Sugarcane Aphid Populations Research Articles

Melanaphis sacchari/sorghi complex: current status, challenges and integrated strategies for managing the invasive sap-feeding insect pest of sorghum.

Melanaphis sacchari (Zehntner;Hemiptera: Aphididae), sugarcane aphid (SCA), is an invasive phloem-feeder found worldwide with a wide host range of economically important plants including sorghum and sugarcane. Given its high reproductive capacity and ability to rapidly spread over long distances, SCA presents challenges for effective control, leading to substantial economic losses. Recent studies have identified two multiloci SCA genotypes specialized in feeding on sugarcane (MLL-D) and sorghum (MLL-F) in the USA, which raises concerns as the USA is the second largest sorghum-producing country. This has encouraged research towards identifying these two biotypes where some research has stated them as two species; MLL-D clade to be M. sacchari and MLL-F clade to be M. sorghi Theobald (Hemiptera: Aphididae), sorghum aphid (SA). This review aims at compiling research progress that has been made on understanding the SCA/SA species complex. Furthermore, this review also highlights a wide range of management strategies against SCA/SA that includes both biological and chemical methods. In addition, the review emphasizes studies examining host plant resistance to understand and evaluate the role of R-genes and phytohormones such as jasmonic acid, salicylic acid and ethylene against SCA. Beside this, plant volatiles and other secondary metabolites such as flavonoids, terpenes and phytanes are also explored as potential control agents. Being an invasive pest, a single management tactic is inadequate to control SCA population and hence, integrated pest management practices incorporating physical, cultural and biological control methods should be implemented with exclusive chemical control as a last resort, which this review examines in detail. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Detecting common coccinellids found in sorghum using deep learning models

Increased global production of sorghum has the potential to meet many of the demands of a growing human population. Developing automation technologies for field scouting is crucial for long-term and low-cost production. Since 2013, sugarcane aphid (SCA) Melanaphis sacchari (Zehntner) has become an important economic pest causing significant yield loss across the sorghum production region in the United States. Adequate management of SCA depends on costly field scouting to determine pest presence and economic threshold levels to spray insecticides. However, with the impact of insecticides on natural enemies, there is an urgent need to develop automated-detection technologies for their conservation. Natural enemies play a crucial role in the management of SCA populations. These insects, primary coccinellids, prey on SCA and help to reduce unnecessary insecticide applications. Although these insects help regulate SCA populations, the detection and classification of these insects is time-consuming and inefficient in lower value crops like sorghum during field scouting. Advanced deep learning software provides a means to perform laborious automatic agricultural tasks, including detection and classification of insects. However, deep learning models for coccinellids in sorghum have not been developed. Therefore, our objective was to develop and train machine learning models to detect coccinellids commonly found in sorghum and classify them according to their genera, species, and subfamily level. We trained a two-stage object detection model, specifically, Faster Region-based Convolutional Neural Network (Faster R-CNN) with the Feature Pyramid Network (FPN) and also one-stage detection models in the YOLO (You Only Look Once) family (YOLOv5 and YOLOv7) to detect and classify seven coccinellids commonly found in sorghum (i.e., Coccinella septempunctata, Coleomegilla maculata, Cycloneda sanguinea, Harmonia axyridis, Hippodamia convergens, Olla v-nigrum, Scymninae). We used images extracted from the iNaturalist project to perform training and evaluation of the Faster R-CNN-FPN and YOLOv5 and YOLOv7 models. iNaturalist is an imagery web server used to publish citizen’s observations of images pertaining to living organisms. Experimental evaluation using standard object detection metrics, such as average precision (AP), AP@0.50, etc., has shown that the YOLOv7 model performs the best on the coccinellid images with an AP@0.50 as high as 97.3, and AP as high as 74.6. Our research contributes automated deep learning software to the area of integrated pest management, making it easier to detect natural enemies in sorghum.

