Aphid Density Research Articles

Sugarcane Aphid (Hemiptera: Aphididae) on Sorghum. I. Population Characteristics and Dispersion Patterns in Relation to Different Sample Unit Sizes.

The sugarcane aphid, Melanaphis sacchari (Zehntner), has emerged as a serious pest of sorghum in the United States. Field trials were conducted in Louisiana and South Carolina in 2016-2018 to investigate its population characteristics and distribution patterns in relation to four sample unit sizes (three circular and one leaf based). Sugarcane aphid populations usually progressed through a phase of rapid rise followed by a phase of rapid decline within a span of 5-6 wk, with peak density determined by sorghum cultivars and climatic conditions. Peak population densities for susceptible cultivars were 1.9-14.9× that for resistant cultivars on a per plant basis. Melanaphis sacchari tended to concentrate on the lower green leaf nodes early in the infestation, with the distribution shifting toward higher green leaf nodes as the infestation progressed. Aphid densities per cm2 at the basal and middle sections were about twice as high as at the distal section of leaves. The proportions of infested sample units were fitted to the Wilson-Room binomial model that incorporates the effect of density on clumping pattern. For a specific sample unit size, clumping patterns were similar across cultivars, years, and leaf positions, but varied across infestation stages. For a fixed aphid density per sample unit, the proportion of infested sample units decreased with increasing sample unit size. For a fixed aphid density per cm2, proportion infested increased with increasing sample unit size, indicating less clumping with a larger sample unit size. Field sampling time and efficiency between samplers were quantified.

Altering Planting Date to Manage Melanaphis sacchari (Hemiptera: Aphididae) Populations in Sweet Sorghum.

Melanaphis sacchari Zehntner is a new pest of sweet sorghum in the United States, with the potential to cause complete crop failure. In Kentucky, sweet sorghum is normally planted in early May and harvested in late August or September. Planting sweet sorghum earlier in the season may avoid damaging levels of M. sacchari that develop in late summer. In a 2-yr field study, three different planting dates separated by a month (April, May, and June) were tested for their effect on M. sacchari densities and sweet sorghum yield. April (early) planted sweet sorghum was grown in greenhouses and transplanted to the field. May (mid) and June (late) planted sweet sorghum were direct seeded in the field. Melanaphis sacchari population densities were evaluated weekly starting in June. Sweet sorghum was harvested at the onset of the hard dough stage. Plots were split into two subplots, insecticide or noninsecticide, in the second year to control for planting date effect on yield. Early-planted sweet sorghum had lower aphid densities, but had lower yield relative to mid-planting date, which had the highest yield. Insecticide drenches in 2019 reduced cumulative aphid days in mid-plantings and late plantings, but did not significantly affect yield within planting dates. Seeding sweet sorghum earlier can reduce M. sacchari densities; however, this method alone may not provide the highest yields. We documented that the recommended planting date (May) for Kentucky produced the highest yield.

Zucchini Plants Alter Gene Expression and Emission of (E)-β-Caryophyllene Following Aphis gossypii Infestation.

Zucchini (Cucurbita pepo L.) is widely cultivated in temperate regions. One of the major production challenges is the damage caused by Aphis gossypii (Homoptera: Aphididae), a polyphagous aphid, which can negatively affect its host plant, both directly by feeding and indirectly by vectoring viruses. To gain insights into the transcriptome events that occur during the zucchini–aphid interaction and to understand the early-to-late defense response through gene expression profiles, we performed RNA-sequencing (RNA-Seq) on zucchini leaves challenged by A. gossypii (24, 48, and 96 h post-infestation; hpi). Data analysis indicated a complex and dynamic pattern of gene expression and a transient transcriptional reconfiguration that involved more than 700 differentially expressed genes (DEGs), including a large number of defense-related genes. The down-regulation of key genes of plant immunity, such as leucine-rich repeat (LRR) protein kinases, transcription factors, and genes associated with direct (i.e., protease inhibitors, cysteine peptidases, etc.) and indirect (i.e., terpene synthase) defense responses, suggests the aphid ability to manipulate plant immune responses. We also investigated the emission of volatile organic compounds (VOCs) from infested plants and observed a reduced emission of (E)-β-caryophyllene at 48 hpi, likely the result of aphid effectors, which reflects the down-regulation of two genes involved in the biosynthesis of terpenoids. We showed that (E)-β-caryophyllene emission was modified by the duration of plant infestation and by aphid density and that this molecule highly attracts Aphidius colemani, a parasitic wasp of A. gossypii. With our results we contributed to the identification of genes involved in cucurbit plant interactions with phloem feeders. Our findings may also help pave the way toward developing tolerant zucchini varieties and to identify molecules for sustainable management of harmful insect populations.

