compromised immune systems. Nutritionally
weakened bees are more susceptible to disease
and pesticides.
Many pests and pathogens also affect bees.
The Varroa mite, a parasite of honey bees,
is one of the most destructive factors causing
honey bee decline. It attaches to the body
of the adult bee or larvae and weakens the
bee by sucking fat bodies, as well as vectoring
viruses. Other parasites and pathogens may
become a more serious problem in hives weakened
by Varroa mite.
In some cases, the flowers that bees forage
on have pesticide residue on the petals or
in the nectar and pollen. These chemicals
can kill bees directly or cause a variety
of sublethal effects such as impairing their
ability to find their hive or provide food
for their larvae. The toxicity of pesticides
for bees ranges from highly toxic to relatively
safe, depending on the specific chemical and
the exposure, although long-term exposure
to low doses has not been investigated for
many types of pesticides. In some cases the
impacts are worse when pollinators are exposed
to combi­nations of pesticides. Since bees
forage through a wide range of landscapes,
they may be exposed to a complex mixture of
many different chemicals.
One group of insecticides, the neonicotinoids
(neonics), has recently been studied intensively
by scientists to determine their impact on
bees, primarily because of their widespread
agricultural use on field crops. However,
neonics are also used by professionals and
homeown­ers in landscapes and gardens. Neonics
are a class of insecticide that acts on the
insect’s nervous sys­tem. They are more
selective, having greater toxicity to insects
than mammals, and safer for humans to use
than most old classes of insecticides. They
are toxic when ingested or through direct
contact. The most widely used neonics -- imidacloprid,
thiamethoxam, clothianidin and dinotefuran
-- are all highly toxic to bees. Products
containing these active ingredients have bee-warning
boxes on the label with important instructions
for limiting bee exposure that must be followed.
Neonics move upwards in xylem sap internally
within plants when applied to the plant, where
they can later reach nectar and pollen. Pesticides
remain primarily in leaf tissue following
a foliar spray.
Neonics, like most insecticides, will cause
sig­nificant harm if pollinators come directly
into contact with them. This exposure generally
occurs when a neonic is misused and sprayed
on a blooming plant or one that will bloom
soon. This does not imply that neonics are
the only insecticide class toxic to bees and
other pollinators. There are others; check
the Environmental Hazards section of product
labels for this information. That section
will contain statements regarding precautionary
measures for minimizing exposure of bees and
pollinators.
Bees and other pollinators can also collect
contam­inated pollen or nectar from the treated
plants and bring it back to their colony,
creating high risk of harm to the colony.
Research studies have demonstrat­ed native
bees and honey bees can be harmed by small
amounts of pesticides in nectar and pollen.
When a neonic is applied as a soil drench,
it may persist for a year or more, especially
in woody plants, and can also move into weeds
or flowers growing over the drenched soil.
If some of the insecticide moves into pollen
or nectar it may not kill bees directly, but
it can act as a stressor to affect larval
growth, susceptibility to diseases, navigation
or winter survival. How we manage pests in
ornamental landscapes has an impact on pollinators.
The following section will explain the best
ways to minimize pollinator exposure to pesticides.
Beyond complying with the label, applicators
are urged to consider and use the following
additional approaches to reduce the duration
and risk of pesticide impacts to honey bees
and other pollinators. The following practices
can aid in the protection of managed and non-managed
pollinators and should be taken into consideration
even if the landscape is not actively hosting
honey bee colonies or other managed bees.
Pest management approaches by professionals
vary, so each recommendation may not be applicable
to every situation. For the first recommendation,
this tool can be found at the web address
shown here and will allow you to become aware
of the locations of commercially managed bee
hives. Select “Information for Growers.”
On the Information for Growers page, click
“Online Map.”
Pesticides should never be applied unless
they are necessary to maintain plant health.
Using preventive blanket sprays, where pesticides
are sprayed several times a year on a calendar
basis, has been shown to create more pest
problems than it solves. Not only do cover
sprays create potential for pesticide runoff
and increased human and pet exposure, they
actually­ create pest problems by suppressing
predators, parasitoids and diseases that keep
plant pests under control. It is not unusual
to observe outbreaks of spi­der mites, aphids
and scale insects where pesticides are used.