Response of sugarcane aphid (Melanaphis sacchari) to interactive effects of soil drenched triterpenoid phytonematicides in sweet sorghum (Sorghum bicolor)

Triterpenoid phytonematicides, namely, Nemarioc-AL, Nemafric-BL and Mordica, when drench-applied each consistently suppressed root-knot nematode population densities, with limited information on whether the products could induce any systemic effects that would suppress sugarcane aphid population densities and reproductive potential. The objective of the study was therefore to determine the interactive effects of soil-drenched triterpenoid phytonematicides on aphid population densities and their reproductive factors. A 2× 2× 2 factorial experiment was laid out in a randomised complete block design with six replications during 2020-21 and 2021-22 growing seasons in Limpopo Province, South Africa. Each sweet sorghum seedling was infested with 5 adult M. sacchari, with appropriate treatment combinations drench-applied weekly. At 150 days after infestation, treatments had highly significant effects on aphid population densities and reproductive factors. Relative to untreated control, the second order interaction and the three first order interactions reduced aphid population densities by 92, 75, 79 and 80%, respectively. In conclusion, soil-drenched triterpenoid phytonematicides induced systemic effects in sweet sorghum, which significantly suppressed population densities of M. sacchari.

Dichotomous Role of Jasmonic Acid in Modulating Sorghum Defense Against Aphids.

The precursors and derivatives of jasmonic acid (JA) contribute to plant protective immunity to insect attack. However, the role of JA in sorghum (Sorghum bicolor) defense against sugarcane aphid (SCA) (Melanaphis sacchari), which is considered a major threat to sorghum production, remains elusive. Sorghum SC265, previously identified as a SCA-resistant genotype among the sorghum nested association mapping founder lines, transiently increased JA at early stages of aphid feeding and deterred aphid settling. Monitoring of aphid feeding behavior using electropenetrography, a technique to unveil feeding process of piercing-sucking insects, revealed that SC265 plants restricted SCA feeding from the phloem sap. However, exogenous application of JA attenuated the resistant phenotype and promoted improved aphid feeding and colonization on SC265 plants. This was further confirmed with sorghum JA-deficient plants, in which JA deficiency promoted aphid settling, however, it also reduced aphid feeding from the phloem sap and curtailed SCA population. Exogenous application of JA caused enhanced feeding and aphid proliferation on JA-deficient plants, suggesting that JA promotes aphid growth and development. SCA feeding on JA-deficient plants altered the sugar metabolism and enhanced the levels of fructose and trehalose compared with wild-type plants. Furthermore, aphid artificial diet containing fructose and trehalose curtailed aphid growth and reproduction. Our findings underscore a previously unknown dichotomous role of JA, which may have opposing effects by deterring aphid settling during the early stage and enhancing aphid proliferative capacity during later stages of aphid colonization on sorghum plants. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Field Assessment of Aphid Doubling Time and Yield of Sorghum Susceptible and Partially Resistant to Sugarcane Aphid (Hemiptera: Aphididae).

Since outbreaks were first detected in grain sorghum, Sorghum bicolor (L.) Moench (Cyperales: Poaceae), in 2013, sugarcane aphid, Melanaphis sacchari Zehntner has become a major annual pest in grain sorghum-producing regions of North America. Economic thresholds have been recommended for susceptible hybrids, but these recommendations may not be suitable for grain sorghum hybrids partially resistant to sugarcane aphid. The objectives were to evaluate the grain yield-aphid density relationship and field-based population growth rates of the aphid on sorghum hybrids susceptible and partially resistant to sugarcane aphid across multiple years, locations, and hybrids. These data verified previously established economic injury levels for susceptible hybrids. The observed maximum aphid density ranged from 6 to 451 aphids per leaf for resistant hybrids and from 67 to 1,025 for susceptible hybrids. Across 50 location-year combinations, the maximum aphid density observed on resistant hybrids decreased by 0-99%, compared to a susceptible hybrid at the same location (mean reduction = 80%). Doubling time for sugarcane aphid populations on partially resistant hybrids was up to 6.4-fold higher than on known susceptible hybrids. For 48 of the 50 location-years, yield loss attributable to sugarcane aphid was not detected on the partially resistant hybrids; therefore, an economic injury level was unable to be estimated. If an economic injury level exists for resistant hybrids, it is likely at an aphid population level that exceeds the levels experienced in this study. It remains prudent to monitor resistant hybrids for unusual leaf decay associated with aphid densities that exceed current economic injury levels used for susceptible hybrids.

