Aphid Development Research Articles

Effects of Several Botanical Insecticides Applied in Different Periods to Control Aphids (Macrosiphoniella sanborni Gillete) on Chrysanthemum

Pest management in the agricultural process has faced worldwide economic and ecological issues related to chemicals usage. Botanical insecticides have long been considered promising alternatives to control pests because botanicals reputedly pose a minor threat to the environment and human health. Some studies have evaluated several botanical insecticides to control aphids in chrysanthemum. The research was conducted under plastic house conditions at the Indonesian Ornamental Crops Research Institute from January to December 2018. Leaf extract of T. sinensis, T. diversifolia and A. indica at the concentration of 3 and 3.5 g/l, processed oil of C. nardus at the concentration of 2.5 and 5 g/l and synthetic insecticide Imidacloprid 1 g/l were sprayed in the morning or late afternoon. The results showed that aphid attacks severity and percentage of attacked plants were lower when the insecticides were applied in the late afternoon. Slightly softer than synthetic chemicals, the leaf extract of T. sinensis at 3 g/l suppressed the aphid development more effective for about 55.93% than other botanicals treatments. On reproductive properties, the leaf extract of T. sinensis at 3 and 3 g/l and T. diversifolia at 3 g/l induced a higher percentage of open flower for more than 65% than synthetic insecticides, Imidacloprid.

Effects of Constant versus Fluctuating Temperatures on Fitness Indicators of the Aphid Dysaphis plantaginea and the Parasitoid Aphidius matricariae.

Simple SummaryLike all organisms, insects encounter temperatures that fluctuate on different time scales: within a day, between days, or throughout the seasons. However, most studies on the impact of temperature on insect physiology, behavior, morphology, or ecology have focused on constant temperatures tested in the laboratory. In our study, we wanted to know if fluctuating temperatures during the day (7–17 °C, average 12 °C) can affect insects differently compared to a constant temperature of 12 °C. We used, as a model, the apple aphid Dysaphis plantaginea, a major threat to apple orchards worldwide, and its parasitoid Aphidius matricariae, which is used in biological control. We found that many traits—but not all—were affected. In particular, the fluctuating thermal regime reduced the development time of aphids and parasitoids, improved the rate of parasitism, and tended (albeit slightly) to increase the longevity of both species. In contrast, we did not find strong effects on morphological traits. Our results can be used to better predict how these agronomically important insects behave in orchards, how ecologically-relevant fluctuating temperatures affect host–parasitoid relationships, and ultimately what the implications are in the context of climate change and biological control.Testing fluctuating rather than constant temperatures is likely to produce more realistic datasets, as they are ecologically more similar to what arthropods experience in nature. In this study, we evaluated the impact of three constant thermal regimes (7, 12, and 17 °C) and one fluctuating thermal regime (7–17 °C with a mean of 12 °C) on fitness indicators in the rosy apple aphid Dysaphis plantaginea, a major pest of apple orchards, and the parasitoid Aphidius matricariae, one of its natural enemies used in mass release biological control strategies. For some—but not all—traits, the fluctuating 7–17 °C regime was beneficial to insects compared to the constant 12 °C regime. Both aphid and parasitoid development times were shortened under the fluctuating regime, and there was a clear trend towards an increased longevity under the fluctuating regime. The fecundity, mass, and size were affected by the mean temperature, but only the mass of aphids was higher at 7–17 °C than at a constant 12 °C. Parasitism rates, but not emergence rates, were higher under the fluctuating regime than under the constant 12 °C regime. Results are discussed within the framework of insect thermal ecology and Jensen’s inequality. We conclude that incorporating thermal fluctuations in ecological studies could allow for the more accurate consideration of how temperature affects host–parasitoid interactions and insect responses to temperature change over time.

Controlling insecticide resistant clones of the aphid, Myzus persicae, using the entomopathogenic fungus Akanthomyces muscarius: fitness cost of resistance under pathogen challenge.

