Characterizing biological parameters of Myzus persicae biotypes and diagnosing R81T linked neonicotinoids resistance.

We conducted field surveys and experiments to evaluate the hypothesis that predation is an important driving factor determining the degree of coexistence between red and green morphs of the pea aphid Acyrthosiphon pisum. Theory suggests that the different colour morphs are differentially susceptible to natural enemies and selection by predation which in turn leads to variable relative abundances of red and green morphs among host plants across landscapes. Our field surveys on pea and alfalfa revealed, however, that the colour morphs tended to coexist closely in a ratio of one red to three green aphids across fields with different host plant monocultures. Experimentation involving manipulation of the relative abundances of the two colour morphs on host plants pea and alfalfa with and without predator presence revealed that red morphs had higher or same fitness (per capita reproduction) than green morphs on both pea and alfalfa only when in the proportion of one red/three green proportion. Moreover, experimentation evaluating predator efficiency revealed that red morphs are safest from predation when in a 1 : 3 ratio with green morphs. These results suggest that in addition to predation selection effects, red morphs may behaviourally choose to associate with green morphs in a narrow 1 : 3 ratio to maximize their fitness. This evidence, along with existing published data on red and green morph anti-predator behaviour indicates that a 1 : 3 red and green morph coexistence ratio is driven by a balance between predation pressure and behavioural assorting by red morphs across landscapes. In this way predators may have ecological-evolutionary consequences for traits that affect the colour morphs' proportion and tolerances to selective pressure.

The tobacco aphid, Myzus persicae nicotianae is an economically important pest of tobacco. Damage is through direct injury by sucking sap of infested plants as well as reduction of the quality of the leaf by leaving honey-dew which encourages the subsequent growth of sooty-mould. In addition to this, aphids also transmit economically important virus diseases such as the bushy-top virus, the alfalfa mosaic virus and the potato virus-Y. Before 2002, the main colour form of the tobacco aphid in Zimbabwe was green. However, during the 2003/2004 tobacco season, concerns were raised where red forms of the tobacco aphid were observed to be more prevalent than the green form. During the 2004/2005 tobacco season, green forms of the tobacco aphid could only be found with difficulty. In intensive research spanning three years, the days to adulthood, days to 1st nymph, nymphs/day, longevity, fecundity and survival of the red morph were compared to that of the green aphid. Across all years, days to adulthood were the same for the two forms. The red morph produced more nymphs/day than the green morph. Longevity was similar but fecundity was 1½ to 2 times higher for the red morph than the green aphid. The red morph survived longer than the green aphid. These parameters combined to give the red morph of the tobacco aphid a greater reproductive potential and rate of population increase over the green morph thereby partly explaining the sudden increase in this pest in the recent past.

Currently, pesticide production and use are on the rise globally. This trend is certain to continue in the coming decades with residues posing risks to the environment and human health even at low levels. Although various aspects of pesticides and their possible implications have widely been studied, such studies have mostly been carried out in developed countries leaving the rest of the world with little scientific information. We present here the results of a study on the occurrences, concentrations, and ecological risks of 30 pesticide residues (PRs) in water and sediment samples from a tropical freshwater Lake Hawassa in the Ethiopian Rift Valley. A total of 54 composite samples of water and sediment were collected from three sampling sites on three occasions. The samples were prepared by quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique, and analyzed using GC-MS at Bless Agri Food Laboratory Service located in Addis Ababa, Ethiopia. The study applied the risk quotient (RQ) method to scrutinize the risks posed to aquatic biota by the detected PRs. The results showed occurrences of 18 and 20 PRs in the water and sediment samples, respectively. The majority, 78 and 75% of the detected PRs in water and sediment samples, respectively represent the organochlorine chemical class. Concentrations of heptachlor epoxide were significantly (p ≤ 0.001) higher than those of the remaining pesticides in both matrices. Of the pesticides detected, 77% were present in water and 83% in sediment samples and pose a serious risk (RQ ≥ 1) to the Lake Hawassa biota. This calls for further research to investigate the risks to human health posed by the PRs. The findings of this study can contribute to the development of global protocols, as they support the concerns raised about the ecological and public health impacts of PRs on a global level.

