Realized heritability of resistance to deltamethrin in a field strain of Musca domestica Linnaeus (Diptera: Muscidae)

Baseline of susceptibility, risk assessment, biochemical mechanism, and fitness cost of resistance to dimpropyridaz, a novel pyridazine pyrazolecarboxamide insecticide, in Bemisia tabaci from China

Bemisia tabaci is one of the most destructive agricultural insect pests around the world, and it has developed high levels of resistance to most pesticides. Dimpropyridaz, a novel insecticide developed by BASF, displays excellent activity against piercing-sucking insect pests. In this study, baseline of susceptibility showed all tested field populations of B. tabaci are susceptible to dimpropyridaz. After continuous selection with dimpropyridaz in the lab, a B. tabaci strain (F12) developed 2.2-fold higher level of resistance compared with a susceptible MED-S strain, and the realized heritability (h2) was estimated as 0.0518. The F12 strain displayed little cross-resistance to afidopyropen, cyantraniliprole, sulfoxaflor, or abamectin, and significantly increased activity of cytochrome P450 monooxygenase (P450). The fitness cost of dimpropyridaz resistance was evident in F12 strain, which had a relative fitness of 0.95 and significantly lower fecundity per female compared with MED-S strain. Taken together, B. tabaci displays high susceptibility to dimpropyridaz in the field, and low risk of developing resistance to dimpropyridaz under successive selection pressure. Little cross-resistance to popular insecticides was found, and fitness cost associated dimpropyridaz resistance was observed. Higher activity of cytochrome P450 in the F12 strain, may be involved in the process of detoxifying dimpropyridaz in whitefly.

Pyriproxyfen induces lethal and sublethal effects on biological traits and demographic growth parameters in Musca domestica

Musca domestica is a global insect-pest of human beings and animal agriculture. Pyriproxyfen, a juvenile hormone analog, has shown its potential for effective management of M. domestica. However, lethal and sublethal effects of pyriproxyfen on biological traits and demographic growth parameters of M. domestica are still unknown. The present study investigated the effects of lethal and sublethal concentrations on different biological traits of M. domestica for two generations i.e., exposed parents (F0) and their offspring (F1). Concentration-response bioassays revealed that concentrations of pyriproxyfen that caused 50% (LC₅₀), 25% (LC₂₅), 10% (LC₁₀) and 2% (LC₂) mortality of M. domestica were estimated as 0.12, 0.06, 0.03 and 0.01 μg/g, respectively. In the F0 generation, exposure of 3^rd instar larvae to these concentrations resulted in a reduced pupation rate, lengthened pupal stage duration, light weight pupae and reduction in adult emergence in a concentration-dependent manner. In the case of F1 generation, similar trend was observed for pupation rate, pupal stage duration, and total developmental period (i.e., egg to adult); however, pupal weight was affected at LC₁₀, LC₂₅, LC₅₀ levels, and adult emergence at only LC₂₅ and LC₅₀ levels. The values of demographic growth parameters, analyzed through age-stage, two-sex life table theory, were significantly decreased at all the levels of pyriproxyfen compared with control. This study highlights that pyriproxyfen has the potential to suppress the population of M. domestica through its lethal and sublethal effects and presents an empirical basis from which to consider management decisions for chemical control in the field.

Side effects of insecticidal usage in rice farming system on the non-target house fly Musca domestica in Punjab, Pakistan

Insecticidal usage in the rice farming system may affect non-target insect species present in the same fields. Musca domestica, a well-known pest of medical and veterinary importance worldwide, is one of the important non-target insect species present in the rice farming system. In this study, five strains of M. domestica were exclusively collected from rice fields in major rice cultivated areas of Punjab, Pakistan, and evaluated for the presence of insecticide resistance against nine commonly used insecticides in the rice farming system. Moreover, the performance of life-history traits was also studied. Compared with a Lab-susceptible reference strain of M. domestica, all the field strains exhibited moderate levels of resistance to carbofuran (RRs = 27.96-46.00 fold) and cartap hydrochloride (RRs = 31.48-48.21 fold), low to moderate levels of resistance to gamma-cyhalothrin (RRs = 19.00-43.00 fold), chlorantraniliprole (RRs = 11.90-27.10 fold), monomehypo (RRs = 14.38-25.84 fold), and fipronil (RRs = 13.23-40.15 fold), low levels of resistance to triazophos (RRs = 11.13-19.83 fold), and very low to low levels of resistance (RRs = 7.83-13.28 fold) to flonicamid. The performance of life-history traits (developmental time, adult eclosion rate, fecundity, egg hatch rate, and longevity of adults) of field strains was weaker as compared with that of the Lab-susceptible strain. These results contribute to the growing knowledge on the effects of insecticidal usage in agriculture on non-target invertebrates, and necessitate the need to explore alternate insecticides that can effectively control insect pests but safe for non-target organisms.