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Trehalose is the most important carbohydrate in insects. It is required for chitin synthesis and, thus, insect growth and development. Trehalase is the only enzyme that catalyzes the decomposition of trehalose. Mythimna separata is an important pest of cereal crops. We cloned and identified Tre1 and Tre2 cDNA sequences in M. separata. Analysis of MsTre1 and MsTre2 expression revealed that MsTre1 was highly expressed in the midgut, and MsTre2 was highly expressed in the integument. The expression of MsTre1 and MsTre2 was the highest in the pupal stage. We used RNA interference to inhibit MsTre1 and MsTre2 expression. MsTre1 and MsTre2 silencing resulted in significant changes in the expression of genes associated with trehalose and chitin metabolism, and significantly reduced the MsTre1 and MsTre2 activity and the glucose and chitin content. Hematoxylin and eosin staining, and transmission electron microscopy showed that the silencing of MsTre1 slowed larval molting, and the new cuticle was significantly thinner in dsMsTre1-injected larvae than in control larvae. Overall, MsTre1 and MsTre2 are two effective genes in M. separata that regulate insect growth via the trehalose and chitin metabolism pathways, and MsTre1 is more important for cuticle formation in the epidermis than MsTre2. Trehalose is an important carbohydrate substance in insect hemolymph. Chitin is the main component of cuticle and peritrophic matrix in insects. Trehalase (Tre) catalyzes the decomposition of trehalose. Few studies of trehalase in lepidopteran insects have been conducted. Here, the functions of soluble Tre (Tre1) and membrane-bound Tre (Tre2) in the growth and development of Mythimna separata were investigated. We cloned and identified Tre1 and Tre2 cDNA sequences in M. separata. Analysis expression revealed that MsTre1 and MsTre2 were highly expressed in midgut and integument, respectively. The expression of MsTre1 and MsTre2 was highest in the pupal stage. We used RNA interference (RNAi) to inhibit Tre expression in M. separata larvae. Injection of dsMsTre1 or dsMsTre2 resulted in abnormal phenotypes and impeded normal molting. Silencing of MsTre1 and MsTre2 resulted in significant changes in the expression of genes in the trehalose and chitin metabolism pathways, significantly increased the trehalose and glycogen content, and significantly decreased MsTre1 and MsTre2 activity, the glucose content, and the chitin content in midgut and integument. Silencing of MsTre1 slowed larval molting, and the new cuticle was significantly thinner. These results indicate that RNAi of Tre may be useful for control strategies against M. separata.

Maize is the most essential crop of China and its productivity has been recently endangered by the fall armyworm (FAW), Spodoptera frugiperda. Chemical pesticides are one of the most important strategies for managing FAW on a short-term basis. The seven synthetic insecticides including novel and conventional belong to four chemical group, spinetoram and spinosad (spinosyns), lambda-cyhalothrin, cypermethrin and bifenthrin (pyrethroids), abamectin (avermectins), broflinilide (diamides), were assessed for their efficiency in causing mortality to second instar S. frugiperda larvae at 24, 48 and 72 h post-treatment at five different serial concentrations (10 to 0.625 mg liter.sup.-1). The second instar S. frugiperda larvae were susceptible to the tested synthetic insecticides, however, the toxicity index of synthetic insecticides was estimated based on lethal concentration 50 (LC.sub.50 ), while, LC.sub.50 was calculated from the data of larval mortality. The broflanilide and abamectin proved to be the most toxic having the highest toxicity index of 100 and 78.29%, respectively, followed by cypermethrin and bifenthrin were showed toxicity index of 75.47 and 66.89%, respectively. The LC.sub.50 values were 0.606 and 0.774 mg liter.sup.-1 for broflanilide and abamectin, respectively, followed by cypermethrin and bifenthrin were showed LC.sub.50 values of 0.803 and 0.906 mg liter.sup.-1 at 72 h post-treatment. Rest of the other synthetic insecticides were showed moderate toxicity index of 42.11 to 62.09%, based on LC.sub.50 values were 1.439 to 0.976 mg liter.sup.-1 at 72 h post-treatment. The efficiency of synthetic insecticides was increased by increasing concentration level and exposure time. The screened synthetic insecticides among seven insecticides perhaps, provide basis for the development of novel insecticides for controlling S. frugiperda population after further research to evaluate and validate the laboratory results in the field.

