Aphis Gossypii Research Articles

The toxicity, repellent, and biochemical effects of four wild plant extracts against Aphis gossypii Glover and Phenacoccus solenopsis Tinsley: HPLC analysis of phenolic compounds

The insecticidal and repellent activities of the four wild plant extracts: stinging nettle, Urtica dioica L., white henbane, Hyoscyamus albus L., camphorweeds, Pluchea dioscoridis L., and cocklebur, Xanthium strumarium L. were tested compared to the insecticide spirotetramat against the 3rd nymphal instar of Aphis gossypii Glover and adult females of Phenacoccus solenopsis Tinsley after 24 and 48 h of treatment. Their effects on acetylcholinesterase (AChE) and glutathione-S-transferase (GST) enzyme activities were also assessed to explore their possible mechanisms of action. The phenolic compounds of the plant extracts were investigated by high-performance liquid chromatography (HPLC) analysis. The most abundant compounds in the methanol extract from P. dioscoridis were gallic acid (14.45 µg/mL), and cinnamic acid (11.44 µg/mL); from U. dioica were caffeic acid (15.32 µg/mL) and syringic acid (13.47 µg/mL); from H. albus were syringic acid (7.12 µg/mL) and catechol (5.33 µg/mL); and from X. strumarium were p-coumaric acid (24.53 µg/mL) and pyrogallol (18.35 µg/mL). According to the LC50 values, the contact toxicity of U. dioica, H. albus, P. dioscoridis, and X. strumarium against A. gossypii was 40.3, 60.6, 56.2, and 32.3 mg/L, whereas, the contact toxicity against P. solenopsis was 56.4, 67.5, 64.3, and 36.2 mg/L, compared to the spirotetramat (17.2 and 24.5 mg/L), respectively, at 48 h of treatment. The highest repellency rates were observed with LC50 values for X. strumarium (63.2 and 60.3%), followed by U. dioica (46.2 and 43.5%), P. dioscoridis (45.3 and 42.8%), and H. albus extract (38.8 and 35.2%) compared to the spirotetramat (78.5 and 76.2%) against A. gossypii and P. solenopsis at 24 h, but decreased with time. The AChE and GST activities in pests were significantly inhibited, compared to control and spirotetramat, with dose and time-dependent effects. These findings indicate that tested wild extracts may be suggested as viable alternatives for aphids and mealybugs control.

Biological Parameters and Feeding Potential of Micromus timidus Hagen (Neuroptera: Hemerobiidae) on Selected Aphid Species

In the present study, we investigated on the developmental biology, adult longevity and fecundity of Micromus timidus Hagen on Aphis craccivora (Koch), Aphis gossypii Glover, Rhopalosiphum maidis (Fitch) and Uroleucon compositae (Theobald) at room temperature (28±20C) and relative humidity of 70%. The study design followed was completely randomized design (CRD). The study was conducted with three replications with 10 larvae in each replication for biology studies and for adult parameters 3 replications with 10 pairs in each replication used. Shortest incubation period, II instar and III instar duration, total larval period, pre-pupal period, and egg to adult period of M. timidus were recorded on A. craccivora, shortest I instar duration was recorded on U. compositae and least pupal period on A. gossypii. The developmental periods for all trait were extended when fed on R. maidis. The reproductive traits viz., oviposition period and adult longevity (male and female) were maximum when M. timidus adults fed on A. gossypii, and the highest fecundity was recorded when fed on A. craccivora. Feeding potential in M. timidus increases progressively across successive instars, with III instar larvae exhibiting the highest aphid predation rate, and first instar larvae displaying the lowest feeding activity. The maximum feeding potential of the larva was noted on A. craccivora (142.47 ± 31.66), while, the adult feeding potential increased when it was given with A. gossypii (1335.10 ± 192.74).

