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

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.

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

SEASONAL INCIDENCE, FIELD SCREENING OF LOCAL LANDRACES, AND BIOCHEMICAL BASIS OF RESISTANCE IN RICE AGAINST PADDY EARHEAD BUG, LEPTOCORISA ORATORIUS (FABRICIUS) (HEMIPTERA: ALYDIDAE)

The paddy earhead bug, Leptocorisa oratorius (Fabricius) (Hemiptera: Alydidae), is a chronically destructive pest of rice (Oryza sativa L.) in India, with documented yield losses of 15–30% under moderate infestation and up to 80% under severe epidemics. A comprehensive investigation integrating seasonal population dynamics, large-scale varietal screening, and biochemical resistance characterisation was conducted at the College of Agriculture, V.C. Farm, Mandya, Karnataka, during Kharif 2021. Seasonal incidence studies recorded a peak population of 7.63 bugs/10 hills on the susceptible check Jaya during the last week of November, coinciding with the milky grain stage, and a substantially lower peak of 1.53 bugs/10 hills on IR 64. Pearson's correlation analysis identified maximum temperature as exerting a significant negative influence on bug density (r = −0.78** on Jaya; r = −0.67** on IR 64), while afternoon relative humidity (r = +0.72**; +0.68**) and sunshine hours (r = +0.69**; +0.72**) were significantly positive predictors, providing a meteorological basis for pest forewarning. Field screening of 50 local landraces categorised 15 as Resistant (R), 10 as Moderately Resistant (MR), 20 as Moderately Susceptible (MS), 3 as Susceptible (S), and 2 as Highly Susceptible (HS). Screening of 37 Advanced Varietal Trial (AVT) genotypes yielded 4 R, 11 MR, 14 MS, 5 S, and 3 HS entries. Biochemical analysis of 18 representative genotypes at the milky grain stage revealed that resistant accessions were characterized by elevated levels of total phenols (up to 1.49 mg g⁻¹), tannins (up to 4.85 mg g⁻¹), total free amino acids (TFA; up to 10.78 mg g⁻¹), and potassium (K; up to 3.54%) — all significantly and negatively correlated with grain damage (r = −0.86**, −0.94**, −0.95**, −0.93**, respectively). Susceptible genotypes accumulated higher total soluble sugars (TSS), total reducing sugars (TRS), crude proteins, nitrogen (N), and phosphorus (P), all of which showed highly significant positive correlations with grain damage (r = +0.95**, +0.97**, +0.98**, +0.95**, +0.87**, respectively). The resistant landraces Kave kantak, Nagland paddy, and Narali, alongside their distinctive biochemical profiles, provide a robust scientific foundation for developing durable pest-resistant rice cultivars and implementing ecologically rational integrated pest management programmes.

Phenotypic Resistance to Public Health Insecticides in Field Populations of the Bed Bug, Cimex lectularius L. (Hemiptera: Cimicidae), from Kwara State, Nigeria

Insecticide resistance and target-site mutations in field populations of Tuta absoluta in China.

The tomato leafminer, Tuta absoluta, poses a severe threat to tomato production in China, yet regional resistance patterns remain poorly characterized. This study investigates the insecticide resistance status and underlying molecular mechanisms in field populations of T. absoluta across major tomato-producing regions in China. Ten populations were evaluated for susceptibility to seven commonly used insecticides using standardized bioassays, alongside screening for resistance-associated target-site mutations in key genes. The results indicate that most populations remain susceptible to spinetoram, abamectin, and indoxacarb, supporting their continued effectiveness in field control. However, moderate resistance to emamectin benzoate was detected in several populations, with resistance ratios reaching up to 75.09 fold. Additionally, low to moderate resistance to Bacillus thuringiensis (Bt) and broflanilide was observed in certain regions. Although resistance ratios to bifenthrin were relatively low, consistently high LC50 values suggest a widespread reduction in baseline susceptibility. Molecular analyses revealed that the L1014F mutation in the voltage-gated sodium channel (VGSC) gene was fixed across all populations, while M918T and T929I mutations occurred at high frequencies. Notably, no significant correlation was found between these mutations and phenotypic resistance levels, and no resistance-associated mutations were detected in the nAChR gene. These findings highlight the complex and potentially multifactorial nature of resistance in Chinese T. absoluta populations and provide important guidance for optimizing insecticide rotation and resistance management strategies.

Insecticide Susceptibility and Toxicity against Pink Bollworm (Pectinophora gossypiella Saunders) Populations in Cotton

A laboratory study was conducted to evaluate the susceptibility of field populations of the pink bollworm, Pectinophora gossypiella (Saunders), collected from five major cotton-growing tehsils of Bharuch district, Gujarat, during the kharif seasons of 2024-25 and 2025-26. Populations from Amod, Bharuch, Jambusar, Netrang and Valia were tested against seven commonly used insecticides using a diet incorporation bioassay, with a susceptible Surat population as the reference. Larval mortality was assessed across seven concentrations, and LD₅₀-based toxicity indices were used to compare population susceptibility and relative insecticidal toxicity. Mortality increased with increasing insecticide dose across the tested populations. Across insecticides, the highest cumulative mortality in the field populations ranged from 81.25 to 98.65% in Netrang, 82.34 to 93.06% in Bharuch, 67.56 to 90.28% in Amod, 65.45 to 80.38% in Jambusar and 63.70 to 79.73% in Valia. Toxicity-index analysis indicated comparatively greater susceptibility in the Netrang population for most insecticides, whereas Valia and Jambusar generally showed lower susceptibility. Among the tested insecticides, emamectin benzoate, indoxacarb, lambda-cyhalothrin and spinosad showed comparatively higher toxicity, while profenofos and chlorpyrifos were relatively less effective. The observed spatial variation in susceptibility supports the value of location-specific monitoring for insecticide selection and resistance-management planning in cotton. The results provide a laboratory-based comparison of local population susceptibility profiles.