Fall Armyworm Populations Research Articles

Revisiting fall armyworm population movement in the United States and Canada.

Biophysical approaches validated against haplotype and trap catch patterns have modeled the migratory trajectory of fall armyworms at a semi-continental scale, from their natal origins in Texas or Florida through much of the United States east of the Rocky Mountains. However, unexplained variation in the validation analysis was present, and misalignments between the simulated movement patterns of fall armyworm populations and the haplotype ratios at several locations, especially in the northeastern US and Canada, have been reported. Using an expanded dataset extending into Canada, we assess the consistency of haplotype patterns that relate overwintered origins of fall armyworm populations to hypothesized dispersal trajectories in North America and compare the geographic distribution of these patterns with previous model projections. We confirm the general accuracy of previous modeling efforts, except for late in the season where our data suggests a higher proportion of Texas populations invading the northeast, extending into eastern Canada. We delineate geographic limits to the range of both overwintering populations and show that substantial intermixing of the Texas and Florida migrants routinely occurs north of South Carolina. We discuss annual variation to these migratory trajectories and test the hypothesis that the Appalachian Mountains influence geographic patterns of haplotypes. We discuss how these results may limit gene flow between the Texas and Florida natal populations and limit the hereditary consequences of interbreeding between these populations.

Genetic analyses and detection of point mutations in the acetylcholinesterase-1 gene associated with organophosphate insecticide resistance in fall armyworm (Spodoptera frugiperda) populations from Uganda

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda; J.E. Smith (Lepidoptera: Noctuidae), is now an economically important pest that causes huge losses to maize productivity in sub-Saharan Africa. Variations in sub-population genetics and the processes of rapid adaptation underpinning the invasion remain unclear. For this, the genetic identity and diversity of FAW populations in Uganda were revealed by sequencing 87 samples (collected across the country). Based on the partial mitochondrial cytochrome oxidase I (COI) gene polymorphisms, we further examined the mitochondrial haplotype configuration and compared the FAW in Uganda with sequences from other parts of the world. The molecular target for organophosphate and carbamate resistance, acetylcholinesterase, was also investigated.ResultsAnalysis of the partial COI gene sequences showed the presence of both rice (predominant) and corn strain haplotypes, with a haplotype diversity of 0.382. Based on the COI marker, pairwise difference distribution analyses, and neutrality tests, showed that the FAW populations in Uganda and the rest of Africa are evolving neutrally, but those in America and Asia are undergoing expansion. Our findings support observations that invasive FAW populations throughout the rest of Africa and Asia share a common origin. Sequencing of the S. frugiperda ace-1 gene revealed four amino acid substitutions, two of which (A201S and F290V) were previously shown to confer organophosphate resistance in both S. frugiperda and several other insect species. The other two previously reported new variations in positions g-396 and g-768, are presumed to be related to the development of insecticide resistance.ConclusionsThis research has increased our knowledge of the genetics of FAW in Uganda, which is critical for pest surveillance and the detection of resistance. However, due to the low gene polymorphism of COI, more evolutionary studies incorporating the Spodoptera frugiperda whole-genome sequence are required to precisely understand the FAW population dynamics, introduction paths, origin, and subsequent spread.

Performance of the domestic Bt corn event expressing pyramided Cry1Ab and Vip3Aa19 against the invasive Spodoptera frugiperda (J. E. Smith) in China.

The invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), has caused serious corn yield losses and increased the frequency of insecticide spraying on corn in Africa and Asia. Drawing lessons from the use of Bt corn to manage fall armyworm in the Americas, China released a certificate for the genetically modified corn event DBN3601T pyramidally expressing Cry1Ab and Vip3Aa19 for industrialization in 2021. Performance of the DBN3601T event against invasive fall armyworm in China was evaluated by plant tissue-based bioassays and field trials during 2019-2021. In the bioassays, tissues and organs of DBN3601T corn differed significantly in lethality to fall armyworm neonates in the order: leaf > husk > tassel and kernel > silk. In field trials, compared with non-Bt corn, DBN3601T corn greatly suppressed fall armyworm populations and damage; larval density, damage incidence, and leaf damage scores for DBN3601T corn were significantly lower than for non-Bt corn at different vegetative stages, and efficacy against larval populations during the 3 years ranged from 95.24% to 98.30%. A laboratory bioassay and 3-year field trials confirmed that DBN3601T corn greatly suppressed fall armyworm populations and has high potential as a control of this invasive pest, making it a key tactic for integrated management of fall armyworm in China. © 2022 Society of Chemical Industry.

Host-plant adaptation as a driver of incipient speciation in the fall armyworm (Spodoptera frugiperda)

BackgroundDivergent selection on host-plants is one of the main evolutionary forces driving ecological speciation in phytophagous insects. The ecological speciation might be challenging in the presence of gene flow and assortative mating because the direction of divergence is not necessarily the same between ecological selection (through host-plant adaptation) and assortative mating. The fall armyworm (FAW), a major lepidopteran pest species, is composed of two sympatric strains, corn and rice strains, named after two of their preferred host-plants. These two strains have been hypothesized to undergo incipient speciation, based on (i) several lines of evidence encompassing both pre- and post-zygotic reproductive isolation, and (ii) the presence of a substantial level of genetic differentiation. Even though the status of these two strains has been established a long time ago, it is still yet to be found whether these two strains indeed exhibit a marked level of genetic differentiation from a large number of genomic loci. Here, we analyzed whole genome sequences from 56 FAW individuals either collected from pasture grasses (a part of the favored host range of the rice strain) or corn to assess the role of host-plant adaptation in incipient speciation.ResultsPrincipal component analysis of whole genome data shows that the pattern of divergence in the fall armyworm is predominantly explained by the genetic differentiation associated with host-plants. The level of genetic differentiation between corn and rice strains is particularly marked in the Z chromosome. We identified one autosomal locus and two Z chromosome loci targeted by selective sweeps specific to rice strain and corn strain, respectively. The autosomal locus has both increased DXY and FST while the Z chromosome loci had decreased DXY and increased FST.ConclusionThese results show that the FAW population structure is dominated by the genetic differentiation between corn and rice strains. This differentiation involves divergent selection targeting at least three loci, which include a locus potentially causing reproductive isolation. Taken together, these results suggest the evolutionary scenario that host-plant speciation is a driver of incipient speciation in the fall armyworm.

Evaluation of Beauveria Bassiana, Neem Oil and Selected Insecticides on Population of Fall Armyworm Spodoptera frugiperda (J. E. Smith) on Maize (Zea mays L.)

A field trail was conducted at Crop Research Farm (CRF) SHUATS Naini, Prayagraj, during kharif 2021 in Randomized block design with seven treatments viz, Imidacloprid 17.8% SL Thiodicarb75%WP,Spinosad 45% SC, Emamectin benzoate 5% SG, Neem oil, Beauveria bassiana 1x108 CFU/ml, Thiamethoxam 12.6% + Lambda cyhalothrin 9.5% ZC and untreated control in three replication. Data were taken on fall armyworm population. The larval population of fall armyworm Spodoptera frugiperda (J.E.Smith) on three, seven and fourteen days after spraying revealed that the treatment Emamectin benzoate 5% SG (5.15) proved to be the most effective treatment followed by Thiodicarb75%WP (6.44), Thiamethoxam 12.6% + Lambda cyhalothrin 9.5% ZC (7.41), Spinosad 45% SC (8.23), Imidacloprid 17.8%SL (8.79), whereas Neem oil 3% (10.24) and B. bassiana 1x108 CFU/ml (10.93) were of least effective against Spodoptera frugiperda. Plot treated with Emamectin benzoate 5% SG showed highest yield (35.31q/ha), followed by Thiodicarb75% WP (34.21q/ha), Thiamethoxam 12.6% + Lambda cyhalothrin 9.5% ZC (32.58q/ha), Spinosad 45% SC (32.08q/ha), Imidacloprid 17.8% SL (31.21qt/ha), Neem oil 3% (29.63q/ha) and B.bassiana 1x108 CFU/ml (28.02), as compared to control (22.44q/ha).