Thiacloprid-silica nano-delivery system enhances toxicity against Aphis gossypii and improves non-target biosafety

Nanotechnology aligns with the requirements of sustainable development of agriculture, and nano-pesticides offer a promising approach to controlling agricultural pests and increasing productivity. Non-target predators also play a crucial role in pest controls and enhancing the efficacy of pesticide on target organisms. Reducing the toxicity of pesticides to non-target organisms is key to of coordinating chemical control and biological control methods. Therefore, it is essential to assess the toxicity of nano-pesticides on non-target predators. In this study, a carbon dots-doped mesoporous silica nano-delivery system (Thi@CD-MSN) was successfully developed using CD-MSN as carrier material and thiacloprid (Thi) as a model pesticide. The results demonstrated that the synthesized Thi@CD-MSN exhibited a relatively high loading efficiency (33.58%). Laboratory bioassay experiments revealed that Thi@CD-MSN demonstrated effective insecticidal activity (LC50 = 21.67 mg/L) in controlling Aphis gossypii Glover. Besides, the acute toxicity of Thi@CD-MSN on Chrysoperla pallens larvae was significantly lower than that of Thi, as was its toxicity to 4T1 cells. These findings suggest that CD-MSN can serve as an ecological safety carrier for pesticide delivery, improving the effective utilization of Thi while reducing the risks to non-target predators. These results are essential for comprehending the effects of nano-pesticides on non-target predators, providing informative data for implementing biological and chemical control strategies. It strengthens the safety evaluation of nano-pesticides.

Population Dynamic of Aphis gossypii, and Their Parasitoids, and Effect of Some Insecticides on Aphids, Chlorophyll Content, Non-Enzymatic and Antioxidant Enzymes Activity in Cantaloupe Leaves in Greenhouses

Under green house, the Population density of Aphis gossypii on cantaloupe plants recorded two peaks on May 9th and 23th with 1409 and 1561 individuals/ 10 leaves in season 2022, while one highest peak, on 16th May with 1650 individuals/ 10 leaves in season 2023. Parasitism status of Aphidius colemani and Lysiphlebus fabarum varied from 1.49% on 25 April to 35.79% on 9th of May with seasonal parasitism 2023 in 2022 and ranged between 0.73% on 25th of April and 30.06% on 16th of May with seasonal parasitism 16.57% in 2023. Acetamiprid, imidacloprid, imidacloprid + abamectin, jojoba oil, orange oil and thiamethoxam + abamectin compounds were tested to control aphids during two seasons. Imidacloprid recorded the highest reduction with all average 97.88 ±1.15 and 97.39 ±1.15 in the first and second season respectively. the highest mean reduction of emergence of the two-parasites caused by thiamethoxam + abamectin by 16.92% followed by Imidacloprid with 16.87%. While the least toxicity to emergence of the parasitoids recorded with jojoba oil 0.0% followed by orange oil 1.93% in season 2022, while in season 2023, the higher parasitoid reduction caused by acetamiprid 18.05% followed by Imidacloprid 17.69% and thiamethoxam + abamectin 17.53%. Chlorophyll content increased with treatment jojoba oil followed by Imidacloprid by 47.91 and 44.73 unit in the first season and Thiamethoxam with abamectin lead to the highest content by 44.05 unit in the leaves followed by jojoba oil with 43.65 unit. The least treatment was Imidacloprid + abamectin with 39.55 unit compared with control treatment 40.43 unit. Treatment Thiamethoxam + abamectin recorded the highest content of carbohydrates (48.43) compared with control (47.71). Treatments of insecticides led to increase of protein, fats and total lipid compared with control. Also, Antioxidant enzymes activity in cantaloupe leaves were found to be increased in the treatment of insecticides compared with control.

