Parasitoid Distribution and Parasitism of the Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) in Different Maize Producing Regions of Uganda

Natural Enemies of the fall armyworm (Spodoptera frugiperda Smith) and comparing Neem aqueous extracts with its larvae, Gurage zone, central Ethiopia

The fall armyworm (Spodoptera frugiperda Smith) is an invasive and polyphagous insect pest. It poses a significant threat to maize crops, uncontrolled infestation can result 100 % loss. However, natural enemies play a vital role in regulating the population of this pest. Additionally, botanical sources extracts have the potential to be effective insecticides. The objectives of the study were to investigate the natural enemies of S. frugiperda in the Gurage zone and to compare efficacy of Neem seed and leaf aqueous extracts with S. frugiperda larvae, central Ethiopia. S. frugiperda larvae and egg masses, cocoons and larvae cadavers collected from infested maze farms. From each round collection 25 healthy and inactive larvae were sampled to rear until emerging adults. Observed predator species recorded. Neem seed and leaf aqueous extracts was tested against S. frugiperda in laboratory condition. The study found a diverse range of natural enemies associated with S. frugiperda, including parasitoids, predators, and entomopathogenic fungi. Three species of parasitoids (Exorista xanthaspis, Tachina spp., and Charops annulipes) were documented in Ethiopia for the first time. Predatory insects belonging to four distinct orders: Hemiptera, Dermaptera, Coleoptera, and Mantodea also identified. In particular, various Hemipterans were observed in the maize farms infested with S. frugiperda. In terms of Neem seed and leaf aqueous extracts, they demonstrated similar mortality rates for S. frugiperda larvae after 72 h, although differences were observed at 24 and 48 h. For effective management of S. frugiperda, more research is needed to fully exploit the potential of natural enemies and botanical source insecticides.

Farmer perceptions, knowledge, and management of fall armyworm in maize production in Uganda

Spodoptera frugiperda (J.E. Smith), fall armyworm (FAW), a polyphagous Noctuid pest, was first reported in Uganda in 2016. Farmers were trained to identify and manage the pest, but there was a lack of information on farmer knowledge, perceptions and practices deployed to control it. Therefore, we conducted a survey to assess maize farmers' knowledge, perceptions and management of the pest during the invasion. We interviewed 1,289 maize farmers from 10 maize-growing agro-ecological zones (AEZ) of Uganda using well-structured questionnaires. The data were analyzed using R version 4.2.3. The respondents faced many constraints, including pests, drought, poor soils and labor constraints. Among the pests, FAW was ranked by most (85%) of the respondents as the number one pest problem in maize, and some farmers reported having noticed it way back in 2014. By 2018, more than 90% of the farmers had seen or heard about FAW, and about 80% saw FAW in their fields. The most common FAW symptoms reported by maize farmers were windowing, near tunnel damage, and holes on the cobs. The developmental stages of FAW identified by farmers included eggs (10%), young larvae (78.7%), mature larvae (73.5%) and adult moths (6.7%). Insecticides were the major control tactic, although some farmers used plant extracts, hand-picking, sand, and ash. Farmers sourced information on FAW from various sources, including fellow farmers, radio/TV, extension agents, input dealers, print media, research and NGO extension. There is a need to package clear and uniform information for the farmers and to develop and promote a sustainable solution for FAW management, including harnessing biological control and cultural practices.

A Case of Myiasis Caused by Cordylobia anthropophaga (Diptera: Calliphoridae) in an Italian Traveler Returning from Senegal

PURPOSE

Myiases are infestations of human and animal tissues by fly larvae. These conditions are widespread in tropical countries and travelers in those areas are at risk of becoming infested. Although Cordylobia anthropophaga (Blanchard & Berenger-Feraud, 1872) is one of the most common myiasis-causing species, few high-quality images and molecular sequences are available for this fly. We present a case of C. anthropophaga infestation in an Italian patient returning from Senegal, with the aim of increasing both visual and molecular data for this species.

METHODS

After removal, the larva was determined following standardized morphological keys and photographed under a digital microscope. Molecular characterization of the Cytochrome c oxidase subunit I (COI) was performed using universal primers.

