Aphid Counts Research Articles

New okra genotypes for the management of aphids (Hemiptera: Aphididae) in the diverse ecological landscapes of Central Africa.

Various aphid species, including Aphis gossypii Glover (Hemiptera: Aphididae), are considered important pests of okra and other vegetables. Previous studies under 1 environment in Cameroon, Central Africa, had found multiple okra genotypes with resistance to A. gossypii. However, the stability and yield performance of the "resistant" genotypes across different environments were unknown. Ten previously identified aphid-resistant okra genotypes along with 1 commercial variety and a local landrace (specific to a given location) were compared during 2 seasons in replicated trials in 4 agro-ecological zones of Cameroon that also represent large areas of Central Africa. Aphid populations and okra yield parameters were evaluated. Breeding values were predicted using a linear mixed model for all data, and genotypes by location interactions were identified. The area under the infestation pressure curve (AUIPC) was calculated using aphid count data and subjected to resistance analysis. The Local-the most susceptible with the highest breeding value (+2.33)-and VI060794-one of the moderately resistant-genotypes had the highest yield per hectare. The only resistant genotype VI036213 had the lowest breeding value (-2.20). Genotype × location interactions were significant for yield, pod width, and plant height, while location variance was significant for all parameters evaluated. When considering that higher aphid densities could lead to greater pesticide use and, therefore higher production and environmental costs, the high-yielding VI060794-with moderate aphid resistance across multiple environments-presents an alternative or substitute for local landraces across multiple agro-ecologies of Cameroon and (by extension) Central Africa.

Semi‐natural habitat, but not aphid amount or continuity, predicts lady beetle abundance across agricultural landscapes

Abstract The amount of semi‐natural habitat surrounding farm fields is a common but inconsistent predictor of natural enemy populations and predation services. Standard land cover metrics may not accurately capture the actual availability of limiting resources for natural enemies and can miss important dynamics across space and time. Theory from animal movement and landscape ecology predicts that regions with more, spatio‐temporally continuous resources (i.e. food and shelter) should have larger predator populations and enhanced biological control. To test these predictions empirically, we designed a study measuring aphids, lady beetles and predation services in agricultural landscapes in Wisconsin, USA. In two study years, we sampled lady beetles and aphids in 336 crop fields (corn, soybean, alfalfa and small grains) and adjacent semi‐natural habitat patches (grasslands and woodlands) across 24 1.5 km buffer landscapes at four to seven time points each, and in 1 year, we assessed predation rates with sentinel egg cards. We used aphid counts to model habitat‐specific aphid phenologies, from which we calculated landscape indices of prey amount and continuity. These indices, along with semi‐natural habitat area, were used to predict lady beetle abundance. While there were strong differences in the abundance and timing of aphids by habitat, semi‐natural habitat amount was still a better predictor of lady beetle counts and sentinel egg predation than either aphid amount or continuity indices in these landscapes. Synthesis and applications. Our findings confirm the robust relationship between lady beetles and semi‐natural habitat in agricultural landscapes, and highlight the complexities of measuring fine‐scale resource heterogeneity in real landscapes. Retaining or adding woodland and grassland patches in agricultural landscapes is likely to support larger lady beetle populations and enhance predation in crop fields. Our results suggest that these habitats may be more important for shelter than prey continuity, though this mechanism warrants further investigation. Future work should continue to refine experimental methods for the successful integration of landscape ecology and animal behaviour to support conservation goals.

Efficacy of Plant Extracts for the Control of Pepper Insect Pest (Green Peach Aphid (Myzus persicae L.)