Comparative analysis of gut microbiota and immune genes linked with the immune system of wild and captive Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is one of the most highly polyphagous invasive pests causing serious damage to maize crops in China. However, little is known about the gut immune responses to the environment, particularly along the migration routes in Jianghuai, China, throughout the autumn and winter. In this study, high-throughput sequencing and real-time quantitative PCR (RT-qPCR) were employed to examine the variations in immune genes and gut microbiome communities between captive and wild fall armyworm populations. Results showed that the diversity and community of the gut's microbes were higher in wild populations, and the average weighted UniFrac distance between bacterial taxa varied. A wide variety of immune genes were more abundant in the wild populations than in others. Results indicated that diets and different survival conditions impacted the gut microbiota and immune system of S. frugiperda, which was crucial for environmental adaptation. These differences in gut microbiota and immune responses between wild and captive Fall armyworms are critical for comprehending the symbiotic relationship between microbes, immune genes, and hosts. They also highlight the need for increased focus on developing more effective and environmentally friendly pest control methods.

Evidence of field-evolved resistance in Spodoptera frugiperda (Lepidoptera: Noctuidae) to emamectin benzoate in Brazil

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith, 1797), has evolved resistance to several insecticides and Bacillus thuringiensis Berliner (Bt) toxins expressed in transgenic plants worldwide. Recently, we demonstrated a high risk of resistance evolution of a laboratory-selected emamectin benzoate-resistant strain of FAW based on incomplete dominant inheritance. In this study, we presented laboratory studies that established the baseline susceptibility and defined a diagnostic concentration of emamectin benzoate for the FAW performed in 2002. Then, resistance to emamectin benzoate was monitored in field-collected populations of FAW in Brazil from 2003 to 2004 and 2019 to 2021 using different methods: (i) estimating concentration-mortality curves; (ii) determining larval survival at a diagnostic concentration of emamectin benzoate; and (iii) assessing its survivorship on maize leaves sprayed with the field rate of this insecticide. Populations of FAW presented similar susceptibility to emamectin benzoate in 2002 (LC50 from 0.25 to 0.44 μg a.i./mL) and 2003/04 (LC50 from 0.13 to 0.43 μg a.i./mL), not differing from the susceptible reference population (LC50 of 0.22 μg a.i./mL). From 2003 to 2004, larval survival at the diagnostic concentration of emamectin benzoate of 3.2 μg a.i./mL was <1.79%. From 2019 to 2021, the susceptibility to emamectin benzoate in field populations of FAW decreased, with LC50 values ranging from 0.78 to 158.0 μg a.i./mL, indicating resistance ratios up to 632-fold. Larval survival at a diagnostic concentration of emamectin benzoate also increased, reaching up to 81.4%. Larval survival on maize leaves sprayed with the field rate of emamectin benzoate ranged from 16.6 to 88.5% in populations of FAW collected in 2021. Overall, our findings revealed significant shifts towards decrease in the susceptibility to emamectin benzoate in Brazilian populations of FAW, providing robust evidence of field-evolved resistance.

