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Chemical compound
Pymetrozine is an insecticide in the pyridine-azomethine chemical class, primarily utilized for controlling homopteran pests, such as aphids and whiteflies, in agricultural settings. Its mode of action selectively targets the feeding behavior of sap-feeding insects, causing them to cease feeding soon after ingestion. This unique mechanism limits its impact on non-target organisms, including beneficial insects. Pymetrozine has been extensively used on rice, potatoes, a wide variety of vegetable brassica crops and various other crops as an alternative to organophosphorus pesticides.
Mechanism of action.
Pymetrozine is a neuroactive insecticide that selectively affects chordotonal mechanoreceptors present in the legs of sap-feeding insects. It targetes specific ion channels in the nervous system of insects, particularly the transient receptor potential vanilloid (TRPV) channels. It is in IRAC group 9B. These channels, which consist of two key protein subunits, play a crucial role in sensory signal transduction. When pymetrozine binds to these channels, it alters their activity, leading to increased sensitivity and disruption of normal neuronal signaling. This mechanism results in impaired movement and behavior in target insects. Pymetrozine acts both on the plant's surface and internally, moving through vascular channels in multiple directions. It penetrates leaf tissues and remains effective when applied to either foliage or soil. Its internal movement within the plant does not interfere with growth processes, even after leaf-based applications.
Safety.
Pymetrozine can cause cancer according to The Environmental Protection Agency (EPA).
Pymetrozine is of low acute toxicity to humans, mammals, birds, aquatic organisms, and bees. It is a respiratory tract irritant and ingestion may affect major organs at high doses. It may cause reproductive or developmental defects. 
Ecotoxicity.
Pymetrozine has low off-target effects.
The half-life of pymetrozine in water, soil, and rice plants is 2.81, 6.95, and 3.70 days respectively.
3-pyridinecarboxaldehyde (3-PCA) and 4-amino-6-methyl-2 H-1,2,4-triazine-3-one are the primary degradation products of pymetrozine on photodegradation. Exposure to 3-PCA has been reported to cause developmental toxicity in zebrafish.
Use.
The annual usage of pymetrozine was at least 4.45 × 103 t in China according to its consumption (150 g/ha) and area of rice field (2.97 × 107 ha).
References.
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