Biological control is a cornerstone of integrated pest management and could also play a key role in managing the evolution of insecticide resistance. Ecological theory predicts that the fitness cost of insecticide resistance can be increased under exposure to invertebrate natural enemies or pathogens, and can therefore increase the value of integrating biological control into pest management. In this study of the peach potato aphid, Myzus persicae, we aimed to identify whether insecticide resistance affected fitness and vulnerability of different aphid clones to the entomopathogenic fungus Akanthomyces muscarius. Insecticide resistant clones were found to be slightly less susceptible to the pathogen than susceptible clones. However, this pattern could also be explained by the influence of length of laboratory culture, which was longer in susceptible clones and was positively correlated with susceptibility to fungi. Furthermore, resistance status did not affect aphid development time or intrinsic rate of increase of aphids. Finally, in a cage trial the application of fungus did not increase the competitive fitness of insecticide resistant clone 'O'. We found no fitness cost in reproductive rate or pathogen susceptibility associated with chemical resistance in M. persicae. In contrast, some susceptible clones, particularly those subject to decades of laboratory rearing, showed enhanced susceptibility to a fungal pathogen, but not reduced reproductive fitness, an observation consistent with down-regulation of costly immune functions in culture. Overall, fungal pathogen control is compatible with insecticides and should not increase the selection pressure for resistance of M. persicae to chemical insecticides.

Changes in Antioxidative, Oxidoreductive and Detoxification Enzymes during Development of Aphids and Temperature Increase.

Temperature, being the main factor that has an influence on insects, causes changes in their development, reproduction, winter survival, life cycles, migration timing, and population dynamics. The effects of stress caused by a temperature increase on insects may depend on many factors, such as the frequency, amplitude, duration of the stress, sex, or the developmental stage of the insect. The aim of the study was to determine the differences in the enzymatic activity of nymphs and adult aphids Aphis pomi, Macrosiphum rosae and Cinara cupressi, and changes in their response to a temperature increase from 20 to 28 °C. The activity of enzymatic markers (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), β-glucosidase, polyphenol oxidase (PPO) and peroxidase (POD)) in aphid tissues was analysed for three constant temperatures. The results of our research showed that the enzymatic activity of aphids (measured as the activity of antioxidant, detoxifying and oxidoreductive enzymes) was mainly determined by the type of morph. We observed a strong positive correlation between the activity of the detoxifying and oxidoreductive enzymes and aphids’ development, and a negative correlation between the activity of the antioxidant enzymes and aphids’ development. Moreover, the study showed that an increase in temperature caused changes in enzyme activity (especially SOD, CAT and β-glucosidase), which was highest at 28 °C, in both nymphs and adults. Additionally, a strong positive correlation between metabolic activity (heat flow measured by microcalorimeter) and longevity was observed, which confirmed the relationship between these characteristics of aphids. The antioxidant enzyme system is more efficient in aphid nymphs, and during aphid development the activity of antioxidant enzymes decreases. The antioxidant enzyme system in aphids appears to deliver effective protection for nymphs and adults under stressful conditions, such as high temperatures.

Multigenerational consequences of aphid size on offspring phenotype and reproduction

AbstractIn many organisms, phenotype and fitness are strongly influenced by both current environmental factors and maternal effects. The low genetic variation, high phenotypic plasticity, and telescoping generations seen in aphids permit us to investigate the relative importance and potential interaction of maternal and current environments on phenotype. Although past studies have identified an influence of maternal host plant on offspring phenotype and reproduction in aphids, few have demonstrated the potential for these maternal effects to also interact with the aphid's current environment. By rearing multiple generations ofAphis nerii(Fonscolombe) (Hemiptera: Aphididae) on their host common milkweed,Asclepias syriaca(L.) (Apocynaceae), we tested the relative influence and interaction of both maternal and current environmental effects of crowding and plant quality on aphid body size and reproduction. Our results indicate that aphid body size increased with current plant quality and decreased with aphid density in both generations, with an additional direct, positive relationship between body size and fecundity. We did not find evidence for adaptive maternal effects, e.g., production of fewer, larger, offspring by stressed mothers. Instead, poor maternal environments constrained aphid body size and reproduction. Importantly, these adverse maternal effects were only seen in offspring where subsequent nymph population growth was allowed to increase unchecked, likely reducing available resources. Our study thus demonstrates that the significance of maternal effects in aphid development and reproduction can depend on current resource availability, shaping the phenotype and fecundity of offspring under stressful conditions. Incorporating this framework for how aphid body size and reproduction respond to current and maternal environments may improve predictions for how aphid population growth is impacted by resource limitation across generations.

