Between 2022 and 2023, researchers collected 35 field populations of B. tabaci from 18 major agricultural regions spanning the country, from the tropical vegetable fields of Sanya on Hainan Island to the northern plains of Inner Mongolia. The sampling covered crops as varied as eggplant, tomato, cucumber, chili pepper, sweet potato, and winter melon. Each population was subjected to laboratory bioassays against nine widely used insecticides representing six chemical classes: the biological pesticide abamectin, the neonicotinoids thiamethoxam and imidacloprid, the chloronicotinyl compound thiacloprid, the pyrethroids bifenthrin and deltamethrin, the ketoenol spirotetramat, the diamide cyantraniliprole, and the insect growth regulator pyriproxyfen. Crucially, the team tested adults, eggs, and nymphs separately, recognizing that susceptibility can differ dramatically across the whitefly’s life stages.

The methodology was rigorous and standardized. For adult bioassays, treated cotton leaf discs were placed on agar in small tubes, each receiving 40 to 50 field-collected adults, with mortality scored after 48 hours. Egg assays involved dipping leaves bearing freshly laid eggs into serial insecticide dilutions and counting unhatched embryos seven days later, while nymph assays used root-dipped cotton seedlings infested with synchronized second-instar nymphs, evaluated after two weeks. All results were compared against a laboratory-susceptible reference strain, originally collected in 2008 and never exposed to pesticides, allowing the calculation of resistance factors, the ratio of the field population’s lethal concentration to that of the susceptible baseline. Resistance was classified on a five-tier scale ranging from susceptible to very high, with resistance factors above 100 marking the most alarming category.

The good news first: abamectin remains a rare bright spot. Across 27 tested populations, adults were either fully susceptible or showed only low resistance, and several regions, including Sanya, Jinan, Hangzhou, Beijing, and Yuncheng, actually became more sensitive to the compound in 2023 than in 2022. This suggests that, when used appropriately, abamectin continues to deliver effective field control in China, a finding consistent with earlier nationwide monitoring from 2015 to 2021. In an era when many once-reliable insecticides are failing, the durability of this biological pesticide stands out.

The neonicotinoids tell a very different story. Resistance to imidacloprid ranged from a modest 1.79-fold to a staggering 255-fold in a Sanya population, with very high resistance also recorded in Yuncheng. Thiamethoxam resistance reached high levels in three populations, peaking at 71-fold, and thiacloprid resistance climbed to 140-fold in Sanya. Year-over-year comparisons revealed troubling upward trends in several regions, particularly in central and southern China, where median resistance factors for neonicotinoids exceeded 50. The authors attribute this escalation to prolonged and intensive use of these compounds, and note that cross-resistance mediated by metabolic detoxification enzymes, particularly cytochrome P450s and esterases, likely accelerates the problem. Continued reliance on neonicotinoids, they warn, risks eroding their long-term efficacy entirely.

Pyrethroid resistance presented a more mixed picture. Bifenthrin resistance remained low to moderate nationwide, peaking at around 16-fold, but deltamethrin resistance spanned an extraordinary range, from 2-fold to nearly 105-fold, with the highest value recorded in Yunnan’s Yuanmou region. Southwest China emerged as a pyrethroid hotspot, with median resistance factors exceeding 40. The researchers also compared molecular genotyping data with the bioassay phenotypes and found a crucial nuance: resistance-associated mutations alone do not fully determine phenotypic resistance. Some mutations appeared even in susceptible reference insects, indicating that genetic background, mutation frequency, and metabolic mechanisms all interact to shape real-world resistance. Molecular diagnostics, the authors conclude, must always be interpreted alongside bioassay data.

