Chemistry Reference
In-Depth Information
role in crop growth, this is a concern for agriculture and it is under inves-
tigation. Although the bee population has been in decline, there is no clear
evidence implicating the neonicotinoids. There are several other possible fac-
tors including a parasitic mite that may be the cause. Nosema bombi is a
parasite commonly found in bees. One study showed that declining bee pop-
ulations are associated with both high Nosema bombi infection levels and
low genetic diversity [38]. Nonetheless, governments have taken steps to pro-
tect bees from possible harm. The European Commission has announced a
two-year ban on clothianidin, imacloprid, and thiamethoxam [39]. The EPA
is requiring manufacturers of imidacloprid, dinotefuran, clothianidin, and thi-
amethoxam to include language prohibiting use when bees are foraging or
when plants are flowering [40].
There are organochlorine insecticides such as DDT, a group 3, sodium
channel modulator. Others such as chlordane, dieldrin, and endosulfan are
members of group 3, GABA-gated chloride channel antagonists. Because of
their persistence in, and detrimental effect on, the environment, especially on
birds, they are no longer widely used in most countries.
Cl
Cl
Cl
Cl
Cl
Cl
H
ClCl
3
Cl
O
O
Cl
Cl
S
O
Cl
Cl
Cl
Cl
O
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
DDT
Chlordane
Dieldrin
Endosulfan
Another class of chemicals in group 3 is the phenylpyrazoles. Fipronil is a
member of this class. Fipronil blocks chloride channels gated by the inhibitory
neurotransmitter gamma-aminobutyric acid (GABA) and also those gated by
glutamate [41]. Fipronil is also widely used as a household and veterinary
insecticide for the control of insects such as termites, cockroaches, and ants.
As with some neonicitinoid pesticides, there is a concern with the effect of
fipronil on honeybees. The European Union has voted in favor of restricting
the use of fipronil on seeds to only seeds sown in greenhouses [42].
O
NC
S
CF
3
N
NH
2
N
Cl
Cl
CF
3
Fipronil
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