Seed priming with calcium chloride enhances wheat resistance against wheat aphid Schizaphis graminum Rondani.

Calcium is an essential macronutrient for plant growth. Although it has been shown that exogenous Ca application can increase plant resistance to abiotic stress, little is known about its potential to enhance plant tolerance to biotic stress. Here, we investigated whether pretreatment of wheat (Triticum aestivum L.) seeds with calcium chloride (CaCl2 ) improves plant resistance against wheat aphid (Schizaphis graminum Rondani). The developmental time, population size, feeding behavior of aphids on plants grown from CaCl2 - and water-pretreated seeds, and plant defense responses to aphid attack were investigated. Seed pretreatment with CaCl2 extended aphid development time and reduced aphid population size and feeding efficiency. In addition, the pretreatment significantly increased the concentration of Ca2+ in wheat leaves, and upregulated expression levels of TaCaM genes and callose synthase genes (TaGSL2, TaGSL8, TaGSL10, TaGSL12, TaGSL19, TaGSL22 and TaGSL23). Callose concentration in the leaves of plants grown from CaCl2 -pretreated seeds increased significantly upon aphid attack. Further, callose deposition was observed mainly in the phloem. These results suggest that seed pretreatment with CaCl2 primes the plant response against wheat aphid attack, leading to modulation of callose deposition in the phloem in response to aphid attack. © 2021 Society of Chemical Industry.

Long-Term Effect of Elevated CO2 on the Development and Nutrition Contents of the Pea Aphid (Acyrthosiphon pisum).

It is predicted that the current atmospheric CO2 level will be doubled by the end of this century. Here, we investigate the impacts of elevated CO2 (550 and 750 μL/L) on the development and nutrition status of the green pea aphid for six generations, which is longer than previous studies. All seven examined physiological parameters were not affected over six generations under the ambient CO2 level (380 μL/L). However, the elevated CO2 levels (550 and 750 μL/L) prolonged nymph duration, decreased adult longevity, female fecundity and protein content, and increased the contents of total lipid, soluble sugar and glycogen. There was a significant interaction between the effect of CO2 levels and the effect of generations on nymph duration, female fecundity and adult longevity. The elevated CO2 had immediate effects on the female fecundity and the contents of total protein, total lipid and soluble sugar, starting within F0 generation. The adult longevity decreased, and the glycogen content increased from the F1 generation. However, the significant effect on the nymph development was only observed after three generations. Our study indicates that the elevated CO2 levels first influence the reproduction, the nutrition and the energy supply, then initiate aphid emergency responses by shortening lifespan and increasing glucose metabolism, and finally result in the slow development under further persistent elevated CO2 conditions after three generations, possibly leading to population decline under elevated CO2 conditions. Our results will guide further field experiments under climate change conditions to evaluate the effects of elevated CO2 on the development of the pea aphids and other insects, and to predict the population dynamics of the green pea aphid.

Effect of RNAi targeting CYP6CY3 on the growth, development and insecticide susceptibility of Aphis gossypii by using nanocarrier-based transdermal dsRNA delivery system

RNA interference (RNAi) has been proved to be a viable method for agricultural pest control. Due to the limited uptake of dsRNA in hemiptera insects, this study used nanocarrier SPc (star polycation) transdermal delivery systems to deliver two truncated fragments (P1/P2) dsRNA of the CYP6CY3 for silencing this target gene in Aphis gossypii. After the cotton aphid was sprayed with the SPc + dsP1/P2 mixture, the expression level of target gene in SPc + dsP1 treatment group was not different from that in dsP1 group at 24 h, 48 h, and significantly lower than that in dsP1 group at 60 h, 72 h, respectively; and the expression level of target gene in SPc + dsP2 treatment group was not different from that in dsP2 group at 24 h, and significantly lower than that in dsP2 group from 48 h, 60 h, 72 h, respectively. In addition, the expression level was continuously silenced after spraying the SPc + dsP1/P2 mixture and significant reduced by 79.7% and 84.3% at 48 h compared with the H2O control group, the mortality rate reached 48.09% and 43.18% at 84 h, respectively. And the cumulative reproduction number of cotton aphids also decreased, but the cumulative death number of newborn nymphs had an increase trend, compared with the control groups. Bioassays after RNAi showed that the silencing of CYP6CY3 increased the susceptibility of the 4th instar aphid to imidacloprid, and increased mortality by 67.21% and 58.69% at 96 h, respectively. The life table parameters of the offspring from the 4th instar cotton aphids from the SPc + dsP1/P2 treatment groups showed that the offspring had a longer pre-reproductive period and post-reproductive period. The intrinsic growth rate was 0.231 ± 0.005, 0.210 ± 0.013 and the finite growth rate was 1.260 ± 0.007 and 1.234 ± 0.016 in the SPc + dsP1/P2 treatment group, these two parameters of the two groups were lower than that of the corresponding control，the population doubling time of the two groups was prolonged and the developmental duration was delayed. These results indicate that CYP6CY3 plays a key role in the growth, development, reproduction and detoxification ability in cotton aphids, and may be as a potential RNAi target for controlling aphids, laying the foundation for the development of new environmentally-friendly RNA pesticides in this field.

