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Lepidoptera is the second most diverse insect order outnumbered only by the Coeleptera. Acetylcholinesterase (AChE) is the major target site for insecticides. Extensive use of insecticides, to inhibit the function of this enzyme, have resulted in the development of insecticide resistance. Complete knowledge of the target proteins is very important to know the cause of resistance. Computational annotation of insect acetylcholinesterase can be helpful for the characterization of this important protein. Acetylcholinesterase of fourteen lepidopteran insect pest species was annotated by using different bioinformatics tools. AChE in all the species was hydrophilic and thermostable. All the species showed lower values for instability index except L. orbonalis, S. exigua and T. absoluta. Highest percentage of Arg, Asp, Asn, Gln and Cys were recorded in P. rapae. High percentage of Cys and Gln might be reason for insecticide resistance development in P. rapae. Phylogenetic analysis revealed the AChE in T. absoluta, L. orbonalis and S. exigua are closely related and emerged from same primary branch. Three functional motifs were predicted in eleven species while only two were found in L. orbonalis, S. exigua and T. absoluta. AChE in eleven species followed secretory pathway and have signal peptides. No signal peptides were predicted for S. exigua, L. orbonalis and T. absoluta and follow non secretory pathway. Arginine methylation and cysteine palmotylation was found in all species except S. exigua, L. orbonalis and T. absoluta. Glycosylphosphatidylinositol (GPI) anchor was predicted in only nine species.

Fruit flies have a great influence on fruit and vegetable industry of Pakistan. Bactrocera dorsalis Hendel (Tephritidae) is a polyphagous pest in large number of fruit and vegetable crops worldwide. Virulence of 4 entomopathogenic nematodes (EPNs) species, Heterorhabditis bacteriophora, H. indica, Steinernema carpocapsae, and S. asiaticum, was evaluated at different temperature degrees (15, 20, 25, 30 and 35 °C) against the immature stages of fruit fly species, B. dorsalis. The tested EPNs species showed a temperature dependent virulence against the fruit fly immatures. All EPNs showed a poor infectivity at the lowest temperature (15 °C) and a high infectivity at the highest temperature (35 °C). In overall, H. bacteriophora performed the best against the fruit fly larvae and pupae at all temperature degrees. At 35 °C, all the EPNs caused more than 95% mortality in fruit fly maggots, but H. bacteriophora and S. carpocapsae performed better than the others. The EPNs infectivity increased with increasing the temperature and exposure time. Similar results were recorded in case of pupae. H. bacteriophora and S. carpocapsae caused more than 70% pupal mortality rates at 35 °C.

The predatory efficacy of phytoseiid mites, Neoseiulus barkeri was evaluated against onion thrips in controlled conditions. Different larval instars and adult thrips were provided as prey in different combinations (choice) or separately (no-choice). In choice test, no significant difference was observed in total thrips consumption per day. But in both observation hours (12 h or 24 h), a significant difference was observed between the feeding of immature and adult thrips. In a no-choice test,when we confined N. barkeri to feed on a specified diet of T. tabaci (first instar, second instar, or adults separately), a significant difference in total thrips consumption per day was observed in each prey group. In both tests, predatory mites fed more on first larval instar thrips compared to second larval instar and adults. However, consumption rate was rather higher during initial feeding hours (12 h) and slowed down later (24 h); this may be due to aggressive predation initially. The findings suggest that N. barkeri feed more on younger instars of T. tabaci and if these predators are released during early pest outbreak it will control the thrips population.