The newer chemistries, often promoted as solutions to resistance problems, showed their own warning signs. Egg-stage bioassays revealed consistently high resistance to spirotetramat, with resistance factors exceeding 300 in multiple populations and peaking at 357-fold in Suzhou, Anhui. Cyantraniliprole resistance was generally moderate, but a few populations displayed extreme values, with Hangzhou eggs showing a resistance factor above 4,000, and Tianjin above 2,000. Among nymphs, spirotetramat resistance reached 204-fold in Yueyang, while cyantraniliprole resistance peaked at 721-fold in Beijing in 2022, though it declined sharply the following year. Pyriproxyfen, an insect growth regulator used against whitefly nymphs since 1989, showed consistently high resistance across most monitored regions, with values up to 195-fold. The authors suggest that in some areas pyriproxyfen may no longer be suitable for whitefly control at all, a striking verdict for a compound with decades of market history.

Beneath the chemical story lies an evolutionary one. Genotyping of the ace1 acetylcholinesterase gene and the voltage-gated sodium channel gene revealed that resistance-associated alleles are already widespread. At the F331W locus, 15 of 18 populations were homozygous resistant, a legacy of more than 60 years of organophosphate exposure. The pyrethroid-linked mutations L925I and T929V were also common, often appearing as heterozygotes or mixed genotypes that signal ongoing selection and gene flow among populations. Equally significant was the species composition: of the 35 populations sampled, 31 were exclusively the Mediterranean (MED) cryptic species, with only four mixed MEAM1-MED populations, all from Sanya. MED, known for its superior insecticide tolerance and more efficient virus transmission, has essentially completed its displacement of MEAM1 across China, likely because it survives better under intensive neonicotinoid and pyriproxyfen spraying.

The virus dimension amplifies the concern. TYLCV, transmitted exclusively by B. tabaci, was detected in 10 of 11 tomato-derived populations, with infection rates exceeding 95 percent in nearly all of them. The virus also appeared in chili, cucumber, watermelon, and hami melon samples, though at more variable rates. Previous research has shown that TYLCV infection actually enhances MED survival and reproduction while shortening development time, creating a feedback loop in which the most insecticide-resistant vector is also the most efficient virus spreader. This dual threat, resistant insects and rampant virus, is precisely the scenario that integrated pest management programs are designed to prevent, and the study’s authors argue it demands coordinated action.

The path forward, the researchers emphasize, is resistance-informed and region-specific management. Because resistance profiles differ sharply across China’s cropping systems and climates, a one-size-fits-all spraying schedule is doomed to fail. Instead, they recommend rotating insecticides with distinct modes of action, selecting compounds according to the susceptibility of specific life stages, using molecular monitoring as an early-warning system for emerging resistance alleles, and pairing chemical control with virus suppression tactics such as removing infected plants, managing weed hosts, and reducing vector populations early in the crop cycle. Although the survey focused on China, the patterns it documents, rapid susceptibility shifts, strong regional selection pressures, immature-stage resistance, MED dominance, and widespread virus transmission, mirror challenges reported from Spain and Israel to Australia and Pakistan. Continuous surveillance, cross-regional data sharing, and adaptive management, the authors conclude, will be essential to curb further resistance escalation and protect agricultural productivity far beyond China’s borders.

Subject of Research: Nationwide monitoring of insecticide resistance, cryptic species composition, and TYLCV prevalence in Bemisia tabaci across China

Article Title: Nationwide spatiotemporal monitoring of insecticide resistance in Bemisia tabaci in China (2022–2023)

Article References: Yang, J., Li, Q., Zhang, Y., Ji, Y., Du, H., Guo, Z., Xie, W., Wang, S., Wu, Q., Zhang, Y., & Yang, X. (2026). Nationwide spatiotemporal monitoring of insecticide resistance in Bemisia tabaci in China (2022–2023). Journal of Agriculture and Food Research, 31, Article 103339. https://doi.org/10.1016/j.jafr.2026.103339

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103339

Keywords: Bemisia tabaci, insecticide resistance, whitefly, neonicotinoids, TYLCV, MED cryptic species, pyriproxyfen, spirotetramat, cyantraniliprole, resistance monitoring, integrated pest management, China