Occurrence, distribution and description of Harmonia dimidiata (Fabricius), a predacious Coccinellid from West Bengal, India

Aim: To provide information about the occurrence and distribution of Harmonia dimidiata from West Bengal and facilitate the identification of species based on morpho-taxonomy. Methodology: Survey was done in different agro-climatic zones of West Bengal. Specimens were procured from their associated host plants, brought to the laboratory and investigated for taxonomic characters. Results: The morpho-taxonomy of H. dimidiata, as well as its host record, and distribution, were fully explained in the present investigation. It is most common in hill, terai, and old alluvial zone of West Bengal. They have been observed preying on Rhopalosiphum maidis (Fitch) in corn and Aphis gossypii (Glover). Interpretation: H. dimidiata population were recorded during survey from four different agro-climatic zones of West Bengal. They were observed to be preyed upon A. gossypii and R. maidis. The information about the biodiversity of H. dimidiata and their role as predator of numerous agriculturally important crop pests are extremely valuable that enrich our knowledge and immensely help in devising a pest management programme considering them as an important biocontrol agent. Furthermore, research on their biodiversity aids in learning about the predaceous behaviour in connection with the pest and crop populations, their reproduction and occurrence. This information is indeed praiseworthy while exploiting the ladybird species, H. dimidiata for a commercial biocontrol operation. Key words: Coleoptera, Coccinellidae, Harmonia dimidiata, Predaceous, West Bengal

Effects of saline-alkali stress on cotton growth and physiochemical expression with cascading effects on aphid abundance.

Environmental stresses, such as soil salinity or alkalinity, usually affect crop growth and secondary plant metabolism, with follow on effects on foliar-feeding insects. Nevertheless, the underlying mechanism of how saline-alkali stress affects the key cotton pest Aphis gossypii Glover is poorly understood. In this study, we first considered effects of three types of saline-alkali stress (i.e., salinity alone, alkalinity alone - both at different concentration - and their mixed effects) on cotton plants. We then measured impacts of stress on (1) above and below plant growth traits (e.g., plant height, leaf area, root volume), (2) levels of nutrients and secondary metabolites in cotton leaves, and (3) feeding behavior, life-table parameters, and population growth of A. gossypii. We then used a path analysis to evaluate cascading effects of changes in plant growth (due to stress) and changes in levels of nutrients or secondary metabolites on growth of individual cotton aphids and aphid populations. We found either salinity or alkalinity stresses significantly reduced cotton growth, increased the content of tannin, soluble sugars, and proline in the leaves, and suppressed aphid growth and development, (including longevity, fecundity, and intrinsic rate of increase) and aphid population growth. Alkalinity had stronger effects on these traits than did salinity. This work provides insights into the bottom-up interaction mechanism by which these environmental stresses mediate aphid infestation levels in the cotton agricultural ecosystem.

The effect of four botanical volatile oil against aphid (Aphis gossypii) and mealybug pests (Phenacoccus solenopsis). A toxicological and chemical composition study

Given the economic damage caused by cotton mealybugs Phenacoccus solenopsis, (P. solenopsis) and aphids Aphis gossypii (A. gossypii), it was a need to look for more acceptable and safe materials. Four local plant extracts were assessed Ocimum basilicum, Origanum majorana, Pipper nigrum, and Schinus terebinthifolius represented by their volatile oils, against these two pests in the laboratory, with the following LC50 values for each applied volatile oil extract against aphid and mealybug 1938.05, 7391.33, 674.81, 5548.65, 644.45, 4383.52, 727.88, and 6735.62 ppm using the four previous extracts respectively. The highest mortality percentage was 50.0 and 49.3% for pipper nigrum, while the lowest percentage was for O. basilicum with 36.2 and 31.2% against P. solenopsis and A. gossypii, respectively. The oils that gave the highest mortality percentages pipper nigrum and Origanum majorana were analyzed using GCMS technique revealed the existence of major compounds belonging to the terpenoids chemical group, which have a noticeable role in the process of controlling these pests.

Natural variation at the cotton HIC locus increases trichome density and enhances resistance to aphids.