Susceptibilities of the Invasive Fall Armyworm (Spodopterafrugiperda) to the Insecticidal Proteins of Bt maize in China

To control the fall armyworm (FAW), Spodoptera frugiperda (Smith), a serious threat to maize production in China, the Chinese government has issued biosafety certificates for transgenic insect-resistant maize expressing Bt (Bacillus thuringiensis) toxins including Bt-Cry1Ab maize (crop event DBN9936), Bt-Vip3Aa maize (event DBN9501), Bt-(Cry1Ab+Vip3Aa) maize with superimposed traits (event DBN9936 × DBN9501) and Bt-(Cry1Ab+Vip3Aa) maize with superimposed traits (event Bt11 × MIR162), but the susceptibility baselines of geographically distinct FAW populations to these events, which form the basis for managing resistance development in the pest to these events, are not clear. We used the diet-incorporated bioassays method to detect the susceptibilities of the seven FAW populations collected from Yunnan, Henan and Hubei provinces in China in 2021 to the insecticidal proteins of the four Bt maize events. The result showed that the susceptibilities of different geographical populations to Bt insecticidal proteins were significantly different. In the seven populations, the range in median lethal concentrations (LC50) of Cry1Ab expressed in DBN9936 was 0.87–2.63 μg/g, 0.14–0.30 μg/g for Vip3Aa expressed in DBN9501, 0.78–1.86 μg/g for Cry1Ab+Vip3Aa expressed in DBN9936 × DBN9501, and 0.36–1.42 μg/g for CryAb+Vip3Aa expressed in Bt11 × MIR162. The growth inhibition responses also showed that the susceptibilities varied with the different median growth inhibitory concentration (GIC50) ranges (0.38–1.22, 0.08–0.28, 0.28–0.87, and 0.24–0.78 μg/g, respectively). The variations in the ranges of the susceptibility baselines of the geographical populations of fall armyworm in China to the insecticidal proteins expressed in the four events provide a scientific basis for monitoring FAW population resistance to Bt maize and managing the populations using different Bt maize events.

Distribution characteristics of Spodoptera frugiperda (Lepidoptera: Noctuidae) winter populations in typical Mountain agricultural area of Southwest China

Fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the most damaging crop pests worldwide and has become a significant threat to the food security in many countries. The Lancang River (Mekong) valley and Nujiang River (Salween) valley, which are typical mountain agricultural areas located in the Hindu Kush-Himalayan (HKH) mountain range, are the key channels for the south to north migration of FAW in southwestern China. The purpose of this study was to analyze the population structure and distribution of FAW winter populations in the Lancang River and Nujiang River basins and relate these findings with respect to altitude, latitude, and mean monthly winter temperature in order to explore the spatial and temporal distribution characteristics of the winter population. Our results indicated that overwintering populations of FAW mainly appeared in winter cornfields with a few pupae found in summer cornfields near the middle and lower reaches of the Lancang River basin (south 26.04° N and below 1600 m) and the Nujiang River basin (south of 26.80° N and below 1500 m). Winter corn appeared to be a prerequisite for the occurrence of FAW in winter. The mean monthly temperature of the coldest month being greater than 10 °C is one critical factor determining where FAW populations will occur in winter. Some control options that could be used in these river basins include adjusting crop planting patterns and developing a large-scale non-host isolation band.

Annual dynamics of fall armyworm populations in West Africa and biology in different host plants

Since its recent introduction in West Africa, the fall armyworm Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) has severely damaged maize and other crops. Control efforts face many challenges as the knowledge on this invasive pest is still limited. In this study, we assessed the annual population dynamics by monitoring this species using pheromone traps and visual observations, so as to contribute to the development of an integrated management strategy. In addition, we also evaluated some life history traits of S. frugiperda on different local host plants to identify the most suitable hosts in Burkina Faso.Adult captures were recorded throughout the year, as a result of a favorable mean annual temperature (29°C). Two population peaks occured: one peak (15.5±3.1 adults per trap and per month) was recorded in December and January (dry season) while the second peak (17.5±2.5) occured in July and August (rainy season). These peaks were synchronized with the major maize production periods of the region, usually 1 to 2 months after planting, when the plants had 6 to 12 leaves. In addition, the proportion of infested maize fields and infested plants per field was higher in the dry season (94.0% and 44.9%) than in the rainy season (80.0% and 26.2%). Based on the larva to adult survival rate (65-80%), mean fecundity (700-1000 eggs per female) and short life span of 36-38 days, pearl millet, maize and groundnut were found the most suitable hosts for the insect development.To better manage this insect pest, we suggest monitoring efforts in all crops associated with maize, the use of short-cycle varieties and early planting. In addition, curative treatments are more effective when applied on young maize plants, as the early instars are the most susceptible.