Use of pesticide has become part of modern day agricultural practice. Some pesticides can remain in the environment for decades and contaminate surface water that is used for irrigation of produce. Two studies were conducted- first to examine possible pesticide residue in surface water and some fruits, vegetables and cereals in Louisiana; and second was to alleviate possible pesticide residues in the water using zeolite filtration. Samples of 8 foods (tomato, corn, rice, blueberry, cucumber, cabbage, wheat and melon) and 35 surface waters were studied using a QuEChERS extraction method for food samples and an EPA method for the water samples. Gas chromatography-mass spectrometry was used to analyze water and food samples. Alleviation of pesticide residues was attempted for 10 water samples using a natural zeolite filtration. One water sample was filtered through a surfactant (HDTMA-Cl)-modified-zeolite. Eighteen pesticides were detected in the surface water samples and 5 in the food samples. Pesticides detected were below FDA limit but 0.18 ppm cypermethrin found in tomato was 90 % close to the FDA limit (0.2 ppm). Alleviation was achieved in 9 water samples out of 10 samples that were filtered through zeolite. The highest removal of pesticides from water with zeolite was 100 % in bifenthrin in CLC sample, followed by 99.1 % in atrazine in the same sample. Minimum reduction of 10.9 % was in metolachlor in sample BRH. Further reduction of pesticide residues up to 50 % was recorded in the SMZ treatment as the concentrations of 4 out of 8 pesticide residues were reduced. This study suggests the need to intermittently monitor pesticide contamination in our food and water.

Levels of organochlorine (OC) and organophosphorus (OP) pesticide residues in fish, sediments and water and their health risk associated with the consumption of the fish from the Tono Reservoir, Ghana were evaluated. The analytical methods included solvent extraction of the pesticide residues using ultrasound sonication and soxhlet extraction and their subsequent quantification using GC equipped with electron capture detector and pulse flame photometric detector after clean-up on activated silica gel/anhydrous sodium sulphate. A total of 29 pesticides comprising 16 OCs and 13 OPs were analyzed, out of which aldrin, p,p′-DDE and p,p′-DDD were detected in fish and sediment samples. The results showed that all the residues in water had their concentrations below the detection limit. Mean concentrations of organochlorine pesticide (OCP) residues in fish ranged from 0.017 to 0.17, 0.043 to 0.30, 0.027 to 0.243 and 0.097 to 0.263 µg/g in Sarotherodon galilaeus, Clarias anguillaris, Schilbe intermedius and Marcusenius senegalensis respectively. Mean concentrations of organophosphates pesticides ranged from 0.080 to 0.090, 0.080 to 0.087 and 0.050 to 0.063 µg/g in C. anguillaris, S. intermedius and M. senegalensis respectively. The level of chlorpyrifos in S. galilaeus was 0.160 µg/g. Mean concentrations of OCP residue in sediments ranged from 0.047 to 0.090 µg/g. Aldrin recorded the highest level while p,p′-DDD recorded the lowest level. The mean concentrations for all the detected residues were below the WHO/FAO maximum residue limits. Health risk estimation revealed that aldrin in M. senegalensis had great potential for systemic toxicity to consumers.

Simple SummaryThe green peach aphid (Myzus persicae) is one of the most damaging insect pests affecting vegetable and ornamental crops worldwide, due to its feeding activity and ability to transmit plant viruses. Although synthetic chemical pesticides are commonly used to manage M. persicae, their widespread use raises concerns about human health, environmental contamination, pesticide residues in food, harm to beneficial insects, and the development of resistance. As a result, there is growing interest in safer, eco-friendly alternatives. In this study, we used sucrose-based artificial diet assays supplemented with double-stranded RNA (dsRNA) to identify RNA interference (RNAi) effectors capable of inducing gene silencing and mortality in M. persicae through ingestion. Defining effective gene targets is a critical first step toward developing a non-toxic, environmentally sustainable RNAi-based technology for controlling M. persicae and the viruses it spreads.Aphids are sap-sucking pests that cause substantial damage to fruit and fibre crops through direct feeding and transmission of plant viruses. While chemical pesticides remain the primary method of control, their use raises concerns related to human health, environmental contamination, pesticide resistance, and impacts on beneficial insects. As a sustainable alternative, spray-on double-stranded RNA (dsRNA) technology offers a promising approach to induce RNA interference (RNAi) in target pests. For RNAi to be effective against sap-sucking insects like the green peach aphid (Myzus persicae), it is essential to identify genes whose silencing disrupts vital physiological functions. In this study, artificial diet (AD)-based feeding assays were used to evaluate dsRNAs targeting eight genes involved in neural function, osmoregulation, feeding behaviour, and nucleic acid/protein metabolism. dsRNAs were administered individually, in combinations, or as a multi-target stacked construct. After 98 h of feeding, aphid mortality ranged from 14 to 72% (individual targets), 78–85% (combinations), and 54% (stacked construct). Transcript knockdown varied from 6.3% to ~54%, though a consistent correlation with mortality was not always observed. The gene targets and combinatorial dsRNA strategies identified in this study provide a foundation for developing RNAi-based crop protection technologies against M. persicae infestation.