Plant trichomes are an excellent model for studying cell differentiation and development, providing crucial defenses against biotic and abiotic stresses. There is a well-established inverse relationship between trichome density and aphid prevalence, indicating that higher trichome density leads to reduced aphid infestations. Here we present the cloning and characterization of a dominant quantitative trait locus, HIC (hirsute cotton), which significantly enhances cotton trichome density. This enhancement leads to markedly improved resistance against cotton aphids. The HIC encodes an HD-ZIP IV transcriptional activator, crucial for trichome initiation. Overexpression of HIC leads to a substantial increase in trichome density, while knockdown of HIC results in a marked decrease in density, confirming its role in trichome regulation. We identified a variant in the HIC promoter (-810 bp A to C) that increases transcription of HIC and trichome density in hirsute cotton compared with Gossypium hirsutum cultivars with fewer or no trichomes. Interestingly, although the -810 variant in the HIC promoter is the same in G. barbadense and hirsute cotton, the presence of a copia-like retrotransposon insertion in the coding region of HIC in G. barbadense causes premature transcription termination. Further analysis revealed that HIC positively regulates trichome density by directly targeting the EXPANSIN A2 gene, which is involved in cell wall development. Taken together, our results underscore the pivotal function of HIC as a primary regulator during the initial phases of trichome formation, and its prospective utility in enhancing aphid resistance in superior cotton cultivars via selective breeding.

Phloem sap from melon plants contains extracellular vesicles that carry active proteasomes which increase in response to aphid infestation.

The morphogenesis of higher plants requires communication among distant organs throughout vascular tissues (xylem and phloem). Numerous investigations have demonstrated that phloem also act as a distribution route for signalling molecules being observed that different macromolecules translocated by the sap, including nucleic acids and proteins, change under stress situations. The participation of extracellular vesicles (EVs) in this communication has been suggested, although little is known about their role. In fact, in the last decade, the presence of EVs in plants has originated a great controversy, where major concerns arose from their origin, isolation methods, and even the appropriate nomenclature for plant nanovesicles. Phloem sap exudates from melon plants, either aphid-free or infested with Aphis gossypii, were collected by stem incision. After sap concentration (Amicon), phloem EVs (PhlEVs) were isolated by size exclusion chromatography. PhlEVs were characterised using Nanoparticle Tracking Analysis, Transmission electron microscopy and proteomic analysis. Here we confirm the presence of EVs in phloem sap in vivo and the detection of changes in the particles/protein ratio and composition of PhlEVs in response to insect feeding, revealing the presence of typical defence proteins in their cargo as well as components of the proteasome complex. PhlEVs from infested plants showed lower particles/protein ratio and almost two times more proteolytic activity than PhlEVs from aphid-free plants. In both cases, such activity was inhibited in a dose-dependent manner by the proteasome inhibitor MG132. Our results suggest that plants may use this mechanism to prepare themselves to receive infectious agents and open up the possibility of an evolutionary conserved mechanism of defence against pathogens/stresses in eukaryotic organisms.

An effective dosage of neem (Azadirachta indica Juss) and aloe vera (Aloe barbadensis Miller) extracts against adult aphid (Myzus persicae Sulzer) and melon flies (Bactrocera cucurbitae Coquillet)

The objective of the study was to evaluate the efficaciousness dosage of aqueous extracts of neem (Azadirachta indica Juss) and aloe vera (Aloe barbadensis Miller) at different concentrations (40%, 60%, and 80%) against adult melon flies (Bactrocera cucurbitae Coquillet) and aphids (Myzus persicae Sulzer) in laboratory conditions. The experiments were designed and conducted from April to June 2023 at Sokoine University of Agriculture, Tanzania. The study found that as extract concentrations increased, there was a noticeable drop in insect survival. The dosage of 80% at 48 hours and 60% at 72 hours were observed to perform better as few were observed to survive. At the highest dosage of 80% and 60%, extracts from neem and aloe vera both resulted to 100% insect mortality. The results highlight the potential of aloe vera and neem extracts to have a positive effect on insect pest management rather than untreated crops.

Life table analysis and RNA-Seq reveal hormesis and transgenerational effects of deltamethrin on Aphis gossypii.