Down-Regulation of P450 Genes Enhances Susceptibility to Indoxacarb and Alters Physiology and Development of Fall Armyworm, Spodoptera frugipreda (Lepidoptera: Noctuidae).

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a pest of many important crops globally. Effective control is challenging, with the pest exhibiting resistance to different synthetic pesticides across various groups. However, the mechanisms employed by resistant insects for overexpression of relevant detoxification genes remain unclear. The activity of detoxification enzymes was investigated in this study. Additionally, using RNA interference (RNAi), a functional analysis was completed of two P450s genes in an indoxacarb resistant population of fall armyworms. Elevated resistance levels (resistance ratio = 31.37-fold) in indoxacarb-selected populations of FAW were observed after 14 generations. The qRT-PCR showed higher expression of two cytochrome P450 genes, CYP321A7 and CYP6AE43, in this selected population compared to the control population. RNAi was applied to knock down the P450 dsCYP321A7 and dsCYP6AE43 genes in the FAW larvae. Droplet feeding of the dsRNAs (CYP321A7 and CYP6AE43) via an artificial diet significantly increased mortality rates in the indoxacarb treated population. A shorter larval developmental time of FAW was detected in all dsRNAs-fed larvae. Correspondingly, larval mass was reduced by dsRNAs in indoxacarb resistant populations of fall armyworm. Larval feeding assays demonstrate that dsRNAs targeting, specifically of CYP321A7 and CYP6AE43 enzymes, could be a beneficial technique in the management of indoxacarb resistant populations. Further study on the potential use of dsRNA and its application should be conducted in efforts to counter the development of resistance in FAW against various insecticides in the field.

Sodium chloride reduces the viability of eggs, larvae, and pupae of Spodoptera frugiperda, as well as delays its development

The control of fall armyworm (Spodoptera frugiperda) populations involves the application of pesticides that cause several unwanted effects to humans and other animals, as well as to environment. Sodium chloride (NaCl) has been used in agriculture to potentiate the toxicity of pesticides. Here, the effects of NaCl on the viability of eggs, larvae, and pupae, as well as on development of S. frugiperda were evaluated. The treatment with 0.15 M NaCl caused a 35% reduction of egg hatching and the ingestion of artificial diet containing the salt caused mortality of caterpillars, pre-pupae, and pupae, as well as delayed the development of the insects. The larval, pre-pupa and pupa stages were elongated by about 2, 1 and 0.8 days, respectively. Additionally, significant reduction in pupae body weight was recorded in groups treated with NaCl at 0.62 mg/g and 3.12 mg/g. Despite these effects, NaCl ingestion did not affect the viability of adults and their reproductive performance. Food deterrent assay revealed that the salt acted as a phagostimulant agent. In conclusion, NaCl reduces the hatching of S. frugiperda eggs and damage the survival of carterpillars and pupae, as well interferes with insect development.