We are working on the development of a real-time electrochemical sensor based on an immunoassay detection system to detect and quantify the presence of pesticide residues in ground water. Highly selective and sensitive immuno-reactions are being investigated to be optimized in order to bring them into the level of real-time in-line sensors. In this project a competitive immunoassay between surface immobilized 2,6-dichlorobenzamide (BAM) haptens and BAM present in the water sample using an anti-BAM monoclonal antibody is being described. 2,6-Dichlorobenzamide (BAM) is a degradation product of the herbicide, dichlobenil which has been used extensively in the past and it is among the most frequently found pesticide residues in European ground water. BAM is highly resistant to further degradation and is fairly soluble in water. We have synthesized and immobilized a small library of BAM haptens and compared the affinity constants of the antibody towards this library. Furthermore, since regeneration of the BAM-hapten surface is a prerequisite for the development of a real-time electrochemical sensor with immunoassay-based detection, studies on regeneration of surfaces, modified with the newly synthesized BAM-haptens has been preformed and compared and correlated to the measured affinity constants. By using conventional ELISA we were able to indicate that one of the immobilized BAM haptens with an intermediate affinity towards the anti-BAM antibody was better in terms of regeneration. Design and fabrication of a fully automated microfluidic based on this immunoassay and electrochemical detection are in progress.

Reduction of environmental pollution incurred from pesticide use is very important. Zeolite is a natural mineral capable of removing certain chemical contaminants from water. This study was carried out to test the effect of zeolite treatment on pesticide residue alleviation in surface water. Ten surface water samples were treated with natural zeolite by filtering through. An EPA method was used to extract pesticide residue from the water samples and the surfactant used to modify the net charge on the zeolite was hexadecyltrimethylammonium chloride (HDTMA-Cl). Gas chromatography-mass spectrometry was used to analyze water samples. Alleviation was achieved in all the 10 water samples that were filtered through zeolite. The highest removal of pesticides from water with zeolite included 100% of bifenthrin in sample CLC, atrazine in BPH, CDG and LBT; metolachlor in CLC, LBT, BCH, TRH2 and BPI; acetolachlor in BBH and BCH; azoxystrobin in BBH; desethylatrazine in BCH and BPI; metribuzin in BCH, TRH2 and BPI; and both clomazone and bromacil in sample BDC. A minimum reduction of 10.9% was found for metolachlor in sample BRH. Further reduction of pesticide residues up to 50% was recorded in the SMZ treatment as the concentrations of 4 out of 8 pesticide residues were reduced. This study confirms the potential of both the natural zeolite-Clinoptilolite, and SMZ of alleviating pesticide residues in water.