RNA interference (RNAi) of vital insect genes is a potential tool for targeted pest control. However, selection of the right target genes is a challenge because the RNAi efficacy is known to vary among insect species. Cotton mealybug, Phenacoccus solenopsis, is a phloem-feeding economically important crop pest. We evaluated the RNAi of 2 vital genes, Bursicon (PsBur) and V-ATPase (PsV-ATPase) as potential targets in P. solenopsis for its control. PCR fragments of PsBur and PsV-ATPase were amplified using cDNA synthesized from the total RNA. The PCR amplicons were cloned into Potato virus X (PVX) to develop recombinant PVX for the inoculation of Nicotiana tabacum plants for bioassays with healthy P. solenopsis. Reverse-transcription-polymerase chain reaction (RT-PCR) was used to validate the expression of transgenes in the recombinant-PVX-inoculated plants (treated), and suppression of the target genes in the mealybugs exposed to them. The RT-PCR confirmed the expression of transgenes in the treated plants. Mealybug individuals on treated plants either died or showed physical deformities. Further, the population of mealybug was significantly reduced by feeding on N. tabacum expressing RNAi triggers against PsBur and PsV-ATPase. The results conclude that RNAi is activated in P. solenopsis by feeding on N. tabacum expressing RNAi triggering elements of PsBur and PsV-ATPase genes through recombinant PVX vector. Further, V-ATPase and Bursicon genes are potential targets for RNAi-mediated control of P. solenopsis.

To curb the increasing demand for nitrogenous fertilizers, it is imperative to develop new cultivars with comparatively greater nitrogen use efficiency (NUE). Nonetheless, so far very meager information is available concerning the variances among barley (Hordeum vulgare L.) varieties for their response to nitrogen deprivation. The current study was carried out to explore the potential of barley genotypes for higher NUE. A hydroponic experiment was conducted at seedling stage to compare the performance of four barley genotypes, ZD9 and XZ149 (with higher NUE) and HXRL and XZ56 (with lower NUE) in response to low (0.1 mM) and normal nitrogen (2 mM) levels. Under low N, all the genotypes expressed less number of tillers, decreased soluble proteins, chlorophyll and N concentrations in both roots and shoots, in comparison with normal N supply. However, significant differences were found among the genotypes. The genotypes with high NUE (ZD9 and XZ149) showed higher N concentration, increased number of tillers, improved chlorophyll and soluble proteins in both roots and shoots as compared to the inefficient ones (HXRL and XZ56). Furthermore, nitrate transporter gene (NRT2.1) showed higher expression under low N, both in roots and leaves of N efficient genotypes, as compared to the N inefficient ones. However, N assimilatory genes (GS1 and GS2) showed higher expression under normal and low N level, in leaves and roots respectively. The outcome of the study revealed that genotypes with higher NUE (ZD9 and XZ149) performed better under reduced N supply, and may require relatively less N fertilizer for normal growth and development, as compared to those with lower NUE. The study also revealed a time-specific expression pattern of studied genes, indicating the duration of low N stress. The current study suggested that future work must involve the time course as a key factor while studying expression patterns of these genes to better understand the genetic basis of low-N tolerance.

Two-year field experiments were conducted to investigate the phytotoxicity of mesquite (Prosopis juliflora) on weed control and yield of wheat in 2013-14 and 2014-15. Mesquite aqueous extracts were prepared with 10, 20, 30 and 40% concentration of leaves, stems, and roots and were compared with tap water (control). These experiments were laid out in a completely randomized block design with four replications. All parameters (weed density, fresh weed biomass, dry weed biomass, chlorophyll content, leaf area index, leaf area duration, crop growth rate, net assimilation rate, plant height and number of tillers) were significantly reduced by applying the mesquite extracts. Among different concentrations, the maximum level (40%) of all three plant parts of mesquite subsequently reduced the study parameters including weed density, fresh and dry weed biomass, leaf area index, leaf area duration, crop growth rate, net assimilation rate, chlorophyll contents, plant height, number of tillers, spike length, number of grains, 1000-grain weight, grain yield, biological yield, harvest index and grain protein content. On the basis of the results, it is concluded that aqueous extracts of mesquite may contain many phytotoxic substances which can negatively affect the growth and yield of agricultural crops; therefore, wheat should not be planted close to mesquite. RESUMO: Experimentos de campo foram conduzidos durante dois anos para investigar a fitotoxicidade da algaroba (Prosopis juliflora) no controle de plantas daninhas e no rendimento do trigo nos períodos de 2013-14 e 2014-15. Foram preparados extratos aquosos de folhas, caules e raízes de algaroba com concentração de 10, 20, 30 e 40%, os quais foram comparados com água corrente (controle). Utilizou-se o delineamento em blocos completamente casualizados com quatro repetições. Todos os parâmetros (densidade de plantas daninhas, biomassa fresca das plantas daninhas, biomassa seca das plantas daninhas, teor de clorofila, índice de área foliar, duração de área foliar, taxa de crescimento da cultura, taxa de assimilação líquida, altura da planta e número de perfilhos) sofreram redução significativa pela aplicação dos extratos de algaroba. Entre as diferentes concentrações, o nível máximo (40%) das três partes das plantas da algaroba reduziu os parâmetros do estudo, incluindo densidade das plantas daninhas, biomassa fresca e seca das plantas daninhas, índice de área foliar, duração da área foliar, taxa de crescimento da cultura, taxa de assimilação líquida, teores de clorofila, altura das plantas, número de perfilhos, comprimento da espiga, número de grãos, peso de mil grãos, rendimento de grãos, rendimento biológico, índice de colheita e teor de proteína do grão. Com base nos resultados, conclui-se que os extratos aquosos da algaroba são capazes de conter muitas substâncias fitotóxicas que podem exercer efeito negativo no crescimento e no rendimento das culturas agrícolas. Por essa razão, o trigo não deve ser plantado perto da algaroba.