Aphids pose significant threats to crop productivity, necessitating effective and sustainable pest management strategies. This study investigated the repellent properties of neem and papaya leaf extracts on green peach aphids and the impact of the extracts on plant growth in pepper (Capsicum spp.). The experiment involved 7 treatments and 3 treatment replications with varying concentrations of neem and papaya extracts (6.5 v:v, 7.5 v:v, and 8.5 v:v) compared to a control group (Distilled water). The Randomized Complete Block Design (RCBD) was used as an experimental design. The study site was Cuttington University’s College of Agriculture Research site. The distances between plots and blocks were 0.6 m and 1 m, correspondingly. In the laboratory bioassay, results uncovered distinct trends, with the control treatment exhibiting the highest mean aphid count (41.0), while neem 8.5 v:v (6.0) and papaya 8.5 v:v (8.1) treatments established substantial effectiveness in reducing aphid populations. The highest mean aphid counts following biopesticidal application were 48.0 and 76.7 after 1 and 2 weeks, respectively and were recorded in the untreated control plots, while the lowest mean aphid counts were 21.3 and 6.0 after 1 and 2 weeks, respectively. Furthermore, neem 8.5 v:v treatment consistently showed the highest mean values across plant height (16.2 cm), leaf length (8.2 cm), leaf width (5.2 cm), and repellency index (3.0), indicating potential positive impacts on plant growth and repellency. Untreated control measured the lowest values for plant height (13.8 cm), leaf length (6.0 cm) and repellency index (1.0). The study demonstrated the potential of both extracts to suppress aphid populations and enhance plant growth. Applying these natural extracts as part of an integrated pest management (IPM) strategy can be beneficial for controlling aphid infestations in pepper crops. Their use as repellents can reduce aphid populations, minimizing potential crop damage and yield losses.

Developing a hybrid convolutional neural network for automatic aphid counting in sugar beet fields

Aphids can cause direct damage and indirect virus transmission to crops. Timely monitoring and control of their populations are thus critical. However, the manual counting of aphids, which is the most common practice, is labor-intensive and time-consuming. Additionally, two of the biggest challenges in aphid counting are that aphids are small objects and their density distributions are varied in different areas of the field. To address these challenges, we proposed a hybrid automatic aphid counting network architecture which integrates the detection network and the density map estimation network. When the distribution density of aphids is low, it utilizes an improved Yolov5 to count aphids. Conversely, when the distribution density of aphids is high, it switches to CSRNet to count aphids. To the best of our knowledge, this is the first framework integrating the detection network and the density map estimation network for counting tasks. Through comparison experiments of counting aphids, it verified that our proposed approach outperforms all other methods in counting aphids. It achieved the lowest MAE and RMSE values for both the standard and high-density aphid datasets: 2.93 and 4.01 (standard), and 34.19 and 38.66 (high-density), respectively. Moreover, the AP of the improved Yolov5 is 5 % higher than that of the original Yolov5. Especially for extremely small aphids and densely distributed aphids, the detection performance of the improved Yolov5 is significantly better than the original Yolov5. This work provides an effective early warning caused by aphids in sugar beet fields, offering protection for sugar beet growth and ensuring sugar beet yield. The datasets and project code are released at: https://github.com/JunfengGaolab/Counting-Aphids.

Bioefficacy of Tagetes minuta L. against Aphis craccivora Koch (Hemiptera, Aphididae)

Efficacy of solvent fractions of Tagetes minuta L. (hexane, chloroform and aqueous fractions of aerial parts) was evaluated against Aphis craccivora Koch at five different concentrations (0.025, 0.05, 0.1, 0.15 and 0.2%) in the laboratory. At higher concentrations, all the fractions recorded significant reduction in aphid count; maximum reduction after 120h of treatment was in hexane fraction at 0.2 per cent (90.00%), followed by chloroform fraction at 0.2 per cent (86.67%) and aqueous fraction at 0.2 per cent (85.00%). The best concentrations of the three solvent fractions of T. minuta identified in the laboratory were evaluated against the aphid on cowpea, in a pot culture experiment. By 10th day of treatment, all the fractions at 2 per cent concentration reduced population of aphids, with the highest reduction in hexane fraction.

Economic-threshold-based classification of soybean aphid, Aphis glycines, infestations in commercial soybean fields using Sentinel-2 satellite data

