2nd Instars Research Articles

Bidirectional Predation Between Larvae of the Hoverfly Episyrphus balteatus (Diptera: Syrphidae) and the Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae).

The fall armyworm, Spodoptera frugiperda (J. E. Smith), a newly invasive pest, has natural insect enemies that hold promise as biological control agents. Here we analyzed predation rates between natural enemy insect, the syrphid Episyrphus balteatus (De Geer) and S. frugiperda in all paired combinations of all immature stages for each insect in petri dishes. The 2nd and 3rd instars E. balteatus larvae consumed 1st and 2nd instars S. frugiperda larvae, and 3rd and higher larval instars of S. frugiperda preyed on all instar larvae of E. balteatus. The 2nd and 3rd instars larvae of E. balteatus preyed on 1st and 2nd larval instars of S. frugiperda, consistent with the Holling type III response in petri dishes, with a theoretical maximum predation of 77 and 71 individuals in 24 h. The 5th and 6th instars S. frugiperda larvae consumed E. balteatus larvae, also with the Holling type III response, with a theoretical maximum predation on 1st instar E. balteatus larvae were 29 and 36 individuals, respectively. In a plant cage trial study, predation results were similar to those in petri dishes but with a lower predation number. None of the S. frugiperda larvae that fed on E. balteatus larvae developed to adulthood, and only about 20% of E. balteatus larvae that fed on S. frugiperda larvae became adults which had a significantly shorter lifespan than those who consume aphids. This two-way predation study revealed the complexity of S. frugiperda invasion and provided new insights into relationship between pests and natural enemies.

Efficacy of Helicoverpa Armigera Nucleopolyhedrovirus on Soybean for Control of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in Arkansas Agriculture.

Simple SummaryHelicoverpa zea is a major pest of soybean, and has developed resistance to many insecticides. This has led to an exploration of alternative control tactics. One such tactic is Helicoverpa armigera nucleopolyhedrovirus (HearNPV). Although using a biological agent as a control tactic has limitations, the purpose of this study was to address the effectiveness of HearNPV in controlling each H. zea larval instar by simulating a field application on soybean and observing mortality. Furthermore, this study addresses the potential for infection in one generation to lead to infection in a sequential generation. Our results indicate that HearNPV is effective at controlling 1st–3rd instar larvae, but does not effectively control 4th or 5th instar larvae. Also, a sequential generation of 2nd instar larvae succumbed to viral infection faster than the previous infestation. Therefore, HearNPV is capable of cross-generational infection, and could be a useful tool in producer’s management tactics for H. zea.Helicoverpa armigera nucleopolyhedrovirus (HearNPV) is a naturally occurring virus commercially produced for control of Heliothines, including Helicoverpa zea. One drawback with using this virus for control has been the slower time to mortality compared with synthetic insecticides. However, a new formulation (Heligen®) has anecdotally been thought to result in quicker mortality than previously observed. The objective of this study was to evaluate percent defoliation, the efficacy of HearNPV on mortality for each H. zea larval instar, and the potential for control of a second infestation. Fourteen days after the first infestation, all plants were re-infested with a second instar larva to simulate a second infestation. Helicoverpa armigera nucleopolyhedrovirus was effective at killing 1st–3rd instars, resulting in 99% mortality over 4–6 days. However, 4th and 5th instar mortality only reached 35%. Second infestation larvae died between 3.4 and 3.8 days, significantly faster than the 1st infestation of 2nd instars, which had a mean time to mortality of 4.9 days. An increase in mortality rate is probably due to increasing viral concentrations after viral replication within the first hosts. Final defoliation percentages were significantly smaller in the treated plants versus the untreated plants. Only 3rd and 4th instar larvae caused percent defoliation to exceed the current Arkansas action threshold of 40%. Helicoverpa armigera nucleopolyhedrovirus in the Heligen formulation can control 1st–3rd instars within 4–6 days, while keeping defoliation below the action threshold of 40%.

Inter - and intraspecific relationships between Macrosiphum rosae (Hemiptera: Aphididae) and Chrysoperla externa (Neuroptera: Chrysopidae)

The predator Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) is a polyphagous species that has, among its wide range of acceptable prey, the aphid Macrosiphum rosae (Linnaeus, 1758) (Hemiptera: Aphididae), an important pest of rose plants. We assessed the consumption of nymphs and adults of M. rosae by C. externa larvae, the predatory efficiency, and larval survival under different predator:prey ratios, densities of aphids, and ages of aphids. The bioassays were performed at 25 ± 1°C and 70 ± 10% RH under a 12-hour photoperiod, with aphids taken from roses of the cultivar Avalanche. Consumption was assessed by making young aphids (2nd and 3rd instars) and more developed aphids (4th instar and adult) available throughout the larval stage of the predator. The predatory efficiency and survival were studied for second-instar larvae offered M. rosae nymphs at densities of 20, 40, 80, 120, and 160 using predator:prey ratios of 1:5, 1:10, and 1:20. The assessments were performed 24, 48, and 72 hours after putting the species together. All of the C. externa instars consumed younger than older aphids. Larvae in the third instar consumed 80% of the young aphids and 77% of the older aphids. The higher the predator:prey ratio and larval density, the higher the predatory efficiency and the lower the larval survival. The ratios 1:5 and 1:10 led to the elimination of younger and older aphid populations 72 hours into the interaction between species.