The Effect of Resistance to Bt Corn on the Reproductive Output of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Simple SummaryThe use of transgenic crops expressing insecticidal proteins from Bacillus thuringiensis (Bt) has been a successful strategy to control the fall armyworm (FAW) Spodoptera frugiperda. However, resistance to many Bt proteins has been observed, which could reduce the effectiveness of this approach as a control strategy. In this study, we compared the reproductive traits of susceptible and resistant FAW males and females to determine if there are costs associated with resistance. Our data provided clear evidence that the development of resistance to the Bt protein affected the reproductive capacity of resistant FAW males.The fall armyworm (FAW) Spodoptera frugiperda is the most significant lepidopteran corn pest in South American countries. Transgenic Bt corn, producing the Cry1Fa toxins, has been used to control this pest, but there is clear evidence that some FAW populations have developed resistance. To determine if there are costs associated with resistance, we compared the mass of adults, the duration of mating, and the mass of the first spermatophore produced, as well as the lifetime fecundity and fertility of once-mated susceptible (SS) and resistant (RR) females. Adult mass was affected by both sex and strain, with SS females being significantly larger than RR ones, while the inverse was true for males. RR pairs took significantly longer to mate than SS pairs, yet the mass of spermatophores produced by RR males was significantly less than those of SS males. The total number of eggs laid did not differ but the fertility of eggs from once-mated RR pairs was significantly lower than that of SS pairs. Our data provided clear evidence that the development of Bt resistance affected the reproductive capacity of resistant FAW.

Self-limiting fall armyworm: a new approach in development for sustainable crop protection and resistance management

BackgroundThe fall armyworm, Spodoptera frugiperda, is a significant and widespread pest of maize, sorghum, rice, and other economically important crops. Successful management of this caterpillar pest has historically relied upon application of synthetic insecticides and through cultivation of genetically engineered crops expressing insecticidal proteins (Bt crops). Fall armyworm has, however, developed resistance to both synthetic insecticides and Bt crops, which risks undermining the benefits delivered by these important crop protection tools. Previous modelling and empirical studies have demonstrated that releases of insecticide- or Bt-susceptible insects genetically modified to express conditional female mortality can both dilute insecticide resistance and suppress pest populations.ResultsHere, we describe the first germline transformation of the fall armyworm and the development of a genetically engineered male-selecting self-limiting strain, OX5382G, which exhibits complete female mortality in the absence of an additive in the larval diet. Laboratory experiments showed that males of this strain are competitive against wild-type males for copulations with wild-type females, and that the OX5382G self-limiting transgene declines rapidly to extinction in closed populations following the cessation of OX5382G male releases. Population models simulating the release of OX5382G males in tandem with Bt crops and non-Bt ‘refuge’ crops show that OX5382G releases can suppress fall armyworm populations and delay the spread of resistance to insecticidal proteins.ConclusionsThis article describes the development of self-limiting fall armyworm designed to control this pest by suppressing pest populations, and population models that demonstrate its potential as a highly effective method of managing resistance to Bt crops in pest fall armyworm populations. Our results provide early promise for a potentially valuable future addition to integrated pest management strategies for fall armyworm and other pests for which resistance to existing crop protection measures results in damage to crops and impedes sustainable agriculture.

FALL ARMYWORM OUTBREAKS IN ASIA: ANALYZING THE STRATEGIES TO CONTROL

Fall armyworm (Spodoptera frugiperda) is a Lepidopteran moth of Noctuidae family. Due to its polyphagous characteristic with a large host range, strong migration ability, high fecundity (average egg production per female is about 1500) and lack of diapause has already contributed to its invasiveness in America and Africa. Recently it has been introduced in Asia in the year 2018. Though it has been only around three years of Fall armyworm (FAW) introduction, it has already spread into many Asian countries and on the way to cause havoc. Though it can infest many crops, its main target and maximum yield loss has occurred in case of Maize. In America and Africa, farmers are already well known to this pest and have adapted themselves to reduce crop loss to some extent by undertaking several management options. As this pest is completely new to Asia, farmers do not know much about its biology, nature of damage and control measures. And their misdiagnosis of the pest leads to panic and increased crop loss. Therefore, it is very important to increase awareness among the farmers to identify its attack on the right time to take suitable control measures as well as preventive measures for upcoming cropping seasons. Some of the cultural, mechanical, biological and chemical control measures those were effective in reducing its infestation outside Asia, has also found to be effective inside Asia. Collaboration of these control measures according to the field condition is main concern for the cultivators. But the integrated pest management option alone can also help to keep FAW population much below economic injury level and prevent its invasiveness as a tool of sustainable management for ensuring food security.