Assessing spatio-temporal patterns of sugarcane aphid (Hemiptera: Aphididae) infestations on silage sorghum yield using unmanned aerial systems (UAS)

In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum. Rating sugarcane aphid population density, plant damage, and other traits in sorghum requires a large amount of labor and ratings, especially damage ratings, may vary by evaluator. Thus Unmanned Aerial Systems (UAS)–based imagery may be exceedingly useful to more accurately quantify the effects on sorghum caused by sugarcane aphids. This study quantified the dynamic nature of sugarcane aphid infestations on silage sorghum varieties using UAS-based imagery data, and demonstrated the UAS-based measurements correlated to ground measurements. Two UAS platforms equipped with RGB (red, green, and blue) and multispectral cameras respectively were used to evaluate the silage sorghum variety trials during the growing seasons of 2019 and 2020. For the purpose of high throughput phenotyping in sorghum breeding, a new workflow scheme was developed including UAS image processing, raster calculation, DTM (digital terrain model) and CHM (canopy height model) generation, image extraction of sorghum plants, and tabular dataset generation from zonal statistics for further statistical analyses. Ground-based measurements included aphid sampling, aphid damage ratings, plant height, and biomass yields. The normalized difference red edge index (NDRE) and canopy cover collected by the UAS showed negative linear relationship with aphid damage ratings in both trials (R2 = 0.55–0.64). In addition to assessing spatial differences among the varieties in 2019, temporal change in both NDRE and canopy cover from the baseline sampling date in 2020 better estimated aphid damage, R2 of 0.68 and 0.79 respectively, than using the spatial difference of NDRE (R2 = 0.55) and canopy cover (R2 = 0.57) before harvest. Plant height (R2 = 0.84, Root-Mean-Square Error (RMSE) = 0.16 m) can be estimated with efficiency and precision using UAS-derived measurements during high throughput phenotyping of sorghum. Fresh yield estimates for the primary harvests were consistent in both years, but green yield estimates differed among harvests and need to be improved. Future development of UAS-based high throughput phenotyping would benefit from increased temporal resolutions of growth parameters and vegetation indices throughout a growing season.

Evaluating Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), Population Dynamics, Feeding Injury, and Grain Yield Among Commercial Sorghum Varieties in Alabama.

The sugarcane aphid, Melanaphis sacchari (Zehntner), emerged as a severe pest of sorghum, Sorghum bicolor (L.), in Texas and Louisiana in 2013 and currently threatens nearly all sorghum production in the United States. Proper management of populations is critical as sugarcane aphid has a high reproductive potential and can rapidly damage plants, resulting in extensive yield losses. The overall objective of this work was to investigate sugarcane aphid population dynamics, and subsequent sorghum injury and grain yield on commercially available grain sorghum varieties in Alabama. This research includes three-site years of data that show variation in plant injury, physiological maturity, and yields among varieties tested. Although performance of each variety was variable among locations, potentially due to abiotic factors, four varieties including DKS 37-07, 1G588, 1G855, and 83P17 exhibited characteristics consistent with resistance and corroborates reports of resistance from other states.

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.

Sugarcane aphids in grain sorghum

AbstractSugarcane aphids made their way into the southern US in 2013, and have since been spreading throughout the country. They are asexually reproducing Hemipterans, each capable of producing up to 60 young. Like other Hemipterans, sugarcane aphids use piercing‐sucking mouthparts to feed on plant sap. This feeding causes chlorosis and necrosis in sorghum, and the severity of damage depends on crop stage. Sugarcane aphids also excrete sticky honeydew, inviting sooty mold infections and causing problems during harvest. Management of this insect begins by scouting for economically damaging populations. If an economic injury level is reached, there are insecticides available on the market for control. Biological control is also an option, but can be difficult to maintain. To prevent high levels of damage, a tolerant hybrid can be planted. Sugarcane aphid populations have the ability to explode due to the insect's biology; scouting is necessary to decide when management is necessary.