Deltamethrin, as a highly effective and broad-spectrum insecticide, has been widely used for agricultural pest control such as Aphis gossypii worldwide. Increasing evidence has shown that despite great economic benefits brought by it, deltamethrin has also non-negligible side effects. However, the potential risks and related molecular mechanisms remain largely unclear. Herein, the life table parameters and transcriptome sequencing analyses of the four successive aphid generations were performed to investigate the hormesis and transgenerational effects of deltamethrin on A. gossypii. The life table analysis showed that although the exposure of G0 aphid to 30% lethal concentration (LC30) deltamethrin significantly reduced the net reproduction rate (R0), intrinsic rate of increase (r), and fecundity of G0, but it significantly enhanced the R0 and fecundity of subsequent two generations (G1 and G2) of A. gossypii. Moreover, transcriptomic analyses showed that the signaling pathways related to posttranscriptional regulation (spliceosome), protein processing, longevity regulating, and cell proliferation (DNA replication, homologous recombination and non-homologous end-joining) were significantly up-regulated in G1 or G2 under LC30 deltamethrin treatment. Additionally, we also found that the deltamethrin-sulfoxaflor rotation of G0 and G1 still induced reproductive stimulation, but the reproductive stimulation induced by insecticides rotation treatment was significantly lower than that in the deltamethrin exposure alone. Our study demonstrates that sublethal concentrations of deltamethrin significantly enhanced the offspring fecundity of cotton aphid. In addition, our study also reveals the transcriptional response mechanism of hormesis-induced fecundity increase, providing valuable reference for optimizing the application of deltamethrin in integrated pest management. © 2024 Society of Chemical Industry.

Assessing the effects of imidacloprid exposure on the microbiota of Binodoxys communis (Hymenoptera: Braconidae) and gene expression

Imidacloprid is a potent neonicotinoid insecticide that exerts control over cotton aphids. Binodoxys communis is the predominant parasitic threat to cotton aphids, serving as a crucial biological means to control cotton aphids. Imidacloprid has been Sprayed to control cotton aphids, but it also causes toxic effects on the natural enemies of cotton aphids, such as parasitic wasps, Binodoxys communis. However, the sublethal impact of imidacloprid on parasitic antagonists has remained unclear. This study sought to investigate the sublethal effects of imidacloprid on B. communis at the biological phenotype and transcriptional level, as well as the impact of imidacloprid on the microbial composition in the B. communis. Our research indicated that the sublethal dosages of imidacloprid imparted significant biologic adverse impacts on B. communis, including extended larval and pupal stages, as well as reduced parasitism and emergence rates. Following treatment with imidacloprid, transcriptomic analysis identified 1263 significantly differentially expressed genes. These differentially expressed genes were predominantly annotated in metabolic routes, and the annotated genes mainly belong to the fatty acid metabolism pathway, the carbon metabolism pathway, and protein processing in the endoplasmic reticulum pathway. 16S rDNA sequencing results showed significant changes in the composition of the microbial community in B. communis after exposure to imidacloprid. A total of 14 bacteria exhibiting the highest abundance in parasitic wasps were found, and the microbiota abundance of Akkermansia, Bacteroides, Streptomyces, Helicobacter, and Prevotellaceae UCG_001 was noticeably reduced, while Lactobacillus, Escherichia Shigella, Ligilactobacillus, Lachnospiraceae, Rikenellaceae RC9_gut_group, Erysipelatoclostridium, Acinetobacter, Enterococcus, and Aquabacterium were significantly elevated. By evaluating the enrichment pathways of microbial functions, it was found that the microbial functions with significant changes in proportion were mainly annotated to the carbon, fatty acid, and amino acid (aa) metabolic pathways, which was consistent with the transcriptome sequencing results. This finding mirrored transcriptome analysis results. According to transcriptomics analysis and 16S rDNA sequencing data, imidacloprid limits changes in metabolic pathways of B. communis, including fatty acid metabolism, impacting the development and parasitic competence of B. communis. Accordingly, the gene expression linked to detoxification and the cytochrome P450 gene family was significantly elevated at 1 h and significantly declined after three days.

