Ayesha Iftikhar

Aphids are among the most destructive insect pests of wheat, with their population dynamics strongly influenced by host genotype, sowing time, and prevailing environmental conditions. This study evaluated aphid infestation across seven sowing dates and 12 wheat genotypes, evaluating relationship with natural enemies and weather factors with a goal of identifying sowing dates and genotypes associated with low aphid density. Seasonal mean aphid density differed significantly among genotypes for each sowing date. Of the 12 genotypes of wheat studied, two were highly susceptible and two consistently showed lower infestation. Aphid outbreaks peaked between 14 and 27 February, with maximum populations recorded on 20 and 27 February across several genotypes. Natural enemies such as Coccinellids, Chrysopids, Syrphids , and parasitoids displayed significant positive associations with aphid abundance, suggesting they are able to track cues to find prey, and may play a regulatory role. Abiotic factors were strongly predictive of infestation: averaging across all genotypes of wheat, aphid abundance decreased with temperature, with temperature alone explaining 73.5% of the variation in abundance. Aphid abundance also decreased with hours of daylight (explaining an additional 14.1% of the variation in abundance). These findings demonstrate that aphid population dynamics in wheat are genotype-specific and environmentally driven, with mid-to-late February identified as the most critical infestation window. Selecting resistant/tolerant genotypes, adjusting sowing dates, and leveraging the role of natural enemies provide a sustainable pathway for aphid management. These insights are vital for refining integrated pest management strategies under changing climatic conditions.

Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) represents a major threat to maize production across Pakistan, with chemical control serving as the predominant management approach. The intensive application of insecticides, particularly diamide compounds such as chlorantraniliprole, has escalated concerns regarding resistance evolution in field populations. This study evaluated the insecticidal efficacy of seven commonly used compounds against geographically diverse field-collected populations of S. frugiperda from major maize-growing regions of Pakistan, revealing significant inter-population variability in susceptibility profiles. Chlorantraniliprole was selected for comprehensive transgenerational screening based on moderate baseline LC₅₀ values and optimal laboratory colony establishment parameters. A representative field strain underwent six consecutive generations of selection pressure at LC₇₀ concentrations, resulting in a 4.48-fold increase in resistance levels with a realized heritability (h²) of 0.198. Predictive modeling using established quantitative genetic frameworks demonstrated that resistance evolution rates are critically dependent on both selection intensity and genetic parameters. Under constant h² = 0.198, increasing selection intensity substantially accelerated resistance development, with 10-fold resistance achievable in approximately 18 generations at 80% selection intensity (slope = 2.696) compared to 36 generations at lower intensities (slope = 4.696). Sensitivity analysis revealed that heritability variations from 0.148 to 0.248 could reduce generation requirements from >40 to ~25 generations when slope was maintained at 3.696. Life table analyses of the chlorantraniliprole-selected strain demonstrated significant fitness costs manifested as extended developmental periods, reduced reproductive output, and decreased intrinsic rate of population increase (r), indicating evolutionary trade-offs associated with resistance acquisition. These findings provide crucial insights for developing sustainable management strategies, highlighting the importance of integrating resistance monitoring, refuge-based approaches, and rotation with insecticides of different modes of action to delay resistance buildup in field populations. Such data-driven management frameworks are vital for maintaining the long-term efficacy of diamides in Pakistan’s maize production systems.

Fall armyworm (FAW) Spodoptera frugiperda, is a serious invasive pest of many crops that causes huge economic losses to agricultural commodities. Insecticides are employed for the management of S. frugiperda. In this study, we investigated the impact of sublethal concentration (LC₁₀) and low lethal concentration (LC₃₀) of spinetoram and emamectin benzoate on S. frugiperda using two-sex life table method. Bioassay results revealed that emamectin benzoate exhibited more toxicity on the 3rd instar of S. frugiperda (LC₅₀ 8.35 × 10⁻⁴ mgL⁻¹) than spinetoram (LC₅₀ 2.6 × 10⁻² mgL⁻¹) after 48 h exposure. The total longevity, adult pre-ovipositional period (APOP) and total pre-ovipositional period (TPOP) were prolonged, while pre-adult survival rate and fecundity were reduced at both concentrations of spinetoram and emamectin benzoate. Moreover, the key demographic parameters, including the intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R₀), were significantly lower in insecticide treated groups as compared to untreated insects. Our findings revealed that the sublethal and low lethal concentrations of both insecticides reduce the survival and reproductive capability of S. frugiperda. These results would be useful to assess the overall effect of both insecticides on S. frugiperda and can provide important implications for the rational utilization of insecticides against S. frugiperda.