Biological control of Aphis spiraecola in apples using an insectary plant that attracts and sustains predators

Habitat management, such as adding insectary plants to agroecosystems, is a useful technique for biological control. It can improve pest control through natural enemy augmentation and conservation. We evaluated use of the insectary plant Cnidium monnieri (L.) Cuss. to increase the diversity and population density of natural enemies, promote the movement of natural enemies, and improve suppression of the spirea aphid (Aphis spiraecola Patch). An apple orchard experiment included C. monnieri as the treatment and the absence of C. monnieri as the control. The results suggested that C. monnieri can foster predatory natural enemies, such as Propylaea japonica, Harmonia axyridis, Hippodamia variegata, Chrysoperla sinica, and Episyrphus balteata. Density of the predators on the apple trees in the treatment was significantly higher than in the control. Density of spirea aphids on the apple trees in the treatment was significantly lower than in the control. Rubidium (Rb) was used as a tracking marker transferred along the food chain of C. monnieri (4.08 μg/ml) – celery aphid (Semiaphis heraclei) (0.46 μg/ml) – lady beetle (0.51 μg/ml) in a laboratory experiment. The highest Rb content in a lady beetle (0.62 μg/ml) was found 3 days after marking. Combined with field sampling and Rb marking, the results showed that 24.2% and 42.7% of H. axyridis on the apple trees moved from the insectary plant C. monnieri in 2018 and 2019, and that 53.2% and 48.4% of C. sinica on the apple trees transferred from C. monnieri in 2018 and 2019. The insectary plant C. monnieri attracts and fosters predatory natural enemies, which then move to the apple trees and suppress spirea aphids. These findings illustrate an effective method for enhancing biological control of aphids in apple orchards.

The Effect of Planting Dates and Nitrogen Fertilizer on Aphis craccivora (koch) Infestation in Faba Bean (Vicia faba, L.) fields

The present study was carried out at Wadi El Natrun district, El-Behera Governorate during season 2019–2020. In a field study, the effect of two planting dates and three rates of nitrogen fertilizer on a population of Legume aphid, Aphis craccivora (Koch) (Homoptera: Aphididae), in faba bean (Vicia faba, L.)were investigated. The results show that the higher occurrence of the aphid was recorded on the early planting date than the recommended one. The combination effect of climatic factors and plant age on aphid population density was presented as explained variance which was 75 and 74% in the early and recommended planting dates respectively. The population densities of aphid were significantly lower on faba bean plants fertilized with the lowest rate of nitrogen fertilizer (75 kg feddan−1), compared with those fertilized with recommended and highest rate (100 and 125 kg feddan−1 respectively) in both early and recommended planting dates. These results indicate that the recommended planting date and moderately plant nutrition can help plants to avoid insect pests infestation.

Proteome changes in pepper (Capsicum annuum L.) leaves induced by the green peach aphid (Myzus persicae Sulzer)

BackgroundAphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism. Pepper (Capsicum annuum L.) leaf proteomic response against Myzus persicae (Sulzer) has been investigated and analyzed by LC-MS/MS coupled with bioinformatics tools.ResultsInfestation with an initially low density (20 aphids/plant) of aphids restricted to a single leaf taking advantage of clip cages resulted in 6 differentially expressed proteins relative to control leaves (3 proteins at 2 days post-infestation and 3 proteins at 4 days post-infestation). Conversely, when plants were infested with a high density of infestation (200 aphids/plant) 140 proteins resulted differentially expressed relative to control leaves (97 proteins at 2 days post-infestation, 112 proteins at 4 days post-infestation and 105 proteins at 7 days post-infestation). The majority of proteins altered by aphid attack were involved in photosynthesis and photorespiration, oxidative stress, translation, protein folding and degradation and amino acid metabolism. Other proteins identified were involved in lipid, carbohydrate and hormone metabolism, transcription, transport, energy production and cell organization. However proteins directly involved in defense were scarce and were mostly downregulated in response to aphids.ConclusionsThe unexpectedly very low number of regulated proteins found in the experiment with a low aphid density suggests an active mitigation of plant defensive response by aphids or alternatively an aphid strategy to remain undetected by the plant.Under a high density of aphids, pepper leaf proteome however changed significantly revealing nearly all routes of plant primary metabolism being altered. Photosynthesis was so far the process with the highest number of proteins being regulated by the presence of aphids.In general, at short times of infestation (2 days) most of the altered proteins were upregulated. However, at longer times of infestation (7 days) the protein downregulation prevailed.Proteins involved in plant defense and in hormone signaling were scarce and mostly downregulated.