Identification of Predatory and Parasitoid Insect Species Associated with Melanaphis sacchari (Hemiptera: Aphididae), a Sorghum Pest in Nuevo León, Mexico

Melanaphis sacchari Zehntner (Hemiptera: Aphididae) is an important destructive pest in forage sorghum in Nuevo Leon, Mexico. This study was conducted to identify predatory and parasitoid insect species associated with this pest in Nuevo Leon, and their impact on its biocontrol. During the monitoring period, identified insects indicated the coexistence of 8 coccinellid species, 2 syrphid species, and 1 chrysopid species. In addition, 2 hymenopteran species were identified. After the insecticide applications, sugarcane aphid population was reduced by about 20.6% (about 14 nymphs per cm2); when the sampling ended, population was reduced by about 70.6% (about 5 nymphs per cm2), thus indicating predator and parasitoid biocontrol. Collected data allowed us to conclude that the biological controllers were responsible for the principal pest population reduction. Overall, results showed that yellow sugarcane aphid predatory and parasitoid species may play an important role in the pest management in sorghum crops in Nuevo Leon, Mexico.

Assessment of Consensus-Based Scouting for Management of Sugarcane Aphid (Heteroptera: Aphididae) in Georgia

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Heteroptera: Aphididae), was recently recognized as a pest of grain sorghum, Sorghum bicolor (L.) Moench, in the southeastern United States. The objectives of the study reported herein were to evaluate the suitability of using a consensus-based scouting network and determine the timing of insecticide applications for management of sugarcane aphid in grain sorghum. The timing of insecticide applications was (1) application at 25 aphids per leaf, (2) application at 50 aphids per leaf, (3) a delayed application 1 week after occurrence of 50 aphids per leaf, or (4) not treated. Results showed that a single application of flupyradifurone at 15.4 g(AI)/ha consistently reduced populations to nearly zero for the remainder of the season, while aphid populations in the nontreated plots reached a peak of 300–400 aphids per leaf. Aphid populations on the upper leaves reached 50 aphids per leaf in nontreated plots 1 week after reaching the treatment threshold on the lower leaves. All plots receiving insecticide applications had similar estimated yields, which were >5 times greater than yields in nontreated plots. Results from the consensus-based scouting network showed that first detections and reported first commercial applications generally occurred within 1 week (range of 3–11 d) of the actual populations quantified in the research trials. These data suggest that initiating scouting for sugarcane aphid populations following notification of activity in the area through consensus reporting would provide adequate warning for preventing economic losses to sugarcane aphid.

Impact of Planting Date on Melanaphis sacchari (Hemiptera: Aphididae) Population Dynamics and Grain Sorghum Yield.

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), has become a major pest of grain sorghum, Sorghum bicolor (L.) Moench, in the United States in recent years. Feeding by large densities of sugarcane aphids causes severe damage, which can lead to a total loss of yield in extreme cases. Our objective was to determine the effect of grain sorghum planting date on sugarcane aphid population dynamics and their potential to reduce yields. We conducted field experiments from 2015 to 2017 in which an aphid-susceptible grain sorghum hybrid was planted at four different dates, which encompassed the typical range of planting dates used in Arkansas production systems. Plots were either protected from sugarcane aphid feeding using foliar insecticide sprays, or left untreated to allow natural populations of sugarcane aphids to colonize and reproduce freely. Planting date impacted both the magnitude and severity of sugarcane aphid infestations, with the highest population densities (and subsequent reductions in sorghum yield) generally occurring on plots that were planted in May or June. Sugarcane aphid feeding reduced yields in the untreated plots in two of the four planting date categories we tested. Earlier planting generally resulted in less sugarcane aphid damage and improved yields compared with later planting dates. While the effect of planting date on sugarcane aphid populations is likely to vary by region, sorghum producers should consider grain sorghum planting date as a potential cultural tactic to reduce the impact of sugarcane aphid.

Development of Economic Thresholds for Sugarcane Aphid (Hemiptera: Aphididae) in Susceptible Grain Sorghum Hybrids.