Tolerance of an aphid species towards dietary sucrose‐to‐amino acid ratios and recovery from suboptimal nutrition

AbstractAphids feed on the phloem sap of their host plants. The chemical composition of this sap differs between plant species and is modulated by environmental factors. To understand why Myzus persicae (Sulzer) (Hemiptera: Aphididae) is able to infest various plant taxa, we investigated how aphids of this species respond to various sucrose‐to‐amino acid ratios of their diet. Moreover, we studied whether they are able to recover from periods with suboptimal nutrition. Preference and performance bioassays were performed using artificial diets with sucrose‐to‐amino acid ratios of 2.4:1 (optimal ‘control’ diet), 4.8:1 (‘high sucrose’), 1.2:1 (‘high amino acids’), or 1:0 (‘no amino acids’). Also, the capacity to recover from periods on suboptimal diet (i.e., the ‘no amino acids’ diet) was assessed. In four‐choice assays, both nymphs and adults of M. persicae were rarely found on the ‘no amino acids’ diet and they were similarly distributed on the other diets. As long as amino acids were available, the sucrose‐to‐amino acid ratio had only minor effects on aphid development and reproduction. On the suboptimal diet, nymphs survived, but with almost no weight gain over time. After transfer to the ‘control’ diet, they gained weight and reproduced with only low fitness deficits compared to aphids kept on the ‘control’ diet for the whole time. The capacity to survive under suboptimal nutrition and recover from it was dependent on the length of the period on the suboptimal diet. The ability to cope with different dietary sucrose‐to‐amino acid ratios and to withstand suboptimal nutrition for several days may contribute to the broad host plant spectrum of M. persicae and may explain why this species is a serious pest in agricultural systems.

The boom and bust of the aphid's essential amino acid metabolism across nymphal development.

Within long-term symbioses, animals integrate their physiology and development with their symbiont. In a model nutritional mutualism, aphids harbor the endosymbiont, Buchnera, within specialized bacteriocyte cells. Buchnera synthesizes essential amino acids (EAAs) and vitamins for their host, which are lacking from the aphid’s plant sap diet. It is unclear if the aphid host differentially expresses aphid EAA metabolism pathways and genes that collaborate with Buchnera for the production of EAA and vitamins throughout nymphal development when feeding on plants. It is also unclear if aphid bacteriocytes are differentially methylated throughout aphid development as DNA methylation may play a role in gene regulation. By analyzing aphid gene expression, we determined that the bacteriocyte is metabolically more active in metabolizing Buchnera’s EAAs and vitamins early in nymphal development compared to intermediate or later immature and adult lifestages. The largest changes in aphid bacteriocyte gene expression, especially for aphid genes that collaborate with Buchnera, occurred during the 3rd to 4th instar transition. During this transition, there is a huge shift in the bacteriocyte from a high energy “nutrient-consuming state” to a “recovery and growth state” where patterning and signaling genes and pathways are upregulated and differentially methylated, and de novo methylation is reduced as evidenced by homogenous DNA methylation profiles after the 2nd instar. Moreover, bacteriocyte number increased and Buchnera’s titer decreased throughout aphid nymphal development. These data suggest in combination that bacteriocytes of older nymphal and adult lifestages depend less on the nutritional symbiosis compared to early nymphal lifestages.