Background: Coronavirus disease 2019 (Covid-19), declared as a pandemic in March 2020, is an acute respiratory tract illness caused by coronavirus 2 (SARS-CoV2) with clinical manifestations ranging from mild upper respiratory tract symptoms to severe pneumonia. Objectives: To determine the disease spectrum of Covid-19 in a cohort with a travel history from Iran. Materials & Methods: This cross-sectional study with a retrospective collection of data was conducted at Agha Khan University, Karachi from 15th March to 19th April 2020. One hundred and fifty-five laboratory-confirmed cases of Covid-19 were recruited from a government quarantine facility. Data were obtained from the Punjab Emergency Services (Rescue 1122) database where a record of SARS-CoV-2 positive cases and quarantined persons is maintained. Study subjects with a travel history to Iran were contacted by telephone to obtain information about demographics, symptoms, and co-morbid conditions. SPSS version 24 was used to analyze the data. Frequencies and percentages were calculated. Results: Among the returning travelers, 213 had laboratory-confirmed Covid-19, out of which 155 were included in this study. 56.1% were males with a mean age of 40 years. Among the study participants, 91.6% remained asymptomatic throughout the stay, while 8.4 % became symptomatic. 77.5% of the participants had received BCG vaccination in childhood. Among symptomatic cases 15.4% had asthma and 7.7% had hypertension. The most common clinical manifestation was cough which was present in 38.5% of the study participants. None died among the study participants. Conclusion: A mild presentation of COVID-19 was seen in our study participants with 91.6% among them being asymptomatic, while 8.4% were symptomatic. There was a high positivity rate in males as compared to females.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Insect predators, in general, play an important role in regulating pest populations in agricultural systems, but may be negatively affected by pesticides used in pest management. Convergent lady beetle, Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) is known as an important biological control agent of soft-bodied insect pests. The development of Integrated Pest Management (IPM) program against insect pests requires an assessment of the side effect of insecticides on biological control agents. In the present work, we assessed the sublethal effects of an insect growth regulator, Pyriproxyfen (juvenile hormone mimic) on a common aphidophagous beetle, H. convergens by computing its demographic parameters through age-stage, two-sex life table theory. Present results showed that sublethal (LC₁₀ and LC₃₀) concentrations of tested insecticide prolonged the pre-adult developmental duration while adult longevity, fecundity and fertility were reduced following treatment compared with control. However, total pre-ovipositional period (TPOP) was declined with the increasing trend of insecticide concentration. In additions, population growth parameters such as intrinsic rate of increase r, finite rate of increase λ and net reproductive rate R₀ were dramatically reduced in H. convergens population when they treated with sublethal concentrations pyriproxyfen. Therefore, the results obtained through this study reflected that pyriproxyfen impairs the population growth parameters and could reduce the biological services provided by H. convergens. Thus, more attention should be paid to the use of this insecticide in IPM program.

Background: The demographic parameters of the predacious seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera: Coccinellidae) reared on the following four host aphid species were compared: Rhopalosiphum padi Linnaeus (Hemiptera: Aphididae), Rhopalosiphum maidis Fitch (Hemiptera: Aphididae), Sitobion avenae Fabricius (Hemiptera: Aphididae), and Schizaphis graminum Rondani (Hemiptera: Aphididae). Methods: The developmental period, fecundity, adult preoviposition period, total preoviposition period and population parameters were evaluated based on the two-sex age-stage life table. The duration of the developmental stages and the population parameters were calculated with the TWOSEX-MSChart program, whereas population size was projected based on the two-sex age-stage life table data with the TIMING-MSChart program. Results: The intrinsic rate of increase (r) was the highest in the R. padi predators (0.1946 per day), followed by the S. graminum (0.1435 per day), S. avenae (0.1400 per day), and R. maidis (0.1180 per day) predators. The differences in the net reproductive rate (R₀) and the finite rate of increase (λ) when C. septempunctata was reared on the four aphid species were consistent with the r values. This trend was reversed for the mean generation time (T), which ranged from 29.02 days for the lady beetles reared on R. padi to 39.75 days for the lady beetles reared on R. maidis. Interestingly, R. padi was the most suitable host, while the congeneric R. maidis was the least suitable. The results of this study may be useful for future investigations regarding the ecological effects of predatory species and the mass-production of C. septempunctata in the laboratory for an augmentative release of an aphid predator.

Effect of Temperature on Demography and Predation Rate of Menochilus sexmaculatus (Coleoptera: Coccinellidae) Reared on Phenacoccus solenopsis (Hemiptera: Pseudococcidae)