The soybean aphid (SBA), Aphis glycines Matsumura (Hemiptera: Aphididae), is a significant insect pest of soybean, Glycine max (L.) Merrill (Fabales: Fabaceae), and field treatment decisions for this pest are based on average field populations. Previous studies indicated that ground- and drone-based red-edge and near-infrared remote sensing can be used to detect plant stress caused by SBA infestations in soybean. However, it remains to be determined if remote sensing for SBA can be expanded to field or landscape scale using satellite-based platforms. Thus, this research was conducted in three steps to determine the potential of using Sentinel-2 satellite data for the classification of SBA infestations in soybean fields using simulated and actual Sentinel-2 satellite spectral reflectance. In the first step, as a proof of concept, hyperspectral data from cage studies were used to simulate Sentinel-2 bands and vegetation indices (VIs), conducted in nine trials at multiple locations between 2013 and 2021. The effects of SBA from caged plants on simulated data were evaluated with random intercept linear mixed models. The satellite simulation indicated a significant effect of SBA on the spectral reflectance of caged soybean plants (p < 0.05) for four satellite bands (5, 6, 7, and 8A) and five VIs (NDVI, GNDVI, SAVI, OSAVI, and NDRE). In the second step, actual Sentinel-2 spectral reflectance and corresponding aphid counts of commercial soybean fields, collected from 2017 to 2019, were obtained. The relationship between SBA counts and Sentinel-2 spectral reflectance from commercial soybean fields were evaluated with general linear models. A significant effect of SBA was observed for three satellite bands (6, 7, and 8A) and three VIs (NDVI, SAVI, and OSAVI). In the third step, linear support vector machine (LSVM) models for the classification of SBA infestations as above or below a previously determined economic threshold of 250 aphids per plant were developed using simulated Sentinel-2 bands and VIs from the caged plots, and were tested on actual Sentinel-2 data from commercial soybean fields. The best LSVM model for the classification of aphids in soybean reached 91% accuracy, 85.7% sensitivity, and 93.3% specificity. Thus, simulations with caged plots can be used as an indication of the potential of using satellite data for the detection of plant stresses on a larger scale. Furthermore, this study advances decision-making for SBA, and the developed LSVM model can be used to update regional and local monitoring for the management of SBA.

Evaluation of Some Eco-Friendly Biorationals against Aphids, Nasonovia ribisnigri in Lettuce

Six biorationals viz. Beauveria bassiana (20 g/L), Neem oil (5 ml/L), Ginger rhizome extract (5%), Garlic bulb extract (2%), Lantana camara extract (5%) and Tobbaco leaf extract (5%) were evaluated against lettuce aphids, Nasonovia ribisnigri. The study was conducted in Random Block Design with seven treatments having three replications each. In the six months study period, our study reported the highest aphid count reduction in plots treated with Neem oil and B. bassiana with a per cent reduction of 95% and 93.60% respectively.

Biochemical probing of phloem sap defensive traits in Brassica juncea-B. fruticulosa introgression lines following Lipaphis erysimi infestation.

The lack of resistance to Lipaphis erysimi in cultivated Brassicas makes caused this pest highly devastating resulting in significant loss of rapeseed-mustard productivity in India. B. fruticulosa, a wild crucifer is known as an excellent source of resistance to L. erysimi. Therefore, we planned to assess defense associated biochemical alterations and molecular components of B. juncea-B. fruticulosa ILs to mustard aphid. Phenotypic assessment of ILs on the basis of aphid population per plant (APP) categorized genotypes into resistant (7.15-18.50 APP), moderately susceptible (42.29-53.33 APP) and susceptible (70.00-77.07 APP) genotypes. Mustard aphid infested minimally B. fruticulosa (0.80 APP) among tested genotypes. The maximum increase in catalase (CAT) activity was determined in B. fruticulosa and resistant ILs after 48h (2.03 and 1.76-fold, respectively) and one week (2.98 and 1.79-fold, respectively) of mustard aphid infestation. The strong induction of CAT2 transcripts (19.25-fold) and CAT activity (5.88-fold) along with low aphid count in resistant IL, Ad4-64 (13.85 APP) suggested the pivotal role of CAT in resistance to mustard aphid. Guaiacol peroxidase (GPX) was significantly decreased following pest infestation at both infestation stages. The ascorbate content was highest in resistant IL, ADV-6RD (2.14-fold) after one week of aphid infestation. H2O2 content rapidly increased in B. juncea-B. fruticulosa derived lines after 48h of aphid infestation. The negative and significant association between APP and CAT (- 0.56** and - 0.48*, respectively), glutathione (- 0.43* and - 0.40*, respectively), H2O2 (- 0.57** and - 0.43*, respectively) at both 48h and one week infestation stages signified their role in deterring mustard aphid infestation. The positive and significant association between total sugars (0.33* at 7 DPI), reducing sugars (0.33* at 7 DPI), sucrose (0.36** at 48h) and APP indicated that higher the sugars content, higher will be mustard aphid infestation in B. juncea derived ILs. The information being generated and key candidates (CAT2, ascorbate and H2O2) being identified may help in effective deployment of B. fruticulosa resistance in mustard breeding.