Heat shock alters pea aphid–Buchnera interactions: negative allometry of gene densities

AbstractIn the face of global climate change, the understanding of how aphid‐symbiont relationships are affected by heat shock is critical. We evaluated the effects of heat shock on the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), and its obligate endosymbiont Buchnera aphidicola Munson et al. by means of quantitative PCR in treated aphids and their offspring. First‐instar aphids received a single heat shock (35 °C for 6 h), repetitive heat shocks (repeat of the single heat shock for 3 days), or a control treatment (constant 20 °C). We evaluated the impacts on aphid body length and Buchnera and aphid gene densities, estimated from the number of copies of bacterial 16S‐rRNA and nuclear elongation factor 1‐alpha (EF1α) genes, respectively. Heat shock negatively affected aphid body length and Buchnera and EF1α gene densities. Heat‐shocked aphids contained lower densities of Buchnera and EF1α genes than control aphids when body length was kept constant. When Buchnera and EF1α gene densities were represented on a log–log scale, Buchnera densities increased with EF1α densities in all treatments, but Buchnera densities showed negative allometry with EF1α densities. Compared to control aphids, heat‐shocked aphids contained lower Buchnera densities relative to EF1α densities. Some heat‐shocked aphids became sterile if their Buchnera gene density was lower than a threshold (ca. 42 000 copies). The offspring of aphids subjected to a single heat shock recovered the number of Buchnera, but the offspring of aphids subjected to repetitive heat shocks exhibited markedly lower Buchnera and EF1α densities. Thus, heat shock negatively affects both aphid and Buchnera cell proliferation, in the heat shock‐treated generation as well as in their offspring, but the impact is more severe on Buchnera. Because the symbiont supplies essential amino acids, vitamins, and an essential protein, this could reduce aphid development and reproduction and possibly leads to extinction of local populations.

Effects of liquid vermicompost and synthetic NPK fertilizer sources on Myzus persicae Sulzer (Aphididae: Hemiptera) fed on tobacco

Green peach aphid (Myzus persicae Sulzer (Aphididae: Hemiptera)) is a polyphagous pest that causes economic losses in the tobacco. In addition to general aphid damage, it is a vector for important viral diseases in tobacco. Fertilization methods, which are used to increased soil fertility, in the plant growing phase, contribute significantly to the optimal physical, chemical and biological properties of the soil, which allows the plants grown in that soil to be more resistant to diseases and pests. Therefore, in this study, the effects of liquid vermicompost and synthetic fertilizer applications on the development and biological parameters of green peach aphids were investigated in comparison with the control. The experiments were carried out under controlled climate chambers. Life table parameters were obtained using the data obtained for the development and reproduction of the aphids. In the study, while there was no statistically significant difference between population parameters, both treatments were found to suppress the pest populations compared to the control application. This application can be used as an ecological control method for the pest.

English

Cabbage aphid, Brevicoryne brassicae is among the notorious insect pests of Canola (Brassica napus) and other Brassica spp., with a reported loss of up to 75%. It has gained resistance against conventional chemical insecticides. So, to activate inducer mediated plant resistance is among the workable solutions against this pest. Henceforth, inducer-mediated resistance based on categorizes of induced-resistance (IR), nutrient-deterrence (ND) and sulphur-integration (SI), was applied in 18 treatments. Their responses against aphid development period, reproduction time, progeny production, immature becoming adults, percent survival and mortalities, were noted-down. In the IR category, all the biological parameters were affected significantly by 1 mM (1 and mM should be in the same line) mM salicylic acid-T4 treatment, whereas in ND, silicon 50 kg ha-1-T10 was more effective. Likewise, during SI studies, bio-sulphur-T15 remained an efficient one. Overall, the developmental period of B. brassicae nymphs was delayed by T10 (Si 50 kg ha-1), followed by T4 (1 mM SA), while Compost-T16 expedited their development. Besides these, reproduction time was reduced at the most by T4, followed by T15. Aphid progeny production was again decreased significantly by T4 and T10, while T16 (Compost) presented the maximum progenies. Associatively, the least number of nymphs becoming adults were shown in T4, T10 followed by T7 (1 mM CA). The highest percent nymph survival was shown in T1 (control) and T16 (compost) with the highest nymph percent mortality in T4 and T7. Hence, salicylic acid, silicon, and bio-sulphur showed maximum effective resistance responses but in concentration-dependent manner. These findings can be used in future integrated pest management programs of aphids and other specialists on related hosts. © 2021 Friends Science Publishers