The fall armyworm (Spodoptera frugiperda) is one of the most destructive pests of corn. New infestations have been reported in the East Hemisphere, reaching India, China, Malaysia, and Australia, causing severe destruction to corn and other crops. In Puerto Rico, practical resistance to different mode of action compounds has been reported in cornfields. In this study, we characterized the inheritance of resistance to chlorantraniliprole and flubendiamide and identified the possible cross-resistance to cyantraniliprole and cyclaniliprole. The Puerto Rican (PR) strain showed high levels of resistance to flubendiamide (RR.sub.50 = 2,762-fold) and chlorantraniliprole (RR.sub.50 = 96-fold). The inheritance of resistance showed an autosomal inheritance for chlorantraniliprole and an X-linked inheritance for flubendiamide. The trend of the dominance of resistance demonstrated an incompletely recessive trait for H1 ([male sign] SUS x [female sign] PR) x and an incompletely dominant trait for H2 ([female sign] SUS x [male sign] PR) x for flubendiamide and chlorantraniliprole. The PR strain showed no significant presence of detoxification enzymes (using synergists: PBO, DEF, DEM, and VER) to chlorantraniliprole; however, for flubendiamide the SR = 2.7 (DEM), SR = 3.2 (DEF) and SR = 7.6 (VER) indicated the role of esterases, glutathione S- transferases and ABC transporters in the metabolism of flubendiamide. The PR strain showed high and low cross-resistance to cyantraniliprole (74-fold) and cyclaniliprole (11-fold), respectively. Incomplete recessiveness might lead to the survival of heterozygous individuals when the decay of diamide residue occurs in plant tissues. These results highlight the importance of adopting diverse pest management strategies, including insecticide rotating to manage FAW populations in Puerto Rico and other continents.

The fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae), invaded China in 2019. The species has been established as a year-round breeding population in most of the southern provinces which are the main winter maize planting areas. The effect of rising nighttime temperatures, driven by the changing climate in this region, on the growth and development of S. frugiperda is unclear. Results of this study show that the survival rate of larvae and pupae significantly declined with daytime temperatures declining and the nighttime temperature range increasing. Development rate accelerated along with the increasing daytime temperatures and nighttime temperatures, except for the intermediate treatments (daytime temperature 24 °C and diurnal range from 2–6 °C). Predictions of FAW development and warnings to local farmers need to be adjusted to take into account more rapid development when nighttime temperatures increase in the warming climate. The Fall Armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae), is a serious migratory pest. After invading China in 2019, the species was established as a year-round breeding population in most of the southern provinces. The area of winter maize in this region has been increasing due to the huge demand of fresh maize consumption, which is potentially at risk from this invasive pest, although the growth and development of S. frugiperda in the region’s changing climate is unclear, particularly with rising temperatures at night. Here, we used the highest daytime temperatures of 27 °C, 24 °C, 20 °C and decreased these by 2, 4 and 6 °C to reflect the range of nighttime temperatures indicative of winter conditions in a warming climate to evaluate the effect of increasing night temperatures on the growth and development of S. frugiperda. Results show that the survival of larvae and pupae significantly declined with daytime temperatures declining and the nighttime temperature range increasing. Significant developmental effects were observed across all daytime–nighttime temperature treatments, except for adults. Additionally, there were significant interaction effects for all stages, except the egg stage, and generation time. The development rate increased with the increasing daytime temperatures and nighttime temperatures, except for the intermediate treatments (Group II). The uniformity of pupation and emergence times were higher under high daytime temperatures and nighttime temperature treatments. Predictions of FAW development and warnings to local farmers need to be adjusted to take into account the more rapid development when nighttime temperatures increase in the warming climate. These results will support decision makers in developing long-term management strategies for FAW in southern China.

Fall armyworm (Spodoptera frugiperda J. E. Smith), a serious pest of maize and other cereals, recently invaded the Old World potentially threatening the food security and incomes of millions of smallholder farmers. Being able to assess the impacts of a pest on yields is fundamental to developing Integrated Pest Management (IPM) approaches. Hence, working with an early maturing, medium maturing and late maturing variety, we inoculated maize plants with 2.sup.nd instar S. frugiperda larvae at V5, V8, V12, VT and R1 growth stages to investigate the effects of FAW induced damage on yield. Different plants were inoculated 0-3 times and larvae were removed after 1 or 2 weeks to generate a wide range of damage profiles. We scored plants for leaf damage at 3, 5 and 7 weeks after emergence (WAE) using the 9 point Davis scale. While at harvest we assessed ear damage (1-9 scale), and recorded plant height and grain yield per plant. We used Structural Equation Models to assess the direct effects of leaf damage on yield and indirect effects via plant height. For the early and medium maturing varieties leaf damage at 3 and 5 WAE, respectively, had significant negative linear effects on grain yield. In the late maturing variety, leaf damage at 7 WAE had an indirect effect on yield through a significant negative linear effect on plant height. However, despite the controlled screenhouse conditions, in all three varieties leaf damage explained less than 3% of the variation in yield at the plant level. Overall, these results indicate that S. frugiperda induced leaf damage has a slight but detectable impact on yield at a specific plant developmental stage, and our models will contribute to the development of decision-support tools for IPM. However, given the low average yields obtained by smallholders in sub-Saharan Africa and the relatively low levels of FAW induced leaf damage recorded in most areas, IPM strategies should focus on interventions aimed at improving plant vigour (e.g. through integrated soil fertility management) and the role of natural enemies, as these are likely to result in greater yield gains at lower cost than a focus on FAW control.