Carotenoids play many crucial roles in organisms. Recently, the de novo synthesis of carotenoids has been reported in pea aphid (Acyrthosiphon pisum) through horizontally transferred genes. However, their upstream pathway in the pea aphid is poorly understood. Geranylgeranyl diphosphate synthase (GGPPS) is the functional enzyme in the synthesis of geranylgeranyl diphosphate (GGPP) which is a precursor for the biosynthesis of many biological metabolites, including carotenoid synthesis. In this study, we performed a series of experiments to characterize GGPPS gene and its association with carotenoid biosynthesis. (1) determining the transcript abundance and carotenoid content in two geographical strain with red and green morphs, and (2) examining the abundance of carotenoid related genes and carotenoid levels after silencing of GGPPS in both red and green morphs. We observed that GGPPS was more highly expressed in the green morph than in the red morph of two strains of the pea aphid. The total level of carotenoids was also higher in green morphs than in red morphs in both strains. In addition to the total carotenoid difference, the carotenoids found in the two morphs also differed. There were α-carotene, β-carotene, and γ-carotene in the green morphs, but three additional carotenoids, including cis-torulene∗, trans-torulene∗, and 3,4-didehydrolycopene∗, were present in the red morphs. Silencing the GGPPS by RNAi in both the red and green morphs decreased the expression of some carotenoid biosynthesis-related genes, including carotenoid synthase/cyclase genes and carotenoid desaturase genes in green morphs. Carotenoid levels were decreased in both green and red morphs. However, the specific carotenoids present were not changed after silencing GGPPS. These results demonstrated that GGPPS may act as the upstream enzyme to influence the synthesis of the total amount of carotenoids. The present study provided important molecular evidence for the conserved roles of GGPPS associated with carotenoids biosynthesis and will enhance further investigation on the mechanisms of carotenoid biosynthesis in pea aphid.

The study was aimed at determining the levels of organochlorine pesticides residues in water, sediment and fish species at River Tella to find out the extent of pesticide contamination and accumulation in the river. Total of fourteen (14) organochlorine pesticide residues were analyzed which include Delta lindane, Alpha Lindane, Beta Lindane, Gamma Lindane, Heptachlor, Aldrin, Heptachlor Epoxide, Endosulfan I, Endosulfan II, P’P-DDE, P’P-DDD, P’P-DDT and Methoxychlor. The water sample was subjected to liquid-liquid extraction method while the fish and the sediment samples were subjected to soxhlet extraction. The extracts were later analyzed for organochlorine pesticide residues using Gas-Chromatography coupled with mass spectrometer (GC-MS). The study has revealed that the level of pesticides residues in water was less than that of fish and sediment which was also below the WHO/FAO values. It was also observed that high concentrations recorded were recorded in high in Gamma Lindane (24.71), follow by Alpha Lindane (23.70) and Beta Lindane (4.50). Mormyrus rume follow by Claria gariepinus while the Tilapia zilli recorded low concentration of the pesticide residues. The Aldrin recorded high concentration of 5.11 ppm in Mormyrus rume follow by Endosulfon II which recorded the concentration of 25.03 ppm also in Mormyrus rume. Endrin also recorded the concentration of 4.88 ppm in Clarias. gariepinus. The lowest pesticide residues was recorded in p,p'-DDD (0.01 ppm), p,p'-DDT (0.03 ppm), Methoxychlor (0.01 ppm). The Heptachlor epoxide and P’P-DDE were not detected in water sample. The presence of high concentration in fish may pose a great danger when these fish are being consumed over time. Regular monitoring is therefore required to control the levels of pesticide residues in the water bodies. The measurement of the fish showed that Clarias gariepinus had the average length of 15.89 cm, and average weight of 179.87 g. Mormyrus rume had the average length of 15. 18 cm, and average weight of 210. 54g. Tilapia zilli was the least species of fish sample with a length of 12.96 cm and average weight of 96.88 g. The water quality parameters of the river were also studied, which recorded the temperature of 28.89 oC was recorded, pH value of 9.01, Conductivity value of 40.11, DO value of 6.14 and TDS of 2.35.

The interplay between the host plant of an insect herbivore and an insect predator (here two-spot ladybird beetles; Adalia bipunctata (L).; Coleoptera: Coccinellidae), feeding upon such a herbivore was examined in the laboratory as factors possibly determining the differential abundance and success of green and red host races of pea aphid, Acyrthosiphon pisum Harris. The experiment comprised three treatments: two host plants (bean and clover), two treatment levels (control and predation) and three colour morph levels (green alone, red alone and green and red in mixture). Green morphs had higher fitness on the general host plant, bean Vicia faba, than on the derived host, clover (Trifolium pratense), in the absence of predation. Although green morph fitness was reduced by predation when infesting bean together with reds, there was no observable net fitness loss due to predation on clover in mixed colonies with red morphs. Red morphs exhibited fitness loss alone on both bean and clover, while clover plants seemingly prevented fitness loss in the presence of predation when red morphs were mixed with green ones. According to this scenario, when colour morphs existed as a mixed colony, the net fitness of either pea aphid morph was not influenced by predation on clover. Predators had significant effects only on red morphs on broad bean either when alone or were mixed together with green morphs. Thus, only red morphs experienced the benefits of switching from the general to the derived host red clover in the presence of predation. For green morphs, there was no apparent cost of switching host plants when they faced predation. Hence, the co-existence of green-red colour polymorphism of pea aphids on single host plants appears to be maintained by the morph gaining fitness on the derived host due to a host plant– and predation–reduction effect. These findings have important implications for understanding the ecology and evolution of host switching by different colour-plant host adapted races of pea aphids