If Only You Could Catch Me—Catch Me If You Can: Monitoring Aphids in Protected Cucumber Cultivations by Means of Sticky Traps

Aphids are important pests in many greenhouse and field crops. For plant protection, early detection of relevant species and reliable assessment of population development throughout the season is mandatory to address countermeasures in time. In practice, coloured sticky cards or pan traps are frequently used as monitoring tools, but as well as the flight activity of focal insects, many other factors influence reliable interpretation of trapping data. Since monitoring data have been more and more integrated into automated decision support systems, soundness of insect count data and interpretation of results needs to be reviewed in more detail. Therefore, we investigated the applicability of yellow sticky traps for monitoring of the cotton aphid, Aphis gossypii in greenhouse cucumber crop. In separate greenhouse chambers, we infested cucumber plants with Aphis gossypii and installed several yellow sticky traps. Insects were counted on the plants and sticky traps on a weekly basis and number of insects were correlated. Our results indicate mismatches between trap catches and aphid population density especially early in the season, which most likely is related to immigration of winged aphids into the greenhouse. The following population build-up of the cotton aphid Aphis gossypii on the cucumber plants correlated quite well with counts of alate cotton aphids on the sticky traps. In conclusion, trapping of winged aphids provides valuable information for integrated pest control in the greenhouse. Nevertheless, to avoid wrong interpretation the taxonomic identity of trapped aphids has to be confirmed at all times. Results are further discussed in the context of factors influencing aphid wing development and attraction to yellow sticky traps. Potential strategies to optimize aphid monitoring with coloured sticky traps are proposed.

Earliness and Crop Morphological Traits Modulate Field Pest Infestation in Green Gram.

Breeding has significantly improved drought tolerance in green gram but marked yield losses continue due to damage by insect pests. Important pests of green gram are pod borers, Maruca vitrata (F.), aphids, Aphis gossypii Glover and whiteflies, Trialeurodes vaporariorum (Westwood). Management of these pests has partly been constrained by the limited understanding of crop traits that modulate their infestation. Field experiments were conducted in southeastern Kenya to evaluate a collection of old and new green gram varieties for tolerance to field pests, and to identify traits that confer resistance. The old varieties were KS20 and N26, both released in 1990s whereas the modern counterparts were Biashara, Karembo, and Ndengu-Tosha. Results showed significant differences among the varieties in maturity, leaf area, leaf hair density, leaf moisture content, and pod wall thickness. Earliness significantly reduced pest infestation, whereby KS20 matured early while N26 was late, and the new varieties were intermediate. On average, across the three environments, leaf area (R2 ≥ 0.32) and leaf moisture content (R2 ≥ 0.18) positively correlated with pest infestation while leaf hair density (R2 ≥ 0.30), and pod wall thickness (R2 ≥ 0.54) showed a negative association with pod borer and aphid counts. However, results did not reveal any particular traits that associated with the varieties, which implied that breeding of green gram in Kenya has not selected for tolerance to field pests. Nonetheless, green gram field pest management practices could select for varieties with early maturity, open plant canopy, pubescent leaves, and thicker pod walls.

Efficiency of sticky traps for monitoring aphids in wheat under North-Western Plains and Peninsular zones of India