The fall armyworm, Spodoptera frugiperda, is one of the major destructive pests of agriculture in Pakistan. The widespread use of insecticides for the management of S. frugiperda has resulted in the field-evolved resistance to insecticides in different strains worldwide. However, field-evolved resistance to insecticides has not yet been reported in S. frugiperda from Pakistan. Following reports of control failure of S. frugiperda in Punjab, Pakistan, a study was planned to investigate resistance to insecticides from different classes in field strains of S. frugiperda to confirm whether the resistance was indeed evolving. Here, we explored resistance to spinetoram, emamectin benzoate, indoxacarb, diflubenzuron, methoxyfenozide, chlorpyrifos and cypermethrin in seven field strains and compared them with a laboratory susceptible reference (Lab-SF) strain of S. frugiperda. Compared with the Lab-SF strain at the LC.sub.50 levels, the field strains exhibited 24.8-142.7 (spinetoram), 33.4-91.4 (emamectin benzoate), 30.1-90.6 (indoxacarb), 16.1-38.4 (diflubenzuron), 18.4-51.8 (methoxyfenozide), 37.1-222.9 (chlorpyrifos), and 61.9-540.6 (cypermethrin) fold resistance ratios (RRs). In the presence of detoxification enzyme inhibitors [piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF)], the toxicity of all the insecticides, with the exception of spinetoram, was significantly enhanced in the tested field strains of S. frugiperda, providing insight into the metabolic mechanism of resistance. Additionally, compared with the Lab-SF strain, the resistant field strains exhibited elevated activities of detoxification enzymes such as glutathione S-transferases (GST), carboxylesterases (CarE) and mixed-function oxidases (MFO). Overall, the findings of the present study provide robust evidence of field-evolved resistance to insecticides in S. frugiperda, which needs to be managed to minimize yield losses of different crops caused by this global pest.

There is growing research interest in the fall armyworm (FAW) Spodoptera frugiperda, a polyphagous insect that is a major pest of maize crops worldwide. We investigated the relationship between planting date of maize and FAW infestation in South Kivu, eastern Democratic Republic of Congo, in two sampling seasons (September to October 2020 and February to March 2021). Five planting dates were considered for 45 fields in each season. The incidence, severity of attack and larval density of FAW were assessed at the 8-leaf stage (V8) of maize development in monoculture and intercropping systems. Planting period, classified as late or early, had a strong influence on FAW larval density, incidence and severity. The results showed that the late planting period (mainly on 30 October in season-1 and 30 March in season-2) had the highest larval density, incidence and severity of attack compared to the early planting period (15 September in season-1 and 01 Mars in season-2). During the season-1, five larval stages were found in the same field, whereas all larval stages were present in season-2, regardless of planting period. High densities of L4, L5 and L6 larvae were much more associated with late planting and incidence appeared to be highest when these larvae were present. The presence of L2 and L3 larval stages was observed in maize cropping systems intercropped with soybean and peanuts, while maize in monoculture and intercropped with cassava and beans was colonized by L4, L5 and L6 larvae. This study highlights the existence of different maize planting dates in South Kivu and demonstrates that late plantings have significant FAW infestations compared to early plantings. It provides a basis for developing climate-smart integrated pest management.