Impact of natural products on Acyrthosiphon pisum density on Pisum sativum L. and forage quality

A field trial was conducted at the Institute of Forage Crops (Pleven, Bulgaria) from 2015 to 2017. It studied the effects of natural products on Acyrthosiphon pisum density, as well as changes in the chemical composition, content of plant fibre components and enzyme degradability in forage pea. Treatments with the natural insecticides Madex and Agricolle, applied alone or in combination with the organic fertilizers Lithovit and Nagro were performed twice - at the beginning of the flowering stage and one week later. The fertilizers used in the trial are environmentally safe and approved for use in organic production. The synthetic products Kristalon, a foliar fertilizer, and Proteus 110 OD, an insecticide, were used for comparison. The application of natural products, either alone and in combination, resulted in a reduction in pea aphid density. Applying Agricolle with Nagro, followed by Lithovit with Agricolle, led to the highest aphid number decrease (70.0 and 51.1%, respectively). An optimal combination of decrease in the content of plant cell wall fibre components, cellulose and lignification degree with a significant increase in forage in vitro enzyme digestibility was established after applying Agricolle with Lithovit and Agricole with Nagro. Digestibility reached 71.8 and 69.8%, respectively, an increase of 8.2-5.2%, while ADF, cellulose and lignification degree decreased from 7.1 and 7.7%, 8.0 and 23.4%, amd 10.5 and 6.8% after applying Agricolle with Lithovit and Agricole with Nagro, respectively. In comparison, the synthetic products Kristalon and Kristalon with Proteus increased forage quality, but to a relatively lesser extent. A stronger linear relationship was found between aphid density and dry matter digestibility, compared to the content of neutral detergent fibres. Pea forage with low content of plant cell wall fibre components, cellulose and lignification degree, high protein content, and digestibility after treatment with the natural product Agricolle, and its combinations with Lithovit and Nagro, make it a very good complement to other forages in dairy cow rations.

The age of tomato plants affects the development of Macrosiphum euphorbiae (Thomas, 1878) (Hemiptera) colonies

We tested the hypothesis that the intensity and duration of Macrosiphum euphorbiae infestations in tomato depend on both the age (phenological stage) of the host plant and the initial number of aphids present in the colony. We compared the effects of three initial levels of infestation and two phenological stages of the plant (pre-flowering and flowering stages) on infestation curves. The position of the infestation peak over time was significantly affected by the plant phenological phase. Populations of M. euphorbiae reached the highest peak of abundance on plants infested at the pre-flowering stage compared to those subsequently infested. Within a phenological phase, the maximum abundance also varied according to the initial aphid density on the plant. The implications concerning the management of the pest in the field are briefly discussed

SEASONAL MONUMENTAL INSECTS ACCOMPANYING EUPHRATES POPLAR LEAVES

The study was conducted in the poplar field belonging to the Department of Plant Protection, College of Agriculture and Forestry, University of Mosul in the autumn season of 2018-2019, where it was found that the leaves of the Euphrates poplar have more than one type of insect that infects the leaves, including Egerirotriaza cardi (Berg.) (Psyllidae, Homoptera) poplar leaves, this was evidenced by the symptoms of the infection it causes, which are spotting and galls. The highest infection was recorded in the first week of January 2019, with an average of (70.71) symptoms reported, and the highest average infection was recorded on the eastern side with an average of (41.23) symptoms, although the study showed the highest average of the spots resulting from the infection reached (95.33) spot recorded in the first week of January 2019, on the upper and lower surface of leaves on the western side of the tree, while the highest average of (26.33) galls was recorded on the upper surface of the leaf from the southern side in the last week of January 2019, on the upper and lower surface of the leaves and on the western side of the tree, while the highest average of (26.33) galls was recorded on the upper surface of the leaf from the southern side in the last week of January 2019, where the study showed that there is a negative significant correlation between the temperatures of that autumn season with The insect numerical density (-0.747) at a significant level (p<.0001), this is due to the low temperatures for the period from 4/12/2018 to 23/1/2019, which ranged between (13.8 - 7.11 ° C), while the relative humidity averages did not have a significant correlation with the insect's numerical density, which ranged between (51.43 - 61.14%).