Simple analytical methodology based on solid phase extraction for monitoring pesticide residues in natural waters

Body-color polymorphisms in insects are often explained by environmental selective advantages. Differential fitness related to body coloration has been demonstrated in Myzus persicae (Sulzer): performance of the red morph is in general better than that of the green morph on tobacco plants. However, the molecular mechanism involved is largely unclear. Here we showed that the red morph of M. persicae had higher expression of a carotenoid desaturase CarD763 in the whole body, salivary gland and saliva relative to the green morph. Also, 18% individuals displayed faded red body color 5 days post dsCarD763 treatment. Furthermore, knockdown of CarD763 in the red morph significantly prolonged the time needed to locate phloem and shortened the duration of phloem feeding. Honeydew production and survival rate decreased as well. In contrast, overexpression of CarD763 in tobacco leaves facilitated aphid feeding, enhanced honeydew production and improved the survival rate of aphids. Compared with those fed by dsGFP aphids, plants infested by dsCarD763-treated aphids had higher ROS accumulation, lower lycopene content and photosynthetic rate, and maximum photon quantum yield. The reverse was true when plants overexpressed CarD763. These findings demonstrated that CarD763, a red morph-specific salivary protein, could enhance aphid feeding and early colonization by promoting plant photosynthesis. © 2024 Society of Chemical Industry.

Control of red and green morphs of the tobacco aphid, Myzus nicotianae Blackman, was investigated in field and laboratory tests on flue-cured tobacco in Georgia during 1987–1989. Acephate provided good control of both morphs at 0.75 and 0.5 lbs. AI/acre, and fair to poor control of both morphs at 0.25 and 0.125 lbs. AI/acre. Methomyl, endosulfan, and Endocide Plus (endosulfan plus parathion) also provided effective control of both morphs. Malathion, oxamyl, and tralomethrin provided significantly better control of the green morph than the red morph. Microencapsulated methyl parathion was totally ineffective in controlling either green or red color forms. In laboratory tests, the residual activity of acephate provided high mortality and a reduction in live nymphs produced for up to 14 days after application for both morphs, although these effects were more pronounced with green aphids. The residual activity of methomyl had no adverse effects on either morph 3 days after treatment.

Organochloride pesticides remain widely used in Africa, despite their potential public health issues. This study assessed the organochloride pesticides (OCPs) residues in water and silver catfish from Ajiwa Reservoir. The concentrations of OCPs in water and fish samples were determined using GC analysis, while One-way analysis of variance (ANOVA) was used to compare the means for each parameter among the selected stations (Kadaji, Gamji and Kundu waje). Significantly higher concentrations of Aldrin (2.66±0.44ngL-1), Diedrin (1.71±0.38ngL-1), Endrin aldehyde (2.31±0.22ngL-1), Endrin ketone (2.56±0.22ngL-1), beta-BHC (1.70±0.66ngL-1), gamma- BHC (0.85±0.30ngL-1) and delta- BHC (1.19±0.47ngL-1) were found in the gills of fish from Kadaji. Also, significantly higher Endosulfan (2.24±0.70 gL-1), Methoxychlor (2.63±0.95gL-1) and p,p'-DDE (1.77±0.34ngL-1) were found in the muscles of fish from Gamji. In contrast, Diedrin (2.111±0.59ngL-1) and Endrin aldehyde (3.84±0.86ngL-1) were significantly higher in the fish muscles from Kadaji. The OCPs in the water were not significantly different among the stations except Alpha-BHC (1.50±0.63 ngL-1). The study revealed the presence of various organochlorine pesticides in the fish tissues and the water, indicating a possible bioaccumulation in the fish. Although all the organochlorines were not above the safety level, however, it is not impossible that this might lead to possible health issues in the future