Efficacy of arginine kinase as a promising RNAi target in Aphis gossypii genome as revealed through aphid bioassay on field-grown transgenic cotton plants

The cotton aphid Aphis gossypii is a major agricultural pest of cotton that causes substantial damage to the crop not only by sucking sap but also through virus transmission. Globally adopted traditional and contemporary approaches to control aphid infestation have certain limitations and are hazardous to human health. RNA interference (RNAi) technology has unfolded its potential as an effective crop protection strategy against various pests. In this study, we adopted plant-mediated RNAi strategy to enhance aphid resistance in cotton by targeting arginine kinase (AK), which is a crucial enzyme responsible for energy homeostasis in insects. We selected a 312bp dsRNA fragment containing eight siRNAs and showing optimum GC content, Hb index, and stable secondary structure based on computational prediction studies. The binary construct expressing dsRNA was used to transform local cotton variety MNH886 and four transgenic lines were obtained in the T1 generation. Out of the four T1 transgenic cotton lines, dsA-7 exhibited the highest aphid mortality (73.3%), whereas, dsA-1, dsA-3 and dsA-6 revealed 60%, 61%, and 66.6% aphid mortality, respectively, in comparison to 13.3% mortality in the mock control cotton line. Moreover, significant knockdown in mRNA expression of AK was observed in aphids fed dsA-7 which was 79%. In comparison, 54%, 47%, and 45% downregulation was recorded in aphids which fed on dsA-6, dsA-3, and dsA-1 transgenic cotton lines, respectively. These results revealed that plant-mediated downregulation of aphid RNA induced significant RNA interference in A. gossypii which resulted in considerable aphid mortality and led to plant protection against aphids.

Compatibility and Toxicity of Lecanicillium lecanii with Insecticides against Cotton Aphids In vitro

Background: Lecanicillium lecanii is the most effective entomopathogenic fungus against all stages of sucking pests like aphids, whiteflies, scale insects, thrips and mealybugs. The compatibility of fungi with commonly used insecticides was investigated in this study. Aim: To study the In vitro compatibility and toxicity of Lecanicillium lecanii with insecticides against cotton aphids. Study Design: Completely Randomized Design. Methodology: Six different insecticides were evaluated under in vitro conditions against L. lecanii by the poison food technique. The results showed that insecticides, viz., Dinotefuran 20 SG (0.006%), Afidopyropen 50 g/L DC (0.1%), Diafenthiuron 50 WP (0.06%) and Buprofezin 25 SC (0.05%), were rated as harmless and proved compatible with L. lecanii. Pyriproxyfen 10 EC (0.016%) and Tolfenpyrad 15 EC (0.03%) were moderately harmful to L. lecanii. Furthermore, the toxicity of insecticides alone and in combination with the entomopathogenic fungus L. lecanii against the cotton aphid, Aphis gossypii, was assessed by topical application bioassay under laboratory conditions. Results: Cent percent mortality of A. gossypii was recorded with Diafenthiuron 50 WP (0.06%), Dinotefuran 20 SG (0.006%) and Afidopyropen 50 g/L DC (0.1%) at the recommended dose and their combination at half of the recommended dose with L. lecanii (1×107 conidia/ml) at 72 h after treatment. While minimum mortality was observed with the individual treatment of L. lecanii (1×107 conidia/ml). Conclusion: This study suggests that the most suitable insecticides at half of the recommended dose, when combined with L. lecanii, can be effectively integrated into pest management programs.

Abundance and diversity of cotton insect pests under repeatedly cultivated cotton fields of Tanzania.

