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Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a global pest causing damage to several crops. However, its management using chemical control is a challenge due to its capacity to evolve resistance to insecticides. After 6 generations of selection with lambda-cyhalothrin, the LC50 for the insecticide-resistant strain (Lambda-Sel) was 486 ppm, higher than that of the field strain (FAW-MUL) (7.5 ppm), susceptible laboratory strain (Lab-PK) (0.46 ppm), and laboratory unselected strain (UNSEL) (5.26 ppm). Laboratory selection with lambda-cyhalothrin increased resistance from 16.3- to 1056.52-fold and 1.43- to 92.4-fold to lambda-cyhalothrin compared to Lab-PK and UNSEL strains, respectively. The selected strain of S. frugiperda (Lambda-Sel) presented low cross-resistance to chlorpyrifos, moderate to deltamethrin and indoxacarb, very low to spinosad, and no cross-resistance to emamectin benzoate. The realized heritability (h2) of lambda-cyhalothrin resistance in the Lambda-Sel strain was very high (0.88). The reciprocal cross progenies of F1 (Lambda-Sel ♀ × Lab-PK ♂), F1' (Lambda-Sel ♂ × Lab-PK ♀), BC1 (F1 ♀ × Lambda-Sel ♂), and BC2 (F1 ♀ × Lab-PK ♂) showed high resistance ratios of 545.64-, 396.52-, 181.18-, and 146.54-fold, respectively compared to Lab-PK. The degree of dominance values for lambda-cyhalothrin in F1 and F1' indicates incompletely dominant resistance. The difference between observed and expected mortality in backcross populations (BC1 and BC2) revealed a polygenic resistance. In conclusion, the resistance to lambda-cyhalothrin was autosomal, incompletely dominant, and polygenic. These findings provide new insights for insect resistance management strategies to mitigate the occurrence of resistance in this global pest., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Dusky cotton bug Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae) has been found to infesting cotton and other plants in Pakistan and some other countries. However, in Pakistan the increasing infestation of O. hyalinipennis was controlled with different insecticides, but some degree of resistance has been reported. Inheritance and cross-resistance of dimethoate resistance selection have not been documented in O. hyalinipennis previously. Therefore, this study for the first time characterized dimethoate resistance in O. hyalinipennis by inducing it in the laboratory for six generations. The selected population was 9.70- and 157-fold resistant compared with the field and laboratory population, respectively. The dimethoate resistance selection did not bring about any cross-resistance with lambda-cyhalothrin (1.47-fold) but had a very low cross-resistance with chlorfenapyr (3.03-fold) and acephate (2.21-fold) compared with the field population. The overlapping in 95% confidence limits of LC50 ratios of F1 (R♀ × S♂) and F1' (R♂ × S♀) indicated the lack of maternal effects, whereas their degree of dominance of 0.54 and 0.51 suggested an incompletely dominant resistance inheritance. Multiple factors were involved in dimethoate resistance as implied from Chi-square analyses of backcrosses. In conclusion, O. hyalinipennis develops easily resistance to dimethoate due to selection. Lack of/or very low cross-resistance with lambda-cyhalothrin, chlorfenapyr and acephate implies that these insecticides can be used in rotation. Moreover, dimethoate resistance inheritance was incompletely dominant, autosomal and polygenic which implies that resistance to dimethoate can be delayed by using it in rotations, alterations, mosaics and combinations. [ABSTRACT FROM AUTHOR]

The dusky cotton bug, Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae) is a serious pest of cotton and damages cotton seed by reducing the oil content. In Pakistan, O. hyalinipennis is managed by using various insecticides and has developed resistance to several insecticides. In this study, O. hyalinipennis was selected with bifenthrin for 12 generations (G 1 to G 12) and developed a 55.64-fold resistance when compared with an unselected population (Unsel Pop). Bifenthrin resistance declined from 55.64 to 24.93-fold when selected population was removed from bifenthrin selection pressure for four generations (G 13 to G 16). Bifenthrin selected (Bifen-Sel) population showed a very low cross-resistance to profenofos (2.82-fold), deltamethrin (2.35-fold) and acetamiprid (2.21-fold) when compared with a field population (Field Pop). The bifenthrin resistance was incomplelety dominanat and autosomal. The relative fitness (Rf) of Bifen-Sel population was 0.58 along with significant decreases in average nymphal survival, fecundity, egg hatchability, intrinsic rate of population increase (r m), net reproductive rate (Ro) and biotic potential (Bp). The Rf of Cross 1 and Cross 2 was 1.07 and 1.22, respectively. The high fitness costs, instable resistance and a very low cross-resistance with other insecticides might be useful in slowing down the evolution of bifenthrin resistance by implementing an insecticide rotation plan. Image 1 • Selection for 12 generations with bifenthrin induced 55.64-fold resistance in DCB. • Relaxing from selection pressure reverted bifenthrin resistance to 24.93-fold. • No obvious cross-resistances were observed with all tested insecticides. • Bifenthrin-selected population was low in fitness. • Bifenthrin resistance was incompletely dominant and autosomal. [ABSTRACT FROM AUTHOR]