Turunçgil yaprakbitleri (Hemiptera: Aphididae): bulaşıklık oranları, popülasyon dalgalanmaları, konukçu bitki ve yaş tercihleri

Citrus plantations are suffered from many different pest species in East Mediterranean Region. Among them, aphids (Hemiptera: Aphididae) are one of the important groups. Some species such as Aphis gossypii Glover, Aphis spiraecola Patch, Aphis craccivora Koch, Aphis (Toxoptera) aurantii (Boyer de Fanscolombe) and Myzus (Nectarosiphon) persicae (Sulzer) (Hemiptera: Aphididae) cause harm especially young citrus orchards. This study aimed to investigate regional distribution, seasonal fluctuation, host and host age preferences within citrus species of these aphid species in 15 sub-regions from Adana, Hatay, Osmaniye and Mersin between 2007 and 2009. While the mandarin was more preferred than other citrus species, grapefruit was the least preferred citrus species among in all the three provinces. Among the citrus species in the Mersin region, A. spiraecola was the most common in lemons, while A. (T.) aurantii preferred mandarin compare to others. In Adana and Hatay regions, mandarin was the most preferred citrus species for all aphid species except M. (N.) persicae. Aphid preferences depending on the age showed differences in citrus age scale by region. A. (T.) aurantii, on the other hand, had the highest rate of presence between the ages of 11-20 in Hatay and between the ages 21-40 in Mersin. The prevalence of citrus varieties in Adana and Hatay parallelly affected the distribution of aphids. However, A. spiraecola was dominant aphid species on the lemon. Adana, which has a richer flora compared to Mersin and Hatay regions, has been determined the highest aphid density in different species. The fact that Aphis goosypii and A. spiraecola create up to 30-40% infections rate in citrus orchards not only in spring, but also in July, and intense again in autumn have made these pests harmful for four seasons.

Comparison of biological methods to control Aphis fabae Scopoli (Hemiptera: Aphididae) on kalanchoe crops in East Africa

Aphids cause considerable damage to numerous crops all over the world and insecticides are the main means of controlling them, despite their detrimental impacts on human and environmental health. This study assessed the effectiveness of the parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae), a mixture of predatory ladybird beetles, Hippodamia variegata Goeze, Chilocorus calvus Chiccl, and Cheilomenes propinqua Mulsant (Coleoptera: Coccinellidae), and an entomopathogenic strain of Aspergillus flavus Link (Eurotiales: Trichocomaceae), collected locally in Tanzania, to control Aphis fabae Scopoli (Hemiptera: Aphididae). After assessing the predation and parasitism rates of these natural enemies at different aphid densities in laboratory experiments, their ability to control aphids on kalanchoe was assessed in a greenhouse experiment over two seasons. The largest number of A. fabae parasitized or consumed in the laboratory was found at a density of 160 aphids per predator, or parasitoid. At that density, an adult female of A. colemani parasitized 114 A. fabae per day, on average, and adults of C. calvus, H. variegata, and C. propinqua consumed 75, 72, and 85 aphids per day, respectively. A. flavus spores applied at 1 × 107 spores ml−1 reduced the aphid population by 7.9 and 12.6 times within 10 days in the first and second seasons of the greenhouse experiments, respectively, as opposed to 2.8 and 2.5 times by releasing a mixture of the ladybirds at a rate of 5 adults/m2, and by 3.3 and 9.5 times by releasing A. colemani at a rate of 2 adults/m2. This study confirmed the potential of these locally collected bio-control agents for controlling A. fabae. However, use of the isolated A. flavus strain was undermined by its production of aflatoxin. Further research is therefore required to tap into the potential of a non-toxic strain of A. flavus and/or other entomopathogenic fungi.