Insect parasitoid and ant of associated on aphids (Aphididae) colonies on plants in West Java

Aphid is a sucking insect as a pest and vector of virus diseases plants. The aphids presence on plants are often accompanied by ants that symbiotic on aphid’s colony. Mutualism symbiosis between ants and aphids can hinder natural enemies especially parasitoids to parasitizing aphids. This study aims to explore parasitoid and ant species associated with aphids and determine the level of parasitoid parasitization. The survey was conducted on agricultural crops and weeds in West Java area. Samples were taken by purposive sampling looking at the aphid presence, ant, and mummified colonies. Aphid’s identification was carried out at Insect Biosystematics Laboratory, Department of Plant Protection IPB, whileparasitoid and ant identification was carried out at Entomology Laboratory of Zoology LIPI. The identification results obtained four species of Hymenoptera parasitoid, i.e Adialythus ambiguus , Aphidius matricariae , Praon absinthi (Braconidae) and Psyllaephagus pilossus (Encyrtidae) and eight species of ants of Formicidae family, i.e Dolichoderus sp, Dolichoderus thoracicus , Monomorium destructor , Monomorium floricola , Myrmicaria brunnea , Pheidole javana , Polyrhachis dives , and Technomyrmex albipes . The dominant parasitoid species found was A. matricariae , but the highest level of parasitization was P. pilossus (78%), parasites Rhopalosiphum padi in rice plants. Basic information on the types of ants and parasitoid insects associated with aphids can be used in the development of aphids integrated pest management strategies.

Performance and transcriptomic response of the English grain aphid, Sitobion avenae, feeding on resistant and susceptible wheat cultivars

Plant resistance against insects mainly depends on nutrient restriction and toxic metabolites, but the relative importance of nutrition and toxins remains elusive. We examined performance, nutrition ingestion, and transcriptome response of the English grain aphid, Sitobion avenae, feeding on resistant Xiaoyan 22 (XY22) and susceptible Xinong 979 (XN979) wheat cultivars. Aphids had lower body weight and fecundity when feeding on XY22 than on XN979, although the phloem sap of XY22 had a higher nutritive quality (in terms of amino acid:sucrose ratio). Aphids feeding on XY22 also had a lower honeydew excretion rate than those on XN979, suggesting that aphids ingested less phloem sap from XY22. The transcriptome data showed 600 differentially expressed genes (DEGs), and 11 of the top 20 KEGG pathways significantly enriched in DEGs were involved in nutrient metabolism. We found 81 DEGs associated with the metabolism of sugars, lipids, and amino acids, 59 of which were significantly downregulated in aphids feeding on XY22. In contrast, there were 18 DEGs related to detoxifying metabolism, namely eight UDP-glucuronosyltransferases, six cytochromes P450 monooxygenases, one glutathione S-transferase, two ATP-binding cassette transporters, and one major facilitator superfamily transporter; 12 of these were upregulated in the aphids feeding on XY22. Our results indicated that both the quantity and quality of phloem nutrition available to aphids are critical for the growth and development of aphids, and the higher resistance of XY22 is mainly due to the reduction in phloem sap ingested by aphids, rather than toxic metabolites.

Elevated Carbon Dioxide and Nitrogen Impact Wheat and Its Aphid Pest.

The rise in atmospheric carbon dioxide (CO2) generally increases wheat biomass and grain yield but decreases its nutritional value. This, in turn, can alter the metabolic rates, development, and performance of insect pests feeding on the crop. However, it is unclear how elevated CO2 (eCO2) and nitrogen (N) input affect insect pest biology through changes in wheat growth and tissue N content. We investigated the effect of three different N application rates (low, medium, and high) and two CO2 levels (ambient and elevated) on wheat growth and quality and the development and performance of the bird cherry-oat aphid, a major cereal pest worldwide, under controlled environmental conditions. We found that eCO2 significantly decreased total aphid fecundity and wheat N content by 22 and 39%, respectively, when compared to ambient CO2 (aCO2). Greater N application significantly increased total aphid fecundity and plant N content but did not offset the effects of eCO2. Our findings provide important information on aphid threats under future CO2 conditions, as the heavy infestation of the bird cherry-oat aphid is detrimental to wheat grain yield and quality.