RESULTS

The general appearance, the structural organization of the cephalic region, of the cephaloskeleton, and of the posterior tracheal spiracles suggested that the causative agent of the myiasis was a third instar larva of C. anthropophaga. The morphological data are further supported by the molecular data: the COI sequence showed high levels of identity with the already published verified COI sequences of C. anthropophaga.

CONCLUSION

We provide high-quality morphological and molecular data useful for the identification of larvae of C. anthropophaga. We highlight that myiasis might be common in Senegal and better data about its prevalence in travelers and in the endemic countries are needed to understand the burden of this condition.

Hymenopteran parasitoid complex and fall armyworm: a case study in eastern India

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) has significantly affected maize crop yields, production efficiency, and farmers' incomes in the Indian Eastern Gangetic Plains region since it was first observed in India in 2018. A lack of awareness by maize growers of the appropriate selection, method, and timing of insecticide application not only creates a barrier to sustainable FAW control but also contributes to increased environmental pollution, reduced human health and increased production costs. We demonstrated that FAW inflicted the most damage in early whorl growth stage of maize, regardless of whether chemical insecticides were applied. FAW egg masses and larvae collected from maize fields in which no insecticides had been sprayed showed high parasitism rates by parasitoid wasps; in contrast fields that had been sprayed had much lower rates of parasitism on FAW. Ten hymenopteran parasitoids were observed in maize fields across the study region, suggesting a diversity of natural methods to suppress FAW in maize at different growth stages. These included two FAW egg parasitoids and eight FAW larval parasitoids. Microplitis manilae Ashmead was the most abundant FAW larval parasitoid species, and Telenomus cf. remus was the dominant FAW egg parasitoid species. Endemic FAW parasitoids such as those observed in this study have great potential as part of a sustainable, cost-effective agroecological management strategy, which can be integrated with other methods to achieve effective control of FAW.

Abundance, diversity and richness of natural enemies of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), in Zambia

The fall armyworm (FAW), Spodoptera frugiperda, an invasive pest originating from the Americas is a serious pest threatening cereal production and food security in Zambia. We studied the prevalence and abundance of natural enemies of FAW in three Agroecological regions (AERs I, II, and III) to identify those that could potentially serve as bio-control agents. Sampling of FAW parasitoids and predators was done along trunk roads at intervals of 10 km. Molecular sequence analysis and morphological characterization were used to identify natural enemies. Over 11 species of FAW natural enemies, including egg, egg-larval, and larval parasitoids, and predators, were identified in Zambia. The mean number of natural enemies and species richness was higher in AER I and IIa. Consequently, egg parasitism was highest in those two regions, at 24.5% and 12.2%, respectively. Larvae parasitism was highest in AER I (4.8%) and AER III (1.9), although no significant differences were observed. The most abundant and widely distributed parasitoid was Drino sp. (Diptera: Tachinidae), while Rhynocoris segmentarius (Germar) (Hemiptera: Reduviidae) and Belanogaster sp. (Hymenoptera: Vespidae) were the most prevalent predators. Our study reveals the presence of two natural enemies belonging to the genus Tiphia and Micromeriella, uncommon to FAW. Significant differences in the number of parasitoids were observed in polycropping, with the highest recovery of 12 ± 10% from maize + cowpeas + pumpkin and watermelon mixed cropping. The higher the rainfall, the lower the number of natural enemies recorded. Variations in rainfall patterns which affect FAW availability, cropping systems and the three AERs may explain natural enemies' species diversity in Zambia. The information provided in this study can aid the development of a national biological control programme for sustainable management of fall armyworm.