Population Fluctuation of Cotton Aphid (Aphis gossypii Glover) on Roselle Plants in Relation with Certain Biotic and Abiotic Factors

This research work was conducted to describe the relationship between the population density of the cotton aphid on roselle plants and its accompanied predators, some quantities characters of roselle plants and the main weather factors at Awlad – Sakr district, Shakira Governorate, Egypt in 2018 and 2019 growing seasons. Aphids were collected by using plant sample technique. Results indicated that A. gossypii showed seven peaks of activity, the highest one ( 1453 individuals /sample) was on the 8 th of August in the first season. In the second season A. gossypii recorded five distinct activity peaks the highest of them took place on the 23 rd of July with 5068 individuals /sample. Simple correlation, partial regression and coefficient of determination between aphid population and the aforementioned factor were evaluated. Statistical analysis results showed that these factors played a conspicuous role in detecting the activity of cotton aphid during the two investigated seasons of the study.

Where are the basal fungi? Current status on diversity, ecology, evolution, and taxonomy

To date, the majority of mycological studies are focused on Ascomycota and Basidiomycota. Research on basal fungi is rather limited with an obvious scarcity of data. Classification of basal fungi has witnessed ongoing changes in the last few decades. There have been numerous taxonomic revisions, establishment of new phyla and debates on the possibility to exclude some basal lineages from the currently circumscribed fungal groups. Zoosporic phyla such as Rozellomycota, Aphelidiomycota and Chytridiomycota are characterized by zoospores, which are motile spores with a flagellum. The position of the first two within the fungal kingdom is currently being debated. Non zoosporic phyla are collectively called zygomycetous fungi and include Mucoromycota and Zoopagomycota. Basal fungi perform important ecological roles. Some groups of basal fungi control the population density of plankton, Oomycetes, aphids, and small invertebrates, while taking part in recycling of energy and matter in food webs. A few basal fungi are known for uptaking toxic heavy metals from the environment. The earliest basal fungi emerged just after the divergence of the nucleariid line of phagotrophs. Various taxonomic studies question the monophyly of some basal phyla, such as Chytridiomycota. Depending on the life mode of the fungi and whether motile or non-motile spores are produced, the isolation methods differ. For the culture of parasitic zoosporic fungi, co-culturing the fungi with their host is recommended while for saprobes ones, baits can be used. For zygomycetous fungi, common methods include dilution plating and direct inoculation. In this review, we pinpoint research gaps and discuss the current classification schemes along with information on evolution, diversity, current methods and challenges to isolate and culture basal fungi.

Age-dependent functional response of Aphidius matricariae (Hymenoptera: Braconidae) on tobacco aphid, Myzus persicae nicotianae (Hemiptera: Aphididae)

• Functional response of A. matricariae was affected by the parasitoid’s age. • The searching efficiency of A. matricariae was declined with increasing age. • The highest efficiency of A. matricariae gained in the first three days of life. This study was performed to investigate the age-dependent functional response of Aphidius matricariae Haliday (Hymenoptera: Braconidae) at varying densities of tobacco aphid, Myzus persicae nicotianae Blackman (Hemiptera: Aphididae). Six densities (2, 4, 8, 16, 32, and 64 numbers) of third instar nymphs of M. persicae nicotianae were daily exposed to one pair of 1-day-old A. matricariae until the parasitoid female died. Each host aphid density was replicated 10 times. The experiments were conducted at constant environmental conditions (25 ± 1 °C, 70 ± 5% RH and 16:8h L:D photoperiod). The logistic regression model demonstrated that the functional response of A. matricariae was type III in the second day and type II in the first day and from third to the end of adult parasitoid lifetime. The handling time ( T h ) was lowest in the first day (0.2305 h) and highest in the sixth day (2.9296 h) of the parasitoid’s life. The searching efficiency ( a ) values were 0.0573, 0.0649, 0.0503, 0.0229, and 0.0077 h −1 in the first, third, fourth, fifth, and sixth days of the parasitoid’s life, respectively. Also, the b value for type III functional response was 0.0147 in the second day. The values of maximum attack rate ( T / T h ) ranged from 104.12 nymphs/24 h in the first day to 19.8 nymphs/24 h in the sixth day of parasitoid’s life. Based on the results, A. matricariae showed a high potential to control the population of tobacco aphid and the highest efficiency gained in the first half of the female parasitoid life.

Effects of Aphid Density and Plant Taxa on Predatory Ladybeetle Abundance at Field and Landscape Scales.