Aim: To evaluate the efficiency of most effective trap among two types of sticky traps of, i.e., card or tray of two colours (yellow and blue) and their placement height within wheat crop for catching alate of R. maidis, the most abundant aphid species in selected locations. Methodology: Sticky card and tray traps of two colours; yellow and blue were placed at different heights within wheat crop and the effects of trap parameters (type, colour and height) were evaluated to determine the trapping efficiency of R. maidis alate. The traps were installed at two heights above ground level; 100 cm and 150 cm at Karnal and Ludhiana and at 60 cm and 120 cm above ground level at Niphad location. Alate aphid counts were recorded weekly to make comparisons. Results: The highest number of R. maidis alate were caught on yellow coloured sticky card traps placed within the crop canopy at 100 cm height above ground and the lowest on blue coloured sticky tray traps at 150 cm height above ground at Ludhiana and Karnal. At Niphad, the highest population was caught on yellow coloured sticky card traps placed at 60 cm height above ground and the lowest number on blue coloured sticky tray traps at 120 cm height above ground. Correlation analysis revealed that all three trap parameters (trap type, colour and placement height) were correlated with mean alate trap catches. Backward stepwise regression modelling indicated that trap type and placement height had a maximum influence on the R. maidis alate trapping. Interpretation: This study indicated that the yellow sticky card traps were most effective in catching R. maidis alate as compared to other tested traps. Key words: Aphids, Insect sampling, Trapping efficiency, Trap parameters, Triticum aestivum

Evaluation of mustard genotypes [Brassica juncea (L.) Czern and Coss] for quantitative traits and character association of seed yield and yield components at sub Himalayan region of West Bengal (India)

Brassica juncea is an important industrial and commercial oilseed crop grown primarily in India. This study aimed to assess 56 genotypes of Indian mustard to quantify genetic diversity, which aids the breeder in identifying genetically divergent parents to evaluate the proportional contributions of various components towards overall divergence. All the 56 Indian mustard genotypes were tested in RBD with three replications for 2 consecutive years i.e. 2016-17 and 2017-18 during the rabi season. Observations were recorded for 11 yield and its attributing traits. The findings revealed that height up to first branching, aphid count, penetration force and seed yield per plant had maximum PCV and GCV signifying that genetic factors have a greater impact on the inflow of these traits. Height up to first branching, secondary branches per plant, primary branches per plant, siliquae per plant, aphid count and 1000 seed weight had strong heritability combined with GA as % of mean. These indicate that the traits were controlled by additive gene action. Seed yield per plant was significantly correlated with penetration force and siliquae per plant. As a result, it's reasonable to predict that improving these traits by selection, could lead to significant yield gains. Four of the eleven PCs had eigen values greater than 1.0, accounting for 69.94% of the variance. PC I, which explained 30.31% of the overall variance. Mahalanobis D2 statistics revealed considerable genetic diversity among the genotypes. 56 genotypes were distributed into 7 clusters. This is anticipated that genotypes within a cluster are almost genetically related to one another. Cluster VII and II showed maximum inter-cluster divergence. From a breeding perspective, a divergence analysis revealed that genotypes like SKJM-05, RNWR-09-3, RW-351, B-85, DRMR-4001, RGN-386, TM52 276 and SKM-1313 can be selected as genetically divergent parents for hybridization to obtain desirable segregants.

Efficacy of Botanicals Against Mustard Aphid (Lipaphis Erysimi Kalt.) (Homoptera: Aphididae) On Brassica Campestris L.

Efficacy of neem leaf extract, mahogany seed dust, and neem seed kernel dust against the mustard aphid Lipaphis erysimi Kalt., (Homoptera: Aphididae) on the mustard plant (Brassica campestris L.) was investigated during November 2014 to January 2015. The trial included four treatments, namely T1: neem leaf extract, T2: mahogany seed dust, T3: neem seed kernel dust, T4: control. The treatments began 22 DAS and were repeated every 7 days. T4 had the maximum number (9500 ± 1226.3) of aphid pest population at 57 DAS, and the lowest number (3 ± 0.9) of aphid pest population was found in T4 at 29 DAS. The aphid population was found to be nil at 22 and 71 DAS in all treatments. Furthermore, in case of T2, the aphid population was zero at 29 DAS. There was no significant difference in aphid counts between the treatments, according to the ANOVA test. Only in T2, the aphid counts showed a significant difference by replicates. But the number of fruits and seed output of mustard were affected by the efficacy of botanicals against mustard aphid. T1 exhibited the highest percentage of fruits (27.7%), seeds (42.64%), and seed weight (54.9%). T1 had the highest proportion of healthy seed (75.91%), whereas T4 had the highest percentage of defective seed (45.49%). Aphid population is negatively correlated to average temperature and relative humidity in all treatments. Bangladesh J. Bot. 51(3): 615-623, 2022 (September)

Host plant resistance, foliar insecticide application and natural enemies play a role in the management of Melanaphis sorghi (Hemiptera: Aphididae) in grain sorghum.