Cotton production in Tanzania is facing significant challenges due to insect pests that cause extensive damages to the crop. The most notable pests include the African bollworm (Heliothis armigera Hubner), Spiny bollworm (Earias biplaga Walker), Cotton stainers (Dysdercus sidae (Herrich-Schaeffer), Cotton Aphids (Aphis gossypii Glover), Thrips (Thrips tabaci Lindeman), Jassids (Amrasca biguttula, Bigutula), Leafhoppers (Cicadellidae jassidae), and Whiteflies (Bemisia tabaci Genn). If left uncontrolled, these pests can cause up to 60% damage to the crop. Despite the importance of cotton and the fact that most of these pests are endemic, there are scanty knowledge on the dynamics and distribution of cotton pests across the seasons of the year and crop's phenological growth stages (germination, vegetative growth, flowering and boll formation) in areas under repeated cultivation of the crop in Tanzania. Here we report on the influence of seasons and cotton's phenological stages on the abundance, diversity, distribution and richness of cotton insect pests. The study was conducted in the Misungwi district for two cotton-growing seasons, using the UKM08 cotton variety. Stick traps and handpicking methods were deployed in catching the cotton insect pests. On average, a total of 8,500 insect specimen of diverse families and species were collected every season. The four dominant species among the collected were Aphis gossypii (17.37%), Amrasca biguttula (11.42%), Nezara viridura (10.7%), and Bemisia tabacci (10.68%). Both cotton phenological growth stages and seasons significantly (p<0.05) influenced the abundance, diversity, distribution and richness of cotton insect pests. In particular, the phenological growth stage 3 exhibited greater diversity of insect pests. The pests' distribution patterns remained relatively uniform across the crop growth stages. Findings from the present study could contribute to developing sustainable pest management strategies in areas under repeated cotton production in Tanzania and elsewhere.

Influences of Salt Stress on Cotton Metabolism and Its Consequential Effects on the Development and Fecundity of Aphis gossypii Glover.

The degree of global soil salinization is gradually deepening, which will inevitably affect agricultural ecology. It has been found that salt stress induces the resistance of host plants to phytophagous pests. However, little is known about the effects of salt-stressed cotton plants on the fitness of cotton aphids (Aphis gossypii Glover). In this study, we investigated the differences between cotton metabolomes under mild (75 mM NaCl) and moderate (150 mM NaCl) salinity conditions and their effects on the fitness of cotton aphids. The results showed that 49 metabolites exhibited significant upregulation, while 86 metabolites were downregulated, with the increasing NaCl concentration. The duration of nymphal aphids under 150 mM NaCl significantly extended to 6.31 days when compared with the control (0 mM NaCl, 4.10 days). Meanwhile, the longevity of adult aphids decreased significantly under 75 and 150 mM NaCl, with an average of 10.38 days (0 mM NaCl) reduced to 8.55 and 4.89 days, respectively. Additionally, the total reproduction number of single females decreased from 31.31 (0 mM NaCl) to 21.13 (75 mM NaCl) and 10.75 (150 mM NaCl), whereas the survival rate of aphids decreased from 81.25% (0 mM NaCl) to 56.25% (75 mM NaCl) and 34.38% (150 mM NaCl) on the 12th day. These results support the hypothesis that plants growing under salt stress are better defended against herbivores. Furthermore, 49 differential metabolites were found to be negatively correlated with the longevity and fecundity of adult aphids, while 86 different metabolites showed the opposite trend. These results provide insights into the occurrence and control of cotton aphids amidst the escalating issue of secondary salinization.

Pyridine Derivatives as Insecticides: Part 6. Design, Synthesis, Molecular Docking, and Insecticidal Activity of 3-(Substituted)methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles Toward Aphis gossypii (Glover, 1887).

Three new series of 3-(substituted)methylthio-4-cyano-5,6,7,8-tetrahydroisoquinolines were designed and synthesized starting from readily available materials, 7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(4-pyridyl, 3-pyridyl, phenyl, 4-methoxyphenyl, or 4-chlorophenyl)-5,6,7,8-tetrahydrosoquinoline-3(2H)-thiones 2a-e in high yields and very pure states. Thus, compounds 2a-e were reacted with some chloro reagents, namely, N-aryl-2-chloroacetamides 3a-f and N-(naphthalen-2-yl)-2-chloroacetamide (3g) under mild basic conditions to give the first two series of the target compounds, 3-(N-aryl)carbamoylmethylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 4a-l and 5a-e, respectively. Reaction of compounds 2d,e with ethyl chloroacetate under the same conditions gave the other series, 3-ethoxycarbonyl-methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 6d,e. Structural formulas of all of the new compounds were elucidated and confirmed by elemental and spectral analyses. The insecticidal activity of all synthesized 5,6,7,8-tetrahydrosoquinolines toward the nymphs and adults of Aphis gossypii were screened. The results revealed the promising insecticidal activity of some tested compounds. Moreover, the structure-activity relationships as well as molecular docking of some representative compounds were evaluated.

