Long-term monitoring of insecticide resistance in pink bollworm in Israeli pima cotton fields

Status of insecticide resistance and detoxification enzymes activity in pink bollworm, Pectinophora gossypiella (Saunders) populations from India

Insecticide bioassays conducted across major cotton-growing regions of India revealed a notable increase in LC50 values in field populations compared to the laboratory-susceptible strain, confirming reduced susceptibility and development of resistance.

Early indicators of Bt resistance: Variation in Cry toxin susceptibility in field populations of Helicoverpa armigera (Hübner) from India

Rapid expansion of insecticide resistance in Acyrthosiphon kondoi and opportunities to improve chemical and biological control

The bluegreen aphid (Acyrthosiphon kondoi) is a global pest of pasture and legume crops, damaging plants through feeding and the transmission of plant viruses. Since 2018, Australian growers have reported insecticide control failures involving A. kondoi, with subsequent bioassays confirming the first cases of insecticide resistance in this species worldwide. To better inform management strategies, we conducted a surveillance programme of 36 field populations across southern Australia, testing for resistance to organophosphates, carbamates, and synthetic pyrethroids. Resistance was detected in 19 populations, most commonly within alfalfa (Medicago sativa) seed production regions. We then generated baseline sensitivity data for two insecticides, sulfoxaflor and flonicamid, recently introduced for A. kondoi control in Australia, and found that both provide promising new options for resistance management. In parallel, we assessed biological control potential by surveying parasitoid wasps attacking A. kondoi. Aphidius ervi was the only species detected parasitising A. kondoi across southern Australia. Follow-up laboratory assays demonstrated high parasitism and successful emergence of A. ervi from A. kondoi and more variable performance across co-occurring aphid pests, highlighting its broader biocontrol potential in pasture and legume systems. Together, these findings demonstrate the rapidly expanding distribution of insecticide resistance in A. kondoi, confirm the value of newly available insecticides, and identify a key parasitoid for integration into management strategies. These findings provide a foundation for integrated management approaches to slow resistance evolution in A. kondoi in Australia and elsewhere.

Susceptibility of Culex quinquefasciatus to insecticides in the industrial areas of Koumassi, Vridi, and Yopougon in Abidjan, Ivory Coast, during the rainy season

Insecticide resistance in Culex quinquefasciatus is an important concern for urban vector control because it can reduce the effectiveness of chemical interventions and undermine public acceptance of insecticide-based mosquito control. This study assessed the susceptibility of C. quinquefasciatus populations collected during the 2025 rainy season from the industrial zones of Koumassi, Vridi (Port-Bouët), and Yopougon in Abidjan, Côte d’Ivoire. Larvae were collected from residential, non-chemical industry, chemical industry, and chemical and other materials industry sites, reared to adulthood, and 3–5-day-old females were tested using WHO susceptibility assays. Diagnostic, 5×, and 10× concentrations of pyrethroids were evaluated alongside 5% malathion, 0.1% bendiocarb, and 4% DDT, while 4% piperonyl butoxide (PBO) assays were used to investigate metabolic resistance. At diagnostic concentrations, resistance or suspected resistance was observed across the three industrial zones, whereas malathion produced 98–100% mortality at the Vridi residential site and the INC and ICAM sites in Yopougon. Mortality at 10× pyrethroid concentrations remained below 98% across the sites evaluated, indicating high resistance intensity. Malathion produced the shortest Kdt50/Kdt95 values, reaching 36.34/64.24 min in Yopougon. PBO did not consistently restore susceptibility, indicating that monooxygenases were not the sole resistance mechanism. These findings demonstrate substantial insecticide resistance and support continued susceptibility monitoring to guide effective vector-control strategies in Abidjan’s industrial areas.