Population density of wheat aphid and its natural predators on different wheat varieties planting at different times under ecological zone Sheikhupura, Punjab, Pakisatn

Three year field experiments were conducted to study the population density of wheat aphid and their beneficial fauna on different wheat varieties planted at different times at Adaptive Research Farm Sheikhupura, Pakistan in rice wheat cropping system. The experiment was laid out in split plot design in which varieties were replicated thrice in each planting date. Data for aphid population their predators, meteorological data, yield parameters and grain yield under different planting dates were recorded. Three years results revealed that in this ecological zone for wheat crop the planting dates 10th to 30th November performed better with respect to less attack of aphids, proper days required for maturity, number of grains per spike, number of tillers per m-2, thousand grains weight and grains yield. Late sown planting date causes reduction in yield due to reduce values of yield attributes and attack of aphid at growth stages while early sown date causes reduction in yield due to loss of grains weight by aphid feeding as the climatic conditions favors the development of aphids. Key words: Aphids; Planting dates; Varieties; Wheat; Yield http://dx.doi.org/10.19045/bspab.2020.90189

Simultaneous Increase in CO2 and Temperature Alters Wheat Growth and Aphid Performance Differently Depending on Virus Infection.

Climate change impacts crop production, pest and disease pressure, yield stability, and, therefore, food security. In order to understand how climate and atmospheric change factors affect trophic interactions in agriculture, we evaluated the combined effect of elevated carbon dioxide (CO2) and temperature on the interactions among wheat (Triticum aestivum L.), Barley yellow dwarf virus species PAV (BYDV-PAV) and its vector, the bird cherry-oat aphid (Rhopalosiphum padi L.). Plant traits and aphid biological parameters were examined under two climate and atmospheric scenarios, current (ambient CO2 and temperature = 400 ppm and 20 °C), and future predicted (elevated CO2 and temperature = 800 ppm and 22 °C), on non-infected and BYDV-PAV-infected plants. Our results show that combined elevated CO2 and temperature increased plant growth, biomass, and carbon to nitrogen (C:N) ratio, which in turn significantly decreased aphid fecundity and development time. However, virus infection reduced chlorophyll content, biomass, wheat growth and C:N ratio, significantly increased R. padi fecundity and development time. Regardless of virus infection, aphid growth rates remained unchanged under simulated future conditions. Therefore, as R. padi is currently a principal pest in temperate cereal crops worldwide, mainly due to its role as a plant virus vector, it will likely continue to have significant economic importance. Furthermore, an earlier and more distinct virus symptomatology was highlighted under the future predicted scenario, with consequences on virus transmission, disease epidemiology and, thus, wheat yield and quality. These research findings emphasize the complexity of plant–vector–virus interactions expected under future climate and their implications for plant disease and pest incidence in food crops.

Reduced Mythimna separata infestation on Bt corn could benefit aphids.

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by the Bt trait have increased in importance. It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores. Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn. We compared the performance of Rhopalosiphum maidis feeding on non-Bt corn plants that had been infested by M. separata larvae or were uninfested. The results showed that caterpillar-infested corn plants significantly reduced the fitness of R. maidis leading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera-resistant Bt corn than on non-Bt corn when plants were infested with M. separata, since the caterpillars caused very little damage to the Bt plants. The current findings indicate that reduced M. separata infestation could benefit aphid development in Bt corn. Bt corn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.

Formulation of weather based forecasting model for mustard aphid, Lipaphis erysimi kalt. in Tarai region of Uttarakhand

Lipaphis erysimi (Kalt.) infestation on mustard account for significant yield losses in India. Experimental data from sixteen years were used to study the role of weather on the incidence and development of mustard aphid. Temperature was found to regulate the aphid population build-up and arrival . Weather parameters before one week from aphid population observation contribute higher effect than of the same date, two week prior and three week prior observation. In the present investigation regression equation between aphid incidence and using previous week’s weather data could be used for formulating the forecasting model for L. erysimi, and for taking control measures.