The Maize Caterpillar Mythimna (= Leucania) loreyi (Duponchel, 1827) (Lepidoptera: Noctuidae): Identification, Distribution, Population Density and Damage in Tunisia

Surveys were conducted during 2020 and 2021 to study the emerging lepidopteran pests inflicting cereals in Tunisia, with specific emphasis on maize and sorghum crops. A species was collected from traps placed in the Jendouba, Bizerte, Nabeul and Gabes regions. Thus, this study carried out first report on its identification, distribution, population density and damage. Results showed that M. loreyi was abundant in all prospected areas, with total adult captures reaching 4779 and 9499 moths on sorghum and maize, respectively, during 2020. Moreover, the mean infestation percentage reached its maximum during August at 31.05% and 20.69% for the Jendouba and Bizerte regions, respectively, while the highest infestations were observed in the Gabes and Nabeul regions during July, with respective mean values of 13.54% and 21.35%. In addition, results revealed that the highest pest incidence occurred in the Gabes region, with values of 11.1 ± 0.47 and 5.7 ± 0.48 during 2020 and 2021, respectively. Additionally, results pointed out that M. loreyi achieved two summer generations in the different localities of Tunisia. Overall, this study provides basic insights into the ecology and population biology of M. loreyi, which are required to establish an effective pest control program.

Virulence of Beauveria sp. and Metarhizium sp. fungi towards fall armyworm (Spodoptera frugiperda)

The development of effective pest management strategies for Spodoptera frugiperda is a high priority for crop protection across its invasive ranges. Here, we examined six Beauveria and five Metarhizium fungal isolates against this pest. Two Beauveria isolates (B-0571, B-1311) induced high mortality toward 3rd and 6th instar caterpillars and adults. For B-0571 mortality was 82.81 ± 5.75%, 61.46 ± 6.83%, and 93.75 ± 3.61%, and 73.72 ± 2.51%, 71.88 ± 5.41%, and 97.92 ± 2.08% for B-1311, with deaths in caterpillars largely occurring under 24 h (3rd instar control 0.74 ± 0.33%, B-0571 73.96 ± 7.85% and B-1311 62.08 ± 3.67%; 6th instar control 0%, B-0571 66.67% ± 11.02% and B-1311 62.5% ± 9.55%). Infection from both Beauveria isolates fully prevented reproduction in surviving S. frugiperda females. In contrast, all five Metarhizium isolates tested and the remaining four Beauveria isolates exhibited lower virulence. The discovery of two highly virulent Beauveria fungal isolates to S. frugiperda opens avenues to develop novel biological control tools against this highly invasive pest.

Prospects for classical biological control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in invaded areas using parasitoids from the Americas

Fall armyworm, Spodoptera frugiperda (J.E. Smith) is a polyphagous agricultural pest threatening food security worldwide. This American species recently invaded most of Africa, many Asian countries, and Oceania, where it mainly damages maize. Classical biological control (CBC) through the introduction of natural enemies from its area of origin is considered as a potential management approach. The paper reviews the prospects and constraints of a CBC programme against S. frugiperda using larval parasitoids, which are considered the most suitable natural enemies for introduction against this pest. The most important larval parasitoids in its native range are presented and discussed for their suitability as CBC agents, based the following criteria: their frequency of occurrence and parasitism levels, specificity, climatic suitability and absence of closely related species parasitizing S. frugiperda in the area of introduction. The ichneumonid Eiphosoma laphygmae Costa-Lima (Hymenoptera: Icheumonidae) is considered as a potential candidate for introduction because of its specificity and its importance as a parasitoid of the pest in most of its native range. The most frequent and important parasitoid of S. frugiperda in the Americas, the braconid Chelonus insularis Cresson (Hymenoptera: Braconidae), would most probably contribute to the control of S. frugiperda if released in invaded areas. However, it is oligophagous and would most certainly parasitize nontarget species. Before introducing C. insularis, or any other parasitoid species, the potential nontarget effects will have to be assessed and the risks will have to be weighed against the benefits of improving the natural control of this important pest.

Bio-Intensive Tactics for the Management of Invasive Fall Armyworm for Organic Maize Production