Efficacy of Plinazolin and Selected Conventional Insecticides for Control of Pepper Weevil ( Anthonomus eugenii ) Adults: A Laboratory Bioassay

Pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae), is one of the most economically troublesome pests of pepper production in the southern and south eastern USA. Management of this pest is challenging due to the internal larvae feeding habitat and development, limiting exposure to synthetic insecticides and reducing control efficacy. The effectiveness of available insecticides is further constrained by their non-target effects and the potential for resistance development. Here, we investigated the efficacy of the novel insecticide plinazolin (ISM-555) and selected conventional insecticides against adult pepper weevil under laboratory conditions. Adult mortality and incapacitation were assessed following insecticide exposure. Plinazolin and oxamyl (Vydate® C-LV) caused the highest adult mortality, while thiamethoxam (Actara®) also exhibited significant mortality compared with the untreated control. The results demonstrate the potential of plinazolin as an effective tool for pepper weevil management and provide baseline susceptibility data to facilitate monitoring of pepper weevil populations. Incorporating insecticides with different modes of action into rotation programs may improve control efficacy, and reduce the risk of resistance via integrated pest management (IPM) strategies for pepper weevil. © The Authors 2026

Pyrethroid resistance intensity and mechanisms in Anopheles gambiae sensu lato (Diptera: Culicidae) from Oyo State, Nigeria.

BACKGROUND Pyrethroid resistance in Anopheles gambiae sensu lato (s.l.) is increasing across Nigeria and threatens the effectiveness of long-lasting insecticidal nets (LLINs) and other pyrethroid-based interventions across Nigeria. This study quantified resistance levels, intensity, and metabolic contributions in An. gambiae s.l. populations across ecologically distinct zones of Oyo State, southwestern Nigeria, to generate evidence for locally tailored vector control strategies. METHODS Between May and September 2018, immature stages of Anopheles gambiae sensu lato were collected from six Local Government Areas in Oyo State, Nigeria, with 10-15 larval habitats sampled per LGA using standard dipping procedures. Specimens were reared to adulthood under controlled insectary conditions (27 ± 2 °C; 75-84% Relative Humidity) before testing. For each insecticide in each LGA, approximately 450-550 non-blood-fed female mosquitoes were evaluated in accordance with WHO testing procedures. Susceptibility to alpha-cypermethrin (12.5 μg/bottle), deltamethrin (12.5 μg/bottle), and permethrin (21.5 μg/bottle) was determined using the CDC bottle bioassay at diagnostic concentrations (1×), with standard replicate batches per assay. Populations exhibiting resistance at 1× were further examined using elevated concentrations (2×, 5×, and 10×) to quantify resistance intensity. The involvement of metabolic detoxification was assessed through the contribution of cytochrome P450-mediated resistance mechanisms. RESULTS A total of 9000 female mosquitoes were exposed to WHO diagnostic (1×) and elevated (2 × -10×) concentrations of alpha-cypermethrin, deltamethrin, and permethrin, complemented with piperonyl butoxide (PBO) synergist assays. At diagnostic dose, resistance was widespread, with mortality ranging from 5% (Egbeda) to 65% (Akinyele) for permethrin, 38.8-97% for alpha-cypermethrin, and 23-78% for deltamethrin, indicating significant spatial heterogeneity. Permethrin exhibited the highest resistance intensity, with incomplete mortality recovery even at 10×, while alpha-cypermethrin and deltamethrin showed full susceptibility restoration at 5× and 2×, respectively. Statistical analysis confirmed significant variation among LGAs (χ2, P < 0.001). Knockdown responses were reduced in Atiba, Afijio, and Egbeda, where several populations failed to reach 95% knockdown within 60 min. PBO pre-exposure fully restored susceptibility to alpha-cypermethrin (100%) across resistant LGAs, while deltamethrin showed partial recovery. In contrast, permethrin mortality remained incomplete (47-94%) after PBO, indicating limited metabolic involvement and likely target-site resistance. CONCLUSIONS Overall, the findings demonstrate intense, spatially heterogeneous pyrethroid resistance driven by multiple mechanisms, with important implications for malaria vector control. While PBO-based LLINs may provide partial mitigation, they are unlikely to fully address the complexity of resistance observed across the study area. Consequently, sustained control in Oyo State will require complementary and alternative strategies, including next-generation dual-active-ingredient nets and other non-pyrethroid interventions.