The fall armyworm (Spodoptera frugiperda) is a major economic pest in the United States and has recently become a significant concern in African and Asian countries. Due to its increased resistance to current management strategies, including pesticides and transgenic corn, alternative management techniques have become more necessary. Currently, silicon (Si) is being used in many pest control systems due to its ability to increase plant resistance to biotic and abiotic factors and promote plant growth. The current experiments were carried out at the College of Plant Protection, Gansu Agricultural University, Lanzhou, China, to test the effect of Si on lifetable parameters and lipase activity of fall armyworm and vegetative and physiological parameters of maize plants. Two sources of Si (silicon dioxide: SiO.sub.2 and potassium silicate: K.sub.2 SiO.sub.3) were applied on maize plants with two application methods (foliar application and soil drenching). The experiment results revealed that foliar applications of SiO.sub.2 and K.sub.2 SiO.sub.3 significantly (P[less than or equal to]0.05) increased mortality percentage and developmental period and decreased larval and pupal biomass of fall armyworm. Similarly, both Si sources significantly (P[less than or equal to]0.05) reduced lipase activity of larvae, and fecundity of adults, whereas prolonged longevity of adults. Among plant parameters, a significant increase in fresh and dry weight of shoot, stem length, chlorophyll content, and antioxidant activity was observed with foliar applications of Si. Root fresh and dry weight was significantly (P [less than or equal to] 0.05) higher in plants treated with soil drenching of SiO.sub.2 and K.sub.2 SiO.sub.3 . Moreover, SiO.sub.2 performed better for all parameters as compared to K.sub.2 SiO.sub.3 and control treatment. The study conclusively demonstrated a significant negative effect on various biological parameters of fall armyworm when plants were treated with Si, so it can be a promising strategy to control this pest.

The fall armyworm (FAW) is a pest that can cause severe damage to crops, particularly maize and cotton, resulting in agricultural losses. It has developed resistance to various types of insecticides due to certain gene mutations in its body. Our study aims to investigate how these genes affect the pest’s sensitivity to insecticides. We utilized amplicon sequencing to analyze 21 sites within six related genes and identified both known and unknown mutations. Subsequently, molecular docking simulations were employed to assess the impact of these mutations on the binding ability between insecticides and proteins. Our findings indicate that these mutations reduce the binding ability, potentially contributing to increased insecticide resistance. Thus, our study could unveil the variation and evolution of resistance genes in FAW. The fall armyworm (FAW), Spodoptera frugiperda, is a worldwide agricultural pest that invaded China in 2018, and has developed resistance to multiple insecticides. The evolution of insecticide resistance is facilitated by mutations of target genes responsible for conferring resistance. In this study, amplicon sequencing analyzed 21 sites in six resistance genes. In addition to known mutations, unknown variants were also found, including novel variants: F290C (ace-1 gene, 0.1% frequency), I1040T/V (CHSA gene, 0.1% frequency), A309T (GluCl gene, 0.1% frequency), and I4790T/V (RyR gene, 0.1% frequency). Additionally, molecular docking was employed to investigate the impact of the aforementioned new mutations on insecticide binding to proteins. The analyses indicated that the binding abilities were reduced, similar to the resistance mutations that were reported, implying these novel mutations may confer transitional resistance. This study may provide a foundation for understanding the functions of these novel mutations in the evolutionary processes that drive the emergence of insecticide resistance in this invasive species.

Fall armyworm (FAW; Spodoptera frugiperda), an exotic moth which recently invaded Africa, is a highly destructive pest of cereals especially maize a highly valued staple crop in Nigeria. The use of natural enemies such as predators or parasitoids for FAW control is more economically viable and environmentally safer than currently recommended synthetic insecticides. Natural enemies to combat the pest have not yet been reported in Nigeria. An exploration for the pests' natural enemies was undertaken by collecting FAW eggs and larvae from maize fields. These were reared in the laboratory for emergence, identification and efficacy as natural enemies. This yielded Euplectrus laphygmae (Hymenoptera: Eulophidae); Telenomus remus (Hymenoptera: Platygastridae) and Trombidium sp. (Acari.: Trombidiidae). Cotesia or Apanteles spp. were inferred to occur since Stictopisthus sp. (Hym.: Ichneumonidae), a secondary parasitoid, that attacks cocoons of Microgasterinae (e.g. Cotesia, Apanteles etc.) also emerged. Species of yet-to-be identified predators were also observed in various niches of maize plants. A positive relationship was found between FAW instar and the number of E. laphygmae eggs/instar ranging, on average, from 1.5 on second instar to 5.5 on fourth instars hosts. Parasitism rate of T. remus on FAW eggs was 100%. Parasitic mite infestation resulted in increasing paleness, reduced feeding, growth and movement as well as death of FAW 1.sup.st instars. Thus, the occurrence of FAW natural enemies in Nigeria calls for advocacy campaign to incorporate their use into integrated pest management strategies that attract and allow natural enemies to thrive for FAW management.