Simple SummaryIn agroecosystems, predatory ladybeetles play an important role in suppressing aphid populations. How ladybeetles make use of host plant diversity in multicropping landscapes has rarely been documented in China. In this study, we examined the relationship between aphid densities and ladybeetle densities at both the local field and landscape scales. Overall, we found that there was a positive correlation between aphid densities and ladybeetle densities. However, plant taxa had no significant influence on predatory ladybeetle abundance at the local field scale. In addition, the effect of aphids on ladybeetles abundance was influenced by the crop type and growing season at the regional landscape scale. There was a significant positive correlation between aphid and ladybeetle populations on cotton only in July and August, whereas the correlation was significant for maize throughout the whole growing season. The δ13C value indicated that most prey aphids for ladybeetles originated from crops where aphids are abundant (cotton in June and July; both maize and cotton in August). These findings improved our understanding of the migration and dispersal of ladybeetles among different habitats and plant species and provided insight into the promotion of regional conservation and pest control of natural enemies in Northern China.In agroecosystems, predatory ladybeetles play an important role in restraining aphid population growth and suppressing aphid populations. They can adapt to various habitats and make use of various aphid species associated with multiple host plants during their life cycle. Agricultural landscapes in China are composed of a mosaic of small fields with a diverse range of crops, and how ladybeetles make use of host plant diversity in such landscapes has rarely been documented. In this study, we examined the relationship between aphid densities and ladybeetle densities in two different settings: (i) on the majority of plant species (including crops, trees, and weeds) at a local field scale in 2013 and 2014, and (ii) in paired cotton and maize crop fields at a regional landscape scale in 2013. Overall, we found that aphid abundance determined predatory ladybeetle abundance at both the local field and landscape scales, and there was a positive correlation between aphid densities and ladybeetle densities. However, plant taxa had no significant influence on the predatory ladybeetle abundance at the local field scale. In addition, the effect of aphids on ladybeetles abundance was influenced by the crop type and growing season at the regional landscape scale. There was a significant positive correlation between aphids and ladybeetles populations on cotton only in July and August, whereas the correlation was significant for maize throughout the whole growing season. We also conducted an analysis of the stable carbon isotope ratios of the adult ladybeetles caught in cotton and maize fields (C3 and C4 crops, respectively) in a regional landscape-scale survey in 2013. The δ13Cvalue indicated that most prey aphids for ladybeetles originated from crops where aphids are abundant (cotton in June and July; both maize and cotton in August).These findings improved our understanding of the migration and dispersal of ladybeetles among different habitats and plant species and provided insight into the promotion of the regional conservation and pest control of natural enemies in northern China.

Phytochemistry-mediated disruption of ant-aphid interactions by root-feeding nematodes.

Plants link interactions between aboveground and belowground organisms. Herbivore-induced changes in plant chemistry are hypothesized to impact entire food webs by changing the strength of trophic cascades. Yet, few studies have explored how belowground herbivores affect the behaviors of generalist predators, nor how such changes may act through diverse changes to the plant metabolome. Using a factorial experiment, we tested whether herbivory by root-knot nematodes (Meloidogyne incognita) affected the aboveground interaction among milkweed plants (Asclepias fascicularis or Asclepias speciosa), oleander aphids (Aphis nerii), and aphid-tending ants (Linepithema humile). We quantified the behaviors of aphid-tending ants, and we measured the effects of herbivore treatments on aphid densities and on phytochemistry. Unexpectedly, ants tended aphids primarily on the leaves of uninfected plants, whereas ants tended aphids primarily at the base of the stem of nematode-infected plants. In nematode-infected plants, aphids excreted more sugar per capita in their ant-attracting honeydew. Additionally, although plant chemistry was species-specific, nematode infection generally decreased the richness of plant secondary metabolites while acting as a protein sink in the roots. Path analysis indicated that the ants' behavioral change was driven in part by indirect effects of nematodes acting through changes in plant chemistry. We conclude that belowground herbivores can affect the behaviors of aboveground generalist ant predators by multiple paths, including changes in phytochemistry, which may affect the attractiveness of aphid honeydew rewards.

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

Phytohormone responses in pepper (Capsicum annuum L.) leaves under a high density of aphid infestation.