Only spray plants and portions of the landscape
infested with pests, and only if it is necessary.
First, most bees and other pollinators forage
during the day from 8 am to 5 pm, so if you
can spray at night or in the early morning,
if feasible, you can reduce the risk of accidentally
spraying them. Be conscious of early days
and longer hours in the peak of the summer,
when bees will typically forage earlier and
longer. Second, pollinators are attracted
to flowers. Anything that has flowers or is
about to flower is a higher risk than a plant
that is past bloom. If you can remove the
flowers by mowing or pruning from around the
treated plant, and anywhere your applica­tion
may drift, you can significantly reduce risk
to bees and other pollinators. Third, honey
bees fly when the air temperature is above
55°F - 60°F. Finally, always check the landscape
for bee activity immediately before an application,
when the pesticide label bee protection statements
apply.
Bees require water to cool the hive and feed
the brood. Avoid contaminating standing water
with pesticides or draining spray tank contents
onto the ground, creating puddles to which
bees may be attracted. Be mindful that contaminated
water can also come from runoff, improper
storage, or spills.
It is clear to most people that insecticides
sprayed onto open flowers can be highly toxic
to bees, even if they are sprayed early in
the morning or at night when bees are not
present. However, some may not realize insecticides
sprayed in the two-week peri­od before a
tree flowers can also be toxic to bees. Insecticides
that tend to volatilize, especially those
formulated as emulsifiable concentrates, can
vaporize off the leaf surface and contaminate
flowers after they open. Although this level
of contamination is very low, it may still
affect bees because some insecticides, like
the neonics, can affect bees at concentrations
as low as 10 parts per billion.
Some systemic insecticides like most of the
neonics may be partially absorbed by sprayed
leaves and move systemically in the plant.
Only a very small amount of residue is absorbed
into leaf tissue, not enough to provide control
of insect pests, but it may be enough to cause
sublethal effects to bees if it moves into
the pollen or nectar. Recent studies on cherry
trees indicate if they are sprayed with imidacloprid
after the flowering period is over, the amount
of imidacloprid found in nectar the following
year is not a serious threat to pollinators.
Recent research indicates fungicide brought
back to the hive on contaminated pollen or
on work­ers’ bodies interferes with the
function of beneficial fungi in the hive.
Several types of fungi grow in hives and the
chemicals they secrete pro­vide a natural
defense against bee diseases. They also play
an important role in producing bee bread,
a fermentation product of pollen which requires
fungi. Bee bread is a critical protein source
for bee lar­vae and adults. Recent studies
have shown bees exposed to fungicides do not
produce as much bee bread in their hives.
Furthermore, certain fungicides can disable
the detoxification enzymes of insects, which
can greatly increase the tox­icity of certain
insecticides to bees. Several studies have
reported pollen contaminated with captan,
ziram, iprodione, chlorothalonil and man­cozeb
may be harmful to bee larvae when they eat
it.
Some mixtures of fungicides with insecticides
may be more toxic to bees than the insecticide
alone. When propiconazole is mixed with pyrethroid
insecticides, it may increase the toxicity
of the insecticide to bees. Also when propaconizole
and other fungicides in that class, such as
tebuconazole, myclobutanil and triflumizole,
are mixed with acetamaprid, the solution becomes
fivefold or more toxic to bees than acetamaprid
by itself.
Choose insecticides that are highly selective
to a spe­cific type of insect and so have
low toxicity for others. An EPA Reduced Risk
product is a conventional pesticide that poses
less risk to human health and the environment
than existing conventional alternatives. Other
characteristics of low impact pesticides are
those that break down rapidly after applica­tion
and therefore have minimal impact on pollinators
and natural enemies. However, using these
products requires some knowledge about their
relative toxicity to beneficial insects and
their potential to cause phytotoxicity. I
hope you learned more about the factors that
affect pollinator health and the risk-reduction
approaches that applicators can use. The next
video will be on low risk pesticides that
can be safely used to manage ornamental pests.