The invasive Melanaphis sorghi (Theobald; =Melanaphis sacchari Zehntner) is a serious pest of sorghum production in the southern USA. Demonstration of technologies that provide effective control is key to management of this pest. Here, we investigated the effect of host plant resistance (resistant cultivar: DKS37-07 and susceptible cultivar: DKS53-53) and a single foliar insecticide (flupyradifurone: Sivanto Prime) application on M. sorghi infestations and the role of natural enemy populations in grain sorghum production across five locations in four states in southeastern USA. Foliar insecticide application significantly suppressed M. sorghi infestations on both the resistant and susceptible sorghum cultivars across all locations. Planting the host plant resistant cultivar (DKS37-07) significantly reduced aphid infestation across all locations. Plant damage ratings did not vary widely, but there was generally a positive association between aphid counts and observed plant damage, suggesting that increasing aphid numbers resulted in corresponding increase in plant damage. Planting a host plant resistant cultivar and foliar insecticide application generally preserved grain yield. Both sorghum hybrids supported an array of different life stages of natural enemies (predators [lady beetle larvae and adults; hoverfly larvae and lacewing larvae] and parasitoids [a braconid and aphelinid]) for both the sprayed and non-sprayed treatments. We found a strong and significant positive relationship between the natural enemies and the M. sorghi infestation. Results suggest that planting a host plant resistant cultivar and the integration of natural enemies with insecticide control methods in the management of M. sorghi is central to the development of an effective pest management strategy against this invasive pest.

Genome-wide association mapping of resistance to the sorghum aphid in Sorghum bicolor

Since 2013, the sorghum aphid (SA), Melanaphis sorghi (Theobald), has been a serious pest that hampers all types of sorghum production in the U.S. Known sorghum aphid resistance in sorghum is limited to a few genetic regions on SBI-06. In this study, a subset of the Sorghum Association Panel (SAP) was used along with some additional lines to identify genomic regions that confer sorghum aphid resistance. SAP lines were grown in the field and visually evaluated for SA resistance during the growing seasons of 2019 and 2020 in Tifton, GA. In 2020, the SAP accessions were also evaluated for SA resistance in the field using drone-based high throughput phenotyping (HTP). Flowering time was recorded in the field to confirm that our methods were sufficient for identifying known quantitative trait loci (QTL). This study combined phenotypic data from field-based visual ratings and reflectance data to identify genome-wide associated (GWAS) marker-trait associations (MTA) using genotyping-by-sequencing (GBS) data. Several MTAs were identified for SA-related traits across the genome, with a few common markers that were consistently identified on SBI-08 and SBI-10 for aphid count and plant damage, as well as loci for reflectance-based traits on SBI-02, SBI-03, and SBI-05. Candidate genes encoding leucine-rich repeats (LRR), Avr proteins, lipoxygenases (LOXs), calmodulins (CAM) dependent protein kinase, WRKY transcription factors, flavonoid biosynthesis genes, and 12-oxo-phytodienoic acid reductase were identified near SNPs that had significant associations with different SA traits. In this study, flowering time-related genes were also identified as a positive control for the methods. The total phenotypic variation explained by significant SNPs across SA-scored traits, reflectance data, and flowering time ranged from 6 to 61%, while the heritability value ranged from 4 to 69%. This study identified three new sources of resistant lines to sorghum aphid. These results supported the existing literature, and also revealed several new loci. Markers identified in this study will support marker-assisted breeding for sorghum aphid resistance.

Suppression of the Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), by Resident Natural Enemies on Susceptible and Resistant Sorghum Hybrids.