Impact of leaf trichomes and stomatal density on the response of three soybean varieties to sucking pest infestation

Chemical pesticides disrupt local ecosystems, reduce populations of natural predators, and contribute to the evolution of pest resistance. Therefore, developing pest-resistant crop varieties is one of the most promising and environmentally friendly alternatives for pest control today. In the present study field experiments were conducted over two consecutive growing seasons in 2022 and 2023 to explore pest resistance among three soybean varieties viz. Crawford, Giza 111, and Giza 22. The research aimed to assess pest infestation resistance among these varieties, considering various leaf morphological factors. Four key pests were evaluated in the study viz. whiteflies (Bemisia tabaci Genn), spider mites (Tetranychus urticae Koc), aphids (Aphis gossypii Glover), and thrips (Thrips tabaci Lind)). The soybean varieties exhibited differences in susceptibility, and pest density varied across the two growing seasons. Crawford and Giza 111 demonstrated lower resistance, characterized by reduced leaf hair density and an increased number of stomata per leaflet. In contrast, Giza 22 was the most susceptible, featuring a higher density of trichomes and lower stomata density. In terms of field yield, Crawford produced the highest yield, followed by Giza 111, while Giza 22 yielded the least. The results of this study underscore the importance of selecting resistant plant varieties in future pest resistance improvement programs.

Disrupted oxylipin biosynthesis mitigates pathogen infections and pest infestations in cotton (Gossypium hirsutum).

Cotton (Gossypium hirsutum) is the world's most important fiber crop, critical to global textile industries and agricultural economies. However, cotton yield and harvest quality are undermined by the challenges introduced from invading pathogens and pests. Plant-synthesized oxylipins, specifically 9-hydroxy fatty acids resulting from 9-lipoxygenase activity (9-LOX), enhance the growth and development of many microbes and pests. We hypothesized that targeted disruption of 9-LOX-encoding genes in cotton could bolster crop resilience against prominent agronomic threats. Fusarium oxysporum f. sp. vasinfectum (FOV), Aphis gossypii (cotton aphid), and Tobacco rattle virus induced the expression of 9-oxylipin biosynthesis genes, suggesting that the 9-LOX gene products were susceptibility factors to these stressors. Transiently disrupting the expression of the 9-LOX-encoding genes by virus-induced gene silencing significantly reduced target transcript accumulation, and this correlated with impaired progression of FOV infections and a significant decrease in the fecundity of cotton aphids. These findings emphasize that the cotton 9-LOX-derived oxylipins are leveraged by multiple pathogens and pests to enhance their virulence in cotton, and reducing the expression of 9-LOX-encoding genes can benefit cotton crop vitality.

The Belowground-Aboveground Interactions of Zucchini: The Effects of Trichoderma afroharzianum Strain T22 on the Population and Behavior of the Aphid Aphis gossypii Glover and Its Endoparasitoid Aphidius colemani Viereck.

Fungi belonging to the genus Trichoderma have received high consideration in agriculture due to their beneficial effects on crops from their plant promotion effects and protection from disease. A role of Trichoderma fungi in triggering plant defense mechanisms against insect pests, either directly or by natural enemy attraction, has been proposed, even if the results in different studies are controversial. In this present study, using zucchini plants as a model species, we investigated the effects of Trichoderma afroharzianum strain T22 plant inoculation on the cotton aphid Aphis gossypii and its endoparasitoid Aphidius colemani. Our results showed that the inoculation with T. afroharzianum T22 promotes A. gossypii population growth and makes zucchini more attractive to the aphid. The higher abundance of aphids on Trichoderma-inoculated zucchini was compensated for by a higher presence of the mummies of Aphidius colemani. In this present study, we recorded a higher zucchini biomass, thereby confirming that Trichoderma can act as a plant growth inducer.