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an invasive pest native to the American continent. The present study focused on bio-intensive tactics like intercropping, using natural enemies, botanical insecticides and biopesticides for managing S. frugiperda for the organic production of maize in Indian conditions. A total of eight different parasitoids attacking the different stages of S. frugiperda viz., eggs and larvae were found in the study area. The total parasitism rate due to all the parasitoids ranged from 28.37 to 42.44%. The egg-larval parasitoid, Chelonus formosanus Sonan (Hymenoptera: Braconidae) was the dominant parasitoid (12.55%), followed by Chelonus nr. blackburni (Hymenoptera: Braconidae) (10.98%) and Coccygydium sp. (4.85%). About 36.58 percent of the egg masses collected was parasitized by egg parasitoids, among which Telenomus remus (Nixon) (Hymenoptera: Scelionidae) was the dominant parasitoid. The botanicals insecticides such as citronella and annona extract were most effective, resulting in 100% mortality of FAW larvae (168 h after treatment). The essential oil of garlic (100%) was found highly effective in inhibiting egg hatching, followed by geraniol (90.76%). The maize intercropped with lady's finger (okra) recorded significantly the lowest pest infestation and recorded higher grain yield (6.17 q/ha) than other intercropping systems and control (5.10 q/ha). The overall bioefficacy of commercial biopesticides against the larvae of S. frugiperda was in the following order azadirachtin > Metarhizium anisopliae (Metch.) Sorokin (Hypocreales: Clavicipitaceae) > Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) at 168 h after treatment.

Spodoptera frugiperda: Ecology, Evolution, and Management Options of an Invasive Species

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera, Noctuidae), is a well-known agricultural pest in its native range, North and South America, and has become a major invasive pest around the globe in the past decade. In this review, we provide an overview to update what is known about S. frugiperda in its native geographic ranges. This is followed by discussion of studies from the invaded areas to gain insights into S. frugiperda's ecology, specifically its reproductive biology, host plant use, status of insecticide resistance alleles, and biocontrol methods in native and invasive regions. We show that reference to host strains is uninformative in the invasive populations because multidirectional introduction events likely underpinned its recent rapid spread. Given that recent genomic analyses show that FAW is much more diverse than was previously assumed, and natural selection forces likely differ geographically, region-specific approaches will be needed to control this global pest.

Identification of Chelonus sp. from Zambia and Its Performance on Different Aged Eggs of Spodoptera frugiperda

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a migratory pest endemic, to tropical and subtropical regions of America. Biological control can effectively and sustainably control pests over a long period of time while reducing the frequency of pesticide use and ensuring the safety of agricultural produce. In our study, the egg-larval Chelonus species (Chelonus bifoveolatus) from parasitized eggs of Spodoptera frugiperda in Zambia were described and identified based on morphological and genetic characteristics. To evaluate the efficiency of C. bifoveolatus, their parasitism suitability on 0- to 2-day FAW eggs under laboratory conditions was compared. The results showed that C. bifoveolatus could accept all FAW eggs at 0-, 1- and 2-day-old age and complete development successfully. Significant differences were found among 0-, 1-, and 2-day-old host eggs with respect to egg-larva developmental duration of C. bifoveolatus, and the egg-larva developmental duration on 2-day-old eggs was significantly lower than those on 0- and 1-day-old eggs. No significant differences were observed in the parasitism, pupation, emergence, and female rates for C. bifoveolatus on various age eggs of FAW. Generally, the parasitism rate, pupal rate, and emergence rate at various ages of FAW eggs were higher than 90%, 75%, and 82%, respectively, and the longevity of female parasitoids was longer than male parasitoids, and the sex ratio of females to males was nearly 1:1. Our results indicate that C. bifoveolatus performed well on various ages of FAW eggs and is a potential biological control agent against FAW in Africa.

Integrated management of Spodoptera frugiperda 6 years post detection in Africa: a review

The introduction of fall armyworm (FAW) Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) on the African continent has led to paradigm shifts in pest control in maize systems, occasioned by year-round populations. The discovery of resident parasitoid species adapting to the new pest significantly informed decision-making toward avoiding highly hazardous synthetic insecticides to control the pest. A number of biopesticides have shown promise against the fall armyworm, providing a new arsenal for the sustainable management of this invasive pest. However, a few knowledge gaps remain for a fully integrated and sustainable FAW-management approach, particularly on host-resistance potential.