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive sorghum pest that has threatened over 90% of North American sorghum production. Resident parasitoids, coccinellids, syrphids, and lacewings prey on this aphid. Our objective was to compare and estimate parasitoid and predator suppression of sugarcane aphids placed on resistant and susceptible hybrids in a field setting using natural enemy exclusion cages. During 2018 and 2019 along the Texas Gulf Coast and Central Oklahoma, three natural enemy exclusion treatments-no exclusion (full access for parasitoids and predators), partial exclusion (access limited to parasitoids), and complete exclusion (excludes parasitoids and predators)-were used. The parasitoid Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) accounted for 90% of recovered natural enemies. In 2018, aphid suppression attributable to A. nigritus was ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from complete and partial exclusion treatments, while few predators were observed. In 2019, aphid suppression was attributed to a combination of predation and parasitism. Relatively more predators were recorded at both sites, accounting for 14% to 33% of specimens recovered in the no exclusion treatment. Aphid suppression attributed to predators and parasitoids ranged from 85% on aphid-resistant hybrids and 27% on susceptible hybrids in south Texas and >95% on both hybrids in Oklahoma when comparing aphid abundance in the complete and no exclusion treatments. Parasitism and predation contributed to aphid regulation on both hybrids, which may accrue multiple benefits leading to a more resilient sugarcane aphid management system.

Recruitment of Natural Enemies of the Invasive Sugarcane Aphid Vary Spatially and Temporally in Sorghum Fields in the Southern Great Plains of the USA

Sorghum (Sorghum bicolor (L.) Moench) is an important summer grain crop in the U.S. Southern Great Plains because it is one of the few crops that consistently produces acceptable yields in the harsh summer weather that characterizes the region. Damaging infestations of the sugarcane aphid, Melanaphis sacchari (Zehntner), occur commonly in sorghum throughout Texas and Oklahoma, two of the leading sorghum producing states. Grain sorghum fields were sampled at two locations in Texas and three locations in Oklahoma. Fields were sampled approximately weekly by examining two leaves on each of 54 plants and counting all sugarcane aphids and aphid natural enemies on each leaf. Sampling began at an early growth stage and continued until the crop either matured or was treated with insecticide to suppress the sugarcane aphid infestation. For a total of 123 fields in 2017 and 2018, aphids, Aphelinus nigritus Howard mummies, adult coccinellids, larval coccinellids, larval lacewings, and larval dipterans were counted, and relative density estimates were determined. When natural enemy and sugarcane aphid count data were aggregated at the scale of geographic locations and multiple years, there was no evidence for a numerical response by natural enemies to sugarcane aphid density. When fields were compared within locations, a numerical response was consistently observed. A natural enemy importance index was developed that incorporated cumulative degree days of first occurrence of a natural enemy taxa in a field, the average density of the natural enemy in a field, and natural enemy voracity. Factorial analyses of variance indicated that cumulative degree days at first occurrence and average relative density differed significantly among natural enemy taxa and locations, as did natural enemy importance. Averaged across locations larval coccinellids had the largest importance index, I = 1.47, and A. nigritus had the smallest, I = 0.61. Among locations, the Texas Coastal Plains had the largest importance index, I = 1.27 whereas the Oklahoma Panhandle had the smallest, I = 1.02. Results suggest that differences occur in the biological control contributions of various natural enemies and in biological control efficacy among locations.

Tally-based thresholds as an alternative to density-based thresholds for sugarcane aphid, Melanaphis sacchari, (Hemiptera: Aphididae) in grain sorghum

Sugarcane aphid, Melanaphis sacchari Zehtner (Hemiptera: Aphididiae), has become a major pest of grain sorghum, Sorghum bicolor (L.) Moench, in North America since being detected in 2013. A density-based economic threshold of 40 aphids per leaf has been established for hybrids susceptible to the aphid. Direct counts of aphids are needed for use of density-based thresholds, but the counts are time-consuming and may rely on estimation of numbers of aphids in clusters which may vary in accuracy. Therefore, a tally-based threshold was considered by evaluating the aphid infestation proportion – aphid density relationship for three selected tallies, validating the tally-based approach in decision-making, and comparing time efficiency of the two approaches. Using data collected at three Texas locations from 2015 to 2018, linear and polynomial regressions for tallies of >25, >50, and >100 aphids per leaf were related to aphid densities, with polynomial regressions providing the best fit. Solving the equations, tally threshold proportions of 0.23, 0.16, and 0.11 using a tally of >25, >50, and >100 aphids per leaf, respectively, were equivalent to a density-based threshold of 40 aphids per leaf. In a validation exercise using 50 and 100 aphids per leaf tally thresholds and a fixed sample size of 100 leaves from five commercial grain sorghum fields of varying aphid density, the tally threshold infestation proportion derived from the polynomial regressions produced the same management decision in all cases. Additionally, the tally-based threshold approach was more time efficient than the density-based approach, requiring half the time to sample 100 leaves.