The aim of the study was to determine insecticidal potential of three plant extracts (Calatropis procera, Eucalyptus globulus and Mentha arvensis) and crude venom of an orb-web spider, Neoscona theisi, in the laboratory using Musca domestica and Aedes aegypti as model insects. Laboratory bioassays were conducted against three doses of plants extracts (0.2 mg/ml, 0.4 mg/ml and 0.6 mg/ml) and spider venom (10 µg/ml, 20 µg/ml and 30 µg/ml). Ellman et al.'s (1961) method was followed to estimate the activity of acetylcholinesterase of insects. Calatropis procera was found to be more effective in killing the insects. The mortality rate was increased with an increase in plant extract or venom dose. Calatropis procera inhibited acetylcholinesterase more proficiently as compared to the M. arvensis and E. globulus extracts. Crude spider venom also significantly inhibited the estimated activity of acetylcholinesterase in M. domestica and Ae. aegypti. It is concluded from the study that both plant extracts and spider venom inhibited the activity of acetylcholinesterase in M. domestica and Ae. aegypti but C. procera is more efficient in killing the insects.

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is an economically important pest of citrus because it serves as a vector of the causal pathogens of huanglongbing (HLB) also known as citrus greening disease. The increased use of insecticides for control of D. citri negatively impacts several natural enemies including some effective ladybeetle species which are not available commercially. The two-spotted ladybeetle, Adalia bipunctata (Coleoptera: Coccinellidae) is found in some crop and forest ecosystems of Asia, Europe and North America and available commercially. It is known to attack aphids and mealybugs but there are no published records of feeding on psyllids. We evaluated suitability and preference of A. bipunctata for nymphs of D. citri compared to corn leaf aphid Rhopalosiphum maidis (Hemiptera: Aphididae) a global pest of cereal crops and prey for many predaceous insects. We also compared development and reproduction of A. bipunctata on these two species with frozen eggs of the Mediterranean flour moth Ephestia kuehniella (Lepidoptera: Pyralidae) at 25°C. Initially, more D. citri than R. maidis nymphs were consumed in the no-choice tests although final consumption by larva and adult of A. bipunctata did not differ in the choice and no-choice tests. Larval development was prolonged by one day on D. citri compared to R. maidis nymphs but did not differ between either of these diets and E. kuehniella. Larval survival to adult averaged 93–100% and was not impacted by diet. Adult life span did not differ between diets although those on D. citri and R. maidis nymphs weighed less and produced fewer but more fertile eggs than on E. kuehniella eggs. Significant reduction of D. citri nymphs averaging 54% was observed in colonies caged with adult A. bipunctata on field planted citrus. R° (net reproductive rate) was least for beetles fed R. maidis, but otherwise there were no significant differences in demographic parameters. Successful feeding, development and reproductive performance of A. bipunctata suggest its usefulness as biological control agent of D. citri as well as aphid species exemplified by R. maidis.