Sugarcane aphid, Melanaphis sacchari Zehtner (Hemiptera: Aphididae), outbreaks on grain sorghum were first detected in the United States in 2013. The spread of sugarcane aphid across the sorghum-producing regions of North America necessitated increased insecticide use to mitigate economic loss. A field experiment to develop economic thresholds for sugarcane aphid was conducted 15 times across seven locations across the southern United States during 3 yr (2014-2016). Grain sorghum hybrids were evaluated by measuring yield in response to a range of aphid infestations. Yield-aphid population density relationships were described by linear function, which facilitated calculating economic injury levels and economic thresholds. The slopes of the yield-aphid density regressions were significant, negative, and relatively stable across locations, years, and agronomic conditions. The relationships aggregated into two groups, populations that exhibited relatively slow and fast population growth, and common economic injury levels were determined using control costs and market values of grain. Average economic injury levels of 37 and 102 aphids per leaf were most applicable to the two groupings of sorghum/aphid relationships and aphid population growth. Using field-based sugarcane aphid population doubling time estimated from weekly observations of aphid densities, economic thresholds were calculated, ranging from 19 to 132 aphids per leaf across the 15 locations-years. Without site-specific knowledge of a slow-growing aphid population and given cost and market price variability of the system, a 40 aphid per leaf threshold is most prudent to use across the range of hybrid, environmental, and market conditions experienced in this study.

Species Diversity of Entomopathogenic Fungi Infecting the Sugarcane Aphid <i>Melanaphis sacchari</i>: A Recently Introduced Pest in Mexico

The sugarcane aphid, Melanaphis sacchari, is a key pest that affects sorghum in Mexico. During 2014 to 2016, in South of Tamaulipas sites and Bajio region in Guanajuato, the populations of this aphid were infected by different species of Hypocrealean fungi. Based in the morphometric identification and molecular characterization, the species associated with sugarcane aphid in South of Tamaulipas were Lecanicillium longisporum, Beauveria bassiana and Isaria javanica. In this region, the higher infection levels were caused by L. longisporum, mortality range from 30.0% to 50.0%. The presence of I. javanica and B. bassiana represented less than 26.0% and 10.0%, respectively. In Guanajuato, the species found corresponded to L. longisporum and B. bassiana. The infection levels of both species in sugarcane aphid populations in Guanajuato sites were less than 1.00%. The natural occurrence of entomopathogenic fungi on sugarcane aphid populations was associated with climactic factors such as temperature and relative humidity and development of infections was possibly affected by abiotic factors such as crop phenological stage and applications of chemical insecticides realized by farmers for control of this aphid. Further studies on the ecology and physiology of these fungi and trials to determine virulence and persistence in M. sacchari populations are needed. This is the first report on natural presence of L. longisporum, B. bassiana and I. javanica causing disease on Melanaphis sacchari in Guanajuato and Tamaulipas, Mexico.

The effects of sugarcane aphid density in sorghum on predation by lady beetles and lacewings

The sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae), is a new and devastating pest of sorghum (Sorghum bicolor (L.)) in the United States. Arthropod predators, especially lady beetles and green lacewings, are often abundant in sugarcane aphid-infested sorghum, but little is known about the effects of these predators on sugarcane aphid populations. We quantified the effect of two species of lady beetles (larvae and adults of Coccinella septempunctata L. and Harmonia axyridis Pallas) (Coleoptera: Coccinellidae) and green lacewings (larvae of Chrysoperla rufilabris Burmeister) (Neuroptera: Chrysopidae) on aphid colony growth across several aphid densities (20, 40, 80, 160). We found that all predator species and life stages significantly reduced the growth of sugarcane aphid populations at low to intermediate aphid densities (20, 40, and 80 aphids per colony). At the highest aphid density (160 aphids), however, H. axyridis larvae were much less effective than C. septempunctata larvae and adults and H. axyridis adults and lacewing larvae did not suppress sugarcane aphid colony growth. We incorporated these predator effects into a dynamic predator-prey model to predict the impact of predators on the short-term population dynamics of sugarcane aphids in sorghum (2–14 days) and the ability of these predators to suppress aphids below action thresholds (50–75 aphids per leaf). The model illustrated that all the predators we studied prevented aphid densities between 20 and 40 per leaf from reaching action thresholds. At initial densities of 80 aphids per colony, all predators were able to suppress aphids below threshold in two to four days. At the highest initial aphid density (160), however, H. axyridis larvae could not suppress aphids below the action threshold by four days and lacewing larvae never suppressed aphids below the threshold. Our results suggest that common predators in sorghum have the potential to suppress sugarcane aphid population growth and reduce the number of insecticide applications needed to control sugarcane aphids.