Tree Diversity and Damage by Cypress Aphid, Cinara cupressi, on Juniperus procera in Gulele Botanical Garden and Entoto

Juniperus procera is an important tree species in Ethiopia. Increasing demand for fuelwood and construction material has also created markets for J. procera products. The impact of cypress aphid, Cinara cupressi, on J. procera is becoming catastrophic in the country. However, the level of cypress aphid damage on J. procera has never been studied in Entoto Mountain forest and Gullele Botanical Garden (GBG) in Ethiopia. The objective of this study was to assess the cypress aphid densities and extent of damage caused by the cypress aphid on solely and mixed planted J. procera in Entoto Mountain forest and GBG in Addis Ababa, Ethiopia, by evaluating aphid adult and nymph densities and damage to J. procera trees. Eight plots of 50 m ∗ 50 m planted with pure J. procera and mixed J. procerawere selected at each site. Five 5 m ∗ 5 m subplots were formed. To assess aphid density hthree tree twigs per whorl were sampled from each tree in the subplots randomly. The collected samples were examined in the laboratory for the presence of nymph and adult cypress aphid. Tree damage was assessed by visually observing the percentage of infestation in the tree crown and was scored on a 1–5 scale. The results showed significant differences in aphid densities between the sites. The highest aphid count was observed at Entoto Mountain. Besides, the solely planted J. procera trees had higher cypress aphid numbers than the mixed plantation. The mean percentage of aphid-infested trees in Entoto and GBG was 53.6 and 46.4, respectively. Tree mortality was extremely low in both sites and planting systems. The level of aphid damage was also significantly different between the planting systems, where mixed plantations had a lower aphid infestation level. Tree damage was directly correlated with the density of aphids collected. In conclusion, cypress aphid was apparent in both sites, and most of the trees were infested by this pest. However, the extent of damage varied with the planting system. Therefore, it is recommended to consider a mixed plantation of trees as one of cypress aphid management tools in J. procera.

191 Yield and nutritive quality of summer annual forage mixtures

Abstract Summer annual forage mixtures are both high yielding and contain a high nutritive quality. They provide a summer forage option for maintaining stockers, forage-finished beef, and replacement heifers on with little to no external inputs needed. Recently, sugarcane aphid infestations have limited production of sorghum × sudangrass (Sorghum bicolor var. bicolor*bicolor var. sudanese; S). This study investigated mono-, bi-, and tri- cultures of S, cowpea (Vigna unguiculata; C), and crabgrass (Digitaria ciliaris; R). Forage yield, CP, NDF, ADF, ADL, and sugarcane aphid counts were determined for each treatment. Sugarcane aphid counts were conducted on a weekly basis during the study and forage samples were harvested twice during each season. A forage subsample was taken for determination of CP, NDF, ADF, and ADL using wet chemistry. Data were analyzed using Proc Glimmix of SAS 9.4 (SAS inst., Cary, NC). During Year 1, the only difference in yield among treatments was observed in R, which was lower than other plots (949 and 1,259 kg/ha, respectively; P &amp;lt; 0.05). Neutral detergent fiber was greatest (P &amp;lt; 0.0001) in treatments containing S, whereas C and C+R had the least NDF (64.6%, 55.1%, and 56.6%, respectively; P &amp;lt; 0.02). Sugarcane aphids were greater (P &amp;lt; 0.0001) in S+C compared to S+R and SI on July 12 (33.5, 21.1, and 22.4 aphid days/ two leaf sample, respectively). During Year 2, there were no differences in yield among plots (996 kg/ ha, P &amp;gt; 0.9); NDF was greatest in S and lowest in plots containing C and C+R (63%, 46%, and 45.6%, P &amp;lt; 0.0001). While there appeared to be no reduction in sugarcane aphid pressure in the mono- and mixed- cultures of S, C+R showed promise as a summer annual mixture with similar yield and higher quality to that of S and S mixtures.