Areawide management of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), using selected cover crop plants

BackgroundFall armyworm, Spodoptera frugiperda (J. E. Smith) is a migratory moth that annually migrates northward each spring from sites in southern Florida and southern Texas. This caterpillar pest feeds on and damages row, turf and vegetable crops in the eastern and central U.S. Before migrating in spring, it feeds on cover crops in central and eastern Florida and expands its populations. Our objective was to use multi-year studies to compare fall armyworm populations that develop in cover crop plants.MethodsA series of field experiments and a laboratory feeding study were conducted to compare infestation and feeding and of fall armyworm on different cover crop plants. Field experiments had plots planted with corn (Zea mays L.), sorghum-sudangrass [Sorghum bicolor (L.) Moench], a standard cover crop in Florida, and two alternative cover crops, sunn hemp (Crotalaria juncea L.) and cowpea [Vigna unguiculata (L.) Walpers spp. unguiculata]. Another trial compared populations in sorghum-sudangrass and in mixtures of sorghum-sudangrass with buckwheat (Fagopyrum esculentum Moench) or pearl millet (Cenchrus americanus (L.) Morrone). Fall armyworm larvae were fed and allowed to develop on different sunn hemp germplasm in a laboratory trial.ResultsField populations of fall armyworm were highest on corn, followed by sorghum-sudangrass. Sunn hemp and cowpea had larval populations 70–96% less than on sorghum-sudangrass, suggesting replacement of this cover crop with either plant species might help reduce areawide populations of resident or migratory fall armyworm. Larvae collected from cover crop plots had parasitism levels that averaged 30%, with Chelonus insularis (Hymenoptera: Braconidae) emerging as the most commonly-collected species. Larval feeding on different sunn hemp germplasm lines resulted in no difference in weight gain.ConclusionsReplacing sorghum-sudangrass with sunn hemp varieties or germplasm should be acceptable as a replacement cover crop for areawide management of fall armyworm.

Estimation of Avoidable Yield loss in Maize Zea mays L. caused by the fall armyworm Spodoptera frugiperda (JE Smith) (Noctuidae: Lepidoptera)

Invasive fall armyworm Spodoptera frugiperda (JE Smith) (Noctuidae: Lepidoptera) has the potential to cause 70 – 80 per cent yield loss in maize. Field experiments to assess the avoidable yield loss due to invasive fall armyworm S. frugiperda (Noctuidae: Lepidoptera) was conducted across four major maize growing zones in Tamil Nadu, India. The treatments Complete Protection (T1), Window based insecticide application as per Tamil Nadu Agricultural University (TNAU) Integrated Pest Management capsule (T2) and Untreated Control (T3) were imposed in four maize zones of Tamil Nadu during 2020 - 21. In complete protection (T1) the recommended insecticides were applied as and when the incidence was noticed. Insecticides recommended for different widows viz., Azadirachtin 1% EC @ 2 ml/l. or Emamectin benzoate 5% SG @ 200 g ai/ ha for first window (15 – 20 days) and Spinetoram 11.7% w/w SC @ 30 g a.i/ha or Chlorantraniliprole 18.5% SC @ 40 g a.i/ha or Novaluron 10EC @ 100g a.i./ha were applied in the window based application (T2). The average avoidable yield loss for complete protection (T1) and window-based application (T2) was in the order Coimbatore &gt; Madurai &gt; Tirunelveli &gt; Tiruchirappalli. The average avoidable yield loss in complete protection (T1) and window based application (T2) was 2600.25 and 2307.87 kgs/ha respectively. The number of insecticide sprays required to keep the fall armyworm population under control was ranged between 3 to 4, in complete protection (T1) whereas in window-based application (T2) two sprays were given. The average difference in avoidable yield loss between window based (T2) and complete protection (T1) was 292.38kgs/ha. Both complete protection (T1) and window-based application (T2) recorded same benefit cost ratio of 1.65 and average per hectare plant protection cost of Rs.11000/- and Rs.5413/- respectively. The timely interventions at critical stages of maize growth will check the fall armyworm population from causing any economic damage to the maize. The crop care at critical stages will be the ideal strategy for the fall armyworm management.