Population Genetic Structure of the Bean Leaf Beetle Ootheca mutabilis (Coleoptera: Chrysomelidae) in Uganda

Bean leaf beetle (BLB) (Ootheca mutabilis) has emerged as an important bean pest in Uganda, leading to devastating crop losses. There is limited information on the population genetic structure of BLB despite its importance. In this study, novel microsatellite DNA markers and the partial mitochondrial cytochrome oxidase subunit I (mtCOI) gene sequences were used to analyze the spatial population genetic structure, genetic differentiation and haplotype diversity of 86 O. mutabilis samples from 16 (districts) populations. We identified 19,356 simple sequence repeats (SSRs) (mono, di-, tri-, tetra-, penta-, and hexa-nucleotides) of which 81 di, tri and tetra-nucleotides were selected for primer synthesis. Five highly polymorphic SSR markers (4-21 alleles, heterozygosity 0.59-0.84, polymorphic information content (PIC) 50.13-83.14%) were used for this study. Analyses of the 16 O. mutabilis populations with these five novel SSRs found nearly all the genetic variation occurring within populations and there was no evidence of genetic differentiation detected for both types of markers. Also, there was no evidence of isolation by distance between geographical and genetic distances for SSR data and mtCOI data except in one agro-ecological zone for mtCOI data. Bayesian clustering identified a signature of admixture that suggests genetic contributions from two hypothetical ancestral genetic lineages for both types of markers, and the minimum-spanning haplotype network showed low differentiation in minor haplotypes from the most common haplotype with the most common haplotype occurring in all the 16 districts. A lack of genetic differentiation indicates unrestricted migrations between populations. This information will contribute to the design of BLB control strategies.

Designing a Pest and Disease Outbreak Warning System for Farmers, Agronomists and Agricultural Input Distributors in East Africa

Simple Summary

Designing early warning systems for threats to food crops in Africa must respond to the needs of potential users of the system. This paper provides evidence from professional distributors, retailers, researchers, and agronomists in East Africa who may be able to use and communicate the results of the predictive modeling of pest outbreaks. Understanding the timing and spatial extent of required warnings will help guide research and engagement in these rapidly commercializing countries.

Abstract

Early warnings of the risks of pest and disease outbreaks are becoming more urgent, with substantial increases in threats to agriculture from invasive pests. With geospatial data improvements in quality and timeliness, models and analytical systems can be used to estimate potential areas at high risk of yield impacts. The development of decision support systems requires an understanding of what information is needed, when it is needed, and at what resolution and accuracy. Here, we report on a professional review conducted with 53 professional agronomists, retailers, distributors, and growers in East Africa working with the Syngenta Foundation for Sustainable Agriculture. The results showed that respondents reported fall armyworm, stemborers and aphids as being among the most common pests, and that crop diversification was a key strategy to reduce their impact. Chemical and cultural controls were the most common strategies for fall armyworm (FAW) control, and biological control was the least known and least used method. Of the cultural control methods, monitoring and scouting, early planting, and crop rotation with non-host crops were most used. Although pests reduced production, only 55% of respondents were familiar with early warning tools, showing the need for predictive systems that can improve farmer response.

Assessing the Potential of Inoculative Field Releases of Telenomus remus to Control Spodoptera frugiperda in Ghana

In response to the threat caused by the fall armyworm to African maize farmers, we conducted a series of field release studies with the egg parasitoid Telenomus remus in Ghana. Three releases of ≈15,000 individuals each were conducted in maize plots of 0.5 ha each in the major and minor rainy seasons of 2020, and compared to no-release control plots as well as to farmer-managed plots with chemical pest control. No egg mass parasitism was observed directly before the first field release. Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season, while 72-100% of egg masses were parasitized in the minor rainy season, during which pest densities were much lower. However, no significant difference in egg mass parasitism was found among the T. remus release plots, the no-release control plots and the farmer-managed plots. Similarly, no significant decrease in larval numbers or plant damage was found in the T. remus release fields compared to the no-release plots, while lower leaf and tassel damage was observed in farmer-managed plots. Larval parasitism due to other parasitoids reached 18-42% in the major rainy season but was significantly lower in the minor rainy season, with no significant differences among treatments. We did not observe significant differences in cob damage or yield among the three treatments. However, the lack of any significant differences between the release and no-release plots, which may be attributed to parasitoid dispersal during the five weeks of observation, would require further studies to confirm. Interestingly, a single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus and, thus, merits further investigation in the context of developing IPM strategies against FAW.