Pymetrozine Explained

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.[1] [2]

Mechanism of action

Pymetrozine is a neuroactive insecticide that selectively affects chordotonal mechanoreceptors present in the legs of sap-feeding insects.[3] It targetes specific ion channels in the nervous system of insects, particularly the transient receptor potential vanilloid (TRPV) channels.[4] 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).[5] 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. [6]

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.[7] 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.[8] Exposure to 3-PCA has been reported to cause developmental toxicity in zebrafish.[9]

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).[10]

Notes and References

  1. Li . Cun . Yang . Ting . Huangfu . Weiguo . Wu . Yinliang . 2011-02-01 . Residues and dynamics of pymetrozine in rice field ecosystem . Chemosphere . 82 . 6 . 901–904 . 10.1016/j.chemosphere.2010.10.053 . 21074245 . 2011Chmsp..82..901L . 0045-6535.
  2. Ausborn . Jessica . Wolf . Harald . Mader . Wolfgang . Kayser . Hartmut . 2005-12-01 . The insecticide pymetrozine selectively affects chordotonal mechanoreceptors . Journal of Experimental Biology . en . 208 . 23 . 4451–4466 . 10.1242/jeb.01917 . 16339866 . 1477-9145.
  3. Web site: T3DB: Pymetrozine . 2024-10-29 . www.t3db.ca.
  4. Wang . Li-Xiang . Niu . Chun-Dong . Salgado . Vincent L. . Lelito . Katherine . Stam . Lynn . Jia . Ya-Long . Zhang . Yan . Gao . Cong-Fen . Wu . Shun-Fan . 2019-01-01 . Pymetrozine activates TRPV channels of brown planthopper Nilaparvata lugens . Pesticide Biochemistry and Physiology . 153 . 77–86 . 10.1016/j.pestbp.2018.11.005 . 30744899 . 2019PBioP.153...77W . 0048-3575.
  5. Web site: California Office of Environmental Health Hazard Assessment (OEHHA). 2024-10-29 . oehha.ca.gov.
  6. Web site: Hertfordshire . University of . Pymetrozine (Ref: CGA 215944) . 2024-11-07 . sitem.herts.ac.uk.
  7. Wei . Haifeng . Chen . Guiquan . Yang . Xiaoyun . 2022-05-04 . Residues and degradation dynamics of pymetrozine and chlorpyrifos in rice field ecosystem . Journal of Environmental Science and Health, Part B . en . 57 . 5 . 339–349 . 10.1080/03601234.2022.2056393 . 35362360 . 0360-1234.
  8. Liang . Ximei . Guan . Fangling . Ling . Zhiyou . Wang . Honghong . Tao . Yunwen . Kraka . Elfi . Huang . Huajun . Yu . Chenglong . Li . Danping . He . Jinbao . Fang . Hansun . 2022-02-05 . Pivotal role of water molecules in the photodegradation of pymetrozine: New insights for developing green pesticides . Journal of Hazardous Materials . 423 . 127197 . 10.1016/j.jhazmat.2021.127197 . 0304-3894.
  9. Cho . Yerin . Jeon . Hwang-Ju . Kim . Kyeongnam . Kim . Chaeeun . Lee . Sung-Eun . 2023-03-15 . Developmental toxicity of a pymetrozine photo-metabolite, 3-pyridinecarboxaldehyde, in zebrafish (Danio rerio) embryos: Abnormal cardiac development and occurrence of heart dysfunction via differential expression of heart formation-related genes . Ecotoxicology and Environmental Safety . 253 . 114654 . 10.1016/j.ecoenv.2023.114654 . 0147-6513. free . 36801540 .
  10. (National Bureau of Statistics of China, 2020, Preetha et al., 2010)

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