Dynamics for a non-autonomous fall armyworm-maize interaction model with a saturation functional response.

In this study, we present a non-autonomous model with a Holling type II functional response, to study the complex dynamics for fall armyworm-maize biomass interacting in a periodic environment. Understanding how seasonal variations affect fall armyworm-maize dynamics is critical since maize is one of the most important cereals globally. Firstly, we study the dynamical behaviours of the basic model; that is, we investigate positive invariance, boundedness, permanence, global stability and non-persistence. We then extended the model to incorporate time dependent controls. We investigate the impact of reducing fall armyworm egg and larvae population, at minimal cost, through traditional methods and use of chemical insecticides. We noted that seasonal variations play a significant role on the patterns for all fall armyworm populations (egg, larvae, pupae and moth). We also noted that in all scenarios, the optimal control can greatly reduce the sizes of fall armyworm populations and in some scenarios, total elimination may be attained. The modeling approach presented here provides a framework for designing effective control strategies to manage the fall armyworm during outbreaks.

A fractional-order fall armyworm-maize biomass model with naturally beneficial insects and optimal farming awareness

Maize remains an important food crop in Africa. However, the production of this crop, and consequently the livelihood of the growers are threatened by the invasion and widespread infestation of the fall armyworm which causes substantial maize yield losses. In this paper, a fractional-order fall armyworm-maize biomass model with naturally beneficial insects and optimal farming awareness has been formulated. Comprehensive analysis of the model has shown that it contains five equilibrium points which are all locally and globally asymptotically stable if the conditions outlined in Lemma 2.1 and 2.2 are met. We also carried out numerical simulations to support the analytical results and to illustrate different dynamical regimes that can be observed in the model. We have found that time-dependent farming awareness can significantly reduce fall armyworm population if the cost of implementation is relatively low.

Identifikasi dan Efektivitas Berbagai Teknik Pengendalian Hama Baru Ulat Grayak Spodoptera frugiperda J. E. Smith pada Tanaman Jagung berbasis PHT- Biointensif

The presence of new pest Spodoptera frugperda J. E. Smith has the potential to reduce corn production, so its existence needs to be controlled. The aim of this research is to obtain control techniques that could reduce the intensity of S. frugiperda pest’s attack. The research was conducted from June to October 2020. The experiment was designed in a randomized block design (RBD) with 9 replications and 3 treatments consisting of non-control (NP), PHT-biointensive (BI), and synthetic pesticides. In BI treatment, neem leaf extract (25 mL/plot) and Beauveria bassiana (6,25 g/plot) were used. Meanwhile, the PS treatment used deltametrin active ingredient (3,125 mL/plot). The volume of spray used was 1,25 L. The results showed that PS control techniques gave the best results in suppressing the intensity of fall armyworm S. frugiperda attacks (0,57%-7,04%) followed by BI treatment (0%-6,89%) and NP (0,97%-8,29%). The highest pest populations overall were found in NP treatment and the lowest in PS treatment. PS treatment provided the highest production result with a cob weight of 18,6 kg/plot (24,81 tons/ha), while BI treatment of 17,00 kg/plot (22,72 tons/ha) and NP of 15,44 kg/plot (20,64 tons/ha). The results of the correlation test between the intensity of pest attacks and production results showed that the higher the pest attack, the lower the harvest weight produced. Therefore, pest control by using synthetic pesticides made from active deltametrin is declared effective in suppressing the intensity of attacks and populations of fall armyworm S. frugiperda and able to provide high production results.&#x0D; &#x0D; Keywords: corn, intensity of attack, Spodoptera frugiperda