commonly used for crop protection, with global market revenues projected to be
over US$50 billion in 2019 [51].
Other traditional pests and diseases such as foulbrood, chalkbrood, and Nosema
fungal infection are not believed to be directly responsible for causing CCD, because
they did not have a history of inducing CCD-like symptoms. However, the complexity of CCD due to a combination of stressors does not rule out the possibility that
any previously singular malady exacerbates a hive situation that can lead to
CCD [52].
A preliminary 2014–2015 honey bee loss report provided in collaboration
between the USDA and Apiary Inspectors of America indicates that CCD has not
been reported as the most troubling mortality cause to Western commercial honey
bees in recent years, but its individual components may still be significant issues
leading to current annual mortality rates that are still higher than acceptable levels
[47]. This annual report relies on self-reported beekeeper survey data (Table 1.3;
Fig. 1.3).
4.2.2 Insecticides
Neonicotinoid insecticides are effective insecticides chemically similar to nicotine
and operate as selective agonists of nicotinic acetylcholine receptors, which are
excitatory neurotransmitter receptors in insects. It is an extremely common class of
pesticide used on 95% of United States corn and canola crops and the majority of
numerous other crops such as cotton and a wide variety of popular fruits and
vegetables. Besides direct crop application, it is applied to seeds for planting
seasons. Neonicotinoids represent one-quarter to one-third of the global insecticide
market and is thus a highly profitable product [54, 55].
Assertions of neonicotinoid pesticides’ negative effects upon bees have been a
source of contention since CCD came to light, with studies pointing to insecticide
correlations.
There is evidence that sublethal doses of neonicotinoid pesticide—doses that do
not cause direct mortality—have the potential to cause a variety of problems in
foraging honey bees, including memory and learning dysfunction and interference
with navigation. Because honey bees are social creatures that communicate direction
and distance to food sources by way of the spatial waggle dance, these sublethal
effects can prevent foragers from finding food sources or returning to their hives.
Either risk is highly threatening to colony health, as the ongoing loss of adult bees
stresses the entire social structure and leads to colony collapse.
A study published in 2012 described an experiment with pesticide-exposed
foraging honey bee populations, using thiamethoxam at commonly encountered
yet nonlethal doses. Scientists found substantial mortality due to homing failure,
where exposed foragers were far less likely to return to the colony than control bees:
about 10% to over 30% of exposed honey bees would fail to return when foraging on
pesticide-treated crops. The probability that a bee forager would die due to homing
20
C. Li
over US$50 billion in 2019 [51].
Other traditional pests and diseases such as foulbrood, chalkbrood, and Nosema
fungal infection are not believed to be directly responsible for causing CCD, because
they did not have a history of inducing CCD-like symptoms. However, the complexity of CCD due to a combination of stressors does not rule out the possibility that
any previously singular malady exacerbates a hive situation that can lead to
CCD [52].
A preliminary 2014–2015 honey bee loss report provided in collaboration
between the USDA and Apiary Inspectors of America indicates that CCD has not
been reported as the most troubling mortality cause to Western commercial honey
bees in recent years, but its individual components may still be significant issues
leading to current annual mortality rates that are still higher than acceptable levels
[47]. This annual report relies on self-reported beekeeper survey data (Table 1.3;
Fig. 1.3).
4.2.2 Insecticides
Neonicotinoid insecticides are effective insecticides chemically similar to nicotine
and operate as selective agonists of nicotinic acetylcholine receptors, which are
excitatory neurotransmitter receptors in insects. It is an extremely common class of
pesticide used on 95% of United States corn and canola crops and the majority of
numerous other crops such as cotton and a wide variety of popular fruits and
vegetables. Besides direct crop application, it is applied to seeds for planting
seasons. Neonicotinoids represent one-quarter to one-third of the global insecticide
market and is thus a highly profitable product [54, 55].
Assertions of neonicotinoid pesticides’ negative effects upon bees have been a
source of contention since CCD came to light, with studies pointing to insecticide
correlations.
There is evidence that sublethal doses of neonicotinoid pesticide—doses that do
not cause direct mortality—have the potential to cause a variety of problems in
foraging honey bees, including memory and learning dysfunction and interference
with navigation. Because honey bees are social creatures that communicate direction
and distance to food sources by way of the spatial waggle dance, these sublethal
effects can prevent foragers from finding food sources or returning to their hives.
Either risk is highly threatening to colony health, as the ongoing loss of adult bees
stresses the entire social structure and leads to colony collapse.
A study published in 2012 described an experiment with pesticide-exposed
foraging honey bee populations, using thiamethoxam at commonly encountered
yet nonlethal doses. Scientists found substantial mortality due to homing failure,
where exposed foragers were far less likely to return to the colony than control bees:
about 10% to over 30% of exposed honey bees would fail to return when foraging on
pesticide-treated crops. The probability that a bee forager would die due to homing
20
C. Li