Spontaneously Aborted Embryos in the Sugarcane Aphid (Hemiptera: Aphididae)

A spontaneously abortive embryo (SAE) process in field and greenhouse populations of sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae) is described, as well as the occurrence of SAE in populations from Chiapas, Durango, Guanajuato, Nayarit, Michoacan, Queretaro, Sinaloa, and San Luis Potosi states in Mexico. This phenomenon was observed from November 2014 to December 2017 in sugarcane aphid populations grown on Sorghum bicolor (sorghum), Sorghum drummondi (Sudan grass), and Sorghum halepense (Johnson grass). No reports of this phenomenon have been recorded earlier, perhaps due to the small size of the aborted embryos (200–500 μm), the dark color they acquire within few hours of exposure, their frequent drop from the plant, and the crowded populations of aphids. The abortion process, both simple as well as multiple and complex events, are described. Also, embryos in vivo, alcohol-fixed, and mounted individuals are described. Embryogenic stages 13 and 16–19 were identified in the aborted embryos. It is suggested that specific biotic and/or abiotic situations may intervene on the reproductive physiology of these particular populations, most probably, on the hormone balance. However, the presence of a complex symbiotic/pathogenic microbial association is not discarded, according to some observations, which are still to be studied.

Invasion of sorghum in the Americas by a new sugarcane aphid (Melanaphis sacchari) superclone.

In the United States (US), the sugarcane aphid (SCA) Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae) was introduced in the 1970s, however at that time it was only considered a pest of sugarcane. In 2013, a massive outbreak of M. sacchari occured on sorghum, resulting in significant economic damage to sorghum grown in North America including the US, Mexico, and Puerto Rico. The aim of the present study was to determine if the SCA pest emergence in American sorghum resulted from the introduction of new genotypes. To this end we used microsatellite markers and COI sequencing to compare the genetic diversity of SCA populations collected in the Americas after the 2013 SCA outbreak on sorghum (during 2013–2017) to older samples collected before the pest outbreak (during 2007–2009). Our results show that the SCA outbreak in the Americas and the Caribbean observed since 2013 belong to populations exhibiting low genetic diversity and consisting of a dominant clonal lineage, MLL-F, which colonizes Sorghum spp. and sugarcane. The comparison of MLL-F specimens collected post-2013 with specimens collected in Louisiana in 2007 revealed that both populations are genetically distinct, according to COI sequencing and microsatellite data analyses. Our result suggest that MLL-F is a new invasive genotype introduced into the Americas that has spread rapidly across sorghum growing regions in the US, Mexico, Honduras and the Caribbean. The origin of this introduction is either Africa or Asia, with Asia being the most probable source.

Interactive effects of crop variety, insecticide seed treatment, and planting date on population dynamics of sugarcane aphid (Melanaphis sacchari) and their predators in late-colonized sorghum