The time course response of selected phytohormones has been evaluated in sweet pepper plants (Capsicum annuum L.) submitted to a high density (200 aphids/plant) of aphid (Myzus persicae Sulzer) infestation. Abscisic acid (ABA), salicylic acid (SA), indole-3-acetic acid (IAA), and jasmonates (JAs), including jasmonic acid (JA), jasmonoyl-l-isoleucine (JA-Ile), and cis-OPDA have been simultaneously identified and quantitated by UHPLC-MS/MS in pepper leaf tissue harvested at 3, 8 hours post-infestation (hpi), 1, 2, 4 and 7 days post-infestation (dpi). Infested plants showed a reduction in stem length at 7 dpi and in the number of leaves and leaf width from 4 dpi onwards. JA and JA-Ile significantly increased very early (from 3 hpi) while SA only accumulated at 7 dpi. Despite the high density of infestation, the aphid-induced accumulation of JAs was much lower than the burst typically induced by chewing herbivores. On the other side, ABA peaked in aphid-infested plants at 2 and 4 dpi, while IAA content did not change significantly at any time point. Growth inhibition may be partially explained by the high levels of JAs found in aphid-infested plants. The possibility that the obtained results support the hypothesis of the aphid manipulation of plant metabolism is discussed.

Efficiency of the convergent ladybird beetle Hippodamia convergens against the legume aphid Aphis craccivora in laboratory and semi-felid conditions.

Laboratory and semi-field studies were conducted to investigate some biological parameters, feeding capacity and releasing efficiency of Hippodamia convergens on legume aphid, Aphis craccivora. At 25±2˚C and 65±5 R.H., durations of the eggs' incubation period, the four larval instars and pupae were 4.48, 2.11, 2.23, 2.23, 2.68 and 4.39 days, respectively. The average feeding of the 4th instar larvae fed on 84.47 aphids of 4th nymphal instar, being the highest voracious feeder compared to the first three larval instars which consumed the means of 14.4, 21.3 and 32.87 individuals, respectively. When fed on A. craccivora nymphs, female survived longer (50.83 days) than male (34.73days), a single H. convergens female deposited average total of 455.13eggs. The semi-field studies evaluated the controlling capacity against infestation by A. craccivora on faba bean seedlings by H. convergens released under greenhouse conditions, as; only adults, only 3rd instar larvae and both stages. Either of the three treatments for releasing Hippodamia caused reductions of aphid densities than control. In experiment one; 3, 9 and 15 adults/plot were released only one time. Ten days after release, the treatment receiving 15 adults/plot showed the highest reduction rate in aphids (100.00%) compared to that received 3adults (86.78 %) or 9 adults (95.41%) /plot. In the second treatment; 3, 9 and 15 larvae/plot were released one week after infestation, reduction rate of 96.93% occurred 10 days after releasing of15 larvae/plot. In the third experiment; both stages altogether were released at 3 ratios, i.e., 1adult:2 larvae, 3 adults:6 larvae and 5adults: 10larvae/plot. The highest reduction rate (99.14%) of A. craccivora occurred by the third treatment (5A:10L/plot) after 13 days from the releasing date. Treatment receiving only adults showed the highest reduction rate of A. craccivora densities compared to the two other treatments. Accordingly, releasing H. convergens adults only was better than the other two treatments for control of A. craccivora infestations.

Field Screening of Seven Cultivars of Cabbage Against Cabbage Butterfly (Pieris brassicae) and Cabbage Aphids (Brevicoryne brassicae) at Gkuleshor, Baitadi, Nepal

Field screening of seven cultivars of cabbage namely: Green Crown, Green Top, Green Coronet, Pioneer, Nepa Round, Copenhagen Market and Golden Acre were carried out against cabbage butterfly (Pieris brassicae) and cabbage aphid (Brevicoryne brassicae) at the research farm of entomology section, Gokuleshwor Agriculture and Animal Science College, Baitadi in RCBD design from October 2017 to February 2018. Five plants were tagged randomly after transplanting in field excluding border plants in each plot. Data were collected for the population dynamics of cabbage butterfly larvae and cabbage aphid on weekly basis. None of the seven cultivars were found resistant to cabbage butterfly and cabbage aphid, however their population density varied on tested cultivars. Cabbage butterfly population was recorded the highest on the cultivar Pioneer (22.88 larvae/plant) and the lowest on the cultivar Copenhagen Market (10.06 larvae/plant), and other cultivars were of intermediate types. Similarly, the population density of aphid ranged from 36.70 to 105.58 aphids/leaf. The highest population density of aphid was recorded on cultivar Green Crown (105.58 aphids/leaf) and the lowest on cultivar Copenhagen Market (39.82 aphids/leaf. From the results, Copenhagen Market proved to be the best against both cabbage butterfly and cabbage aphids.