Sugarcane aphids Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae) have recently become an eruptive and costly pest of sorghum, Sorghum bicolor (L). In contrast to its southern range in the United States, sugarcane aphid colonizes sorghum at flowering or just post-bloom in the central High Plains. Thus the goal of this work was to quantify how sorghum resistance (commercially available hybrid DKS37-07), timing of planting (early or conventional plant date), and insecticide seed treatment (clothianidin) affected population dynamics of sugarcane aphids in late-colonized sorghum in the central High Plains. The impacts of these factors on sugarcane aphid densities were measured over two growing seasons, and the numbers of natural enemies of the aphids were quantified as well. Host plant resistance emerged as the main driver of sugarcane aphid population dynamics while planting date and seed treatment had a variable impact on M. sacchari and their predators. Host plant resistance also affected predators of sugarcane aphids and, while not directly explored in this study, potentially altered predator-aphid interactions as well. Diverse natural enemies including Coccinellidae, Syrphidae, Chrysophidae, and Anthocoridae were readily recruited by sugarcane aphid infestations, and predators were strongly correlated with populations of M. sacchari regardless of the seed treatment application or sorghum variety and across planting dates. This research demonstrates that a commercially available resistant sorghum variety provides the most robust protection against this pest in the central High Plains. Further, an already present assemblage of aphid predators recruits readily to aphid-infested sorghum and is likely to provide important biological control services particularly in resistant sorghum.

Sugarcane Aphid Population Growth, Plant Injury, and Natural Enemies on Selected Grain Sorghum Hybrids in Texas and Louisiana.

In response to the 2013 outbreak of sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), on sorghum, Sorghum bicolor (L.), in North America, experiments were conducted at three southern U.S. grain sorghum production locations (Corpus Christi, TX; Winnsboro, LA; Rosenberg, TX). The objectives were to authenticate yield decline on susceptible hybrids (2014 and 2015) and to measure aphid population growth and natural enemy prevalence on susceptible and resistant hybrids with similar genetic background (2014). Yield decline on susceptible hybrids (Tx 2752/Tx430 and DKS53-67) was more substantial when aphid population growth accelerated quickly and peaked above 300 aphids per leaf (50 to nearly 100% yield decline). Location and year variation in maximum aphid density and cumulative aphid-days was high, with doubling time values on the susceptible hybrids ranging between 3.9 and 7.9 d. On resistant Tx2752/Tx2783, leaf injury and yield decline were not seen or less severe than on its paired susceptible Tx2752/Tx430. Aphids declined on Tx2752/Tx2783 after initial colony establishment (Corpus Christi) or took about 60% longer to double in population size when compared with Tx2572/Tx430 (Winnsboro). The predominant natural enemy taxa were aphelinid mummies (Hymenoptera: Aphelinidae), ladybird beetles (Coleoptera: Coccinellidae), and sryphid flies (Diptera: Syrphidae), and they were more prevalent during flowering than prior to flowering. They were generally responsive to changes in aphid density of both susceptible and resistant hybrids, but variability points to need for further study. In future research, full season observations should continue as well as more detailed study of potential compatibility of sorghum resistance and biological control.

Sugarcane Aphid (Hemiptera: Aphididae): A New Pest on Sorghum in North America.

In 2013, the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), a new invasive pest of sorghum species in North America, was confirmed on sorghum in 4 states and 38 counties in the United States. In 2015, the aphid was reported on sorghum in 17 states and over 400 counties as well as all sorghum-producing regions in Mexico. Ability to overwinter on living annual and perennial hosts in southern sorghum-producing areas and wind-aided movement of alate aphids appear to be the main factors in its impressive geographic spread in North America. Morphological characteristics of the sugarcane aphid include dark tarsi, cornicles, and antennae, allowing easy differentiation from other aphids on the crop. Sugarcane aphid damages sorghum by removing sap and covering plants with honeydew, causing general plant decline and yield loss. Honeydew and sooty mold can disrupt harvesting. The aphid’s high reproductive rate on susceptible sorghum hybrids has resulted in reports of yield loss ranging from 10% to greater than 50%. In response, a combination of research-based data and field observations has supported development of state extension identification, scouting, and treatment guides that aid in initiating insecticide applications to prevent yield losses. Highly efficacious insecticides have been identified and when complemented by weekly scouting and use of thresholds, economic loss by sugarcane aphid can be minimized. Some commercial sorghum hybrids are partially resistant to the aphid, and plant breeders have identified other lines with sugarcane aphid resistance. A very diverse community of predators and parasitoids of sugarcane aphid has been identified, and their value to limit sugarcane aphid population growth is under investigation.