Oviposition and development of the gregarious parasitoid Homalotylus eytelweinii (Hymenoptera: Encyrtidae) in relation to host stage of predaceous ladybirds

ABSTRACT Though predaceous ladybirds (Coleoptera: Coccinellidae) are known to be attacked by a wide array of parasitoids, the biology of these parasitoids remains largely unknown. This study was focused on the gregarious parasitoid Homalotylus eyteweinii that attacks multiple taxa of predaceous ladybirds, to understand how females allocate brood and their offspring develop in relation to host stage at parasitism with the seven-spot ladybird Coccinella septempunctata as the host. The parasitoid spent the same length of time on ovipositor insertion in response to different host instars. All instars of the host were equally susceptible to parasitism. Parasitism success from oviposition to adult emergence was greater for the 2nd instar than for late instars while similar between the 2nd and 1st instars. Both egg-to-host mummification time and egg-to-adulthood time were longer for the 1st instar than for the late instars. Realised brood size was smaller for the 1st instar host than for the late instars, and there were no differences among the late instars. Sex ratio of realised brood was not significantly different among host instars and was female-biased. Body size of offspring male and female adults at emergence was not significantly different among host instars. These results suggest that middle instars of C. septempunctata are of higher quality for offspring development of H. eytelweinii.

Prey instar preference and functional responses of Mallada basalis (Walker) (Neuroptera: Chrysopidae) to different life stages of Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

• The green lacewing Mallada basalis is a promising predator to the prey Phenacoccus solenopsis. • M. basalis larvae prefer early- over late-stage nymphs or adult P. solenopsis. • M. basalis exhibits a type II functional responses to P. solenopsis. • The 3rd instar M. basalis showed higher attack rate and shorter handling time than 2nd instar. Prey instar preference and functional responses of 2- and 3-instar Mallada basalis (Walker) (Neuroptera: Chrysopidae) larvae to 1- to 3-instar Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) nymphs and adults were assessed in laboratory. Results indicated that both 2- and 3-instar M. basalis larvae preferred young over old P. solenopsis nymphs and adults were the least preferred. The 3-instar M. basalis larvae preyed more adult P. solenopsis than 2-instar larvae. Mallada basalis exhibited type II functional responses to prey densities: An increase in prey density leads to an increase in consumed preys. Regardless of P. solenopsis stages, the number of preys consumed by the 3-instar M. basalis larvae was greater than that by the 2-instar larvae. Attack rates and handling times differed depending on prey and predator stage combinations. The highest attack rate (1.1874) and lowest handling time (0.0040 h) were observed for the 3-instar M. basalis larvae fed on the 1-instar P. solenopsis nymphs. Regardless of P. solenopsis stages, the attack rate of 3-instar M. basalis was greater than 2-instar, whereas the reverse held regarding handling time. The findings collectively indicated that 3-instar M. basalis larvae have greater potential than 2-instar as efficient biological control agent of P. solenopsis. In developing real world biological control programs, however, the 2-instar M. basalis may be released if necessary since the final efficacy of the predator is the summation of the 2- and 3-instar M. basalis .

Efficacy of Thai indigenous entomopathogenic nematodes for controlling fall armyworm (Spodoptera frugiperda)\xa0(J. E. Smith)(Lepidoptera; Noctuidae)

BackgroundUnder laboratory and greenhouse conditions, the virulence of 2 isolates of Thai indigenous entomopathogenic nematodes (EPNs) in controlling the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera; Noctuidae), was demonstrated. Six EPNs dosages were tested against 2 larval instars of FAW under the laboratory conditions, while 2 different concentrations were tested under the greenhouse conditions.ResultsThe results of a laboratory experiment revealed that 2 Thai indigenous EPNs isolates (Heterorhabditis indica isolate AUT 13.2 and Steinernema siamkayai isolate APL 12.3) were efficient against the FAW, 2nd and 5th larval instars. Six different nematode concentrations (50,100, 150, 200, 250 and 300 infectious juveniles (IJs) ml−1) were evaluated, and all were proven to be effective, with the mortality rate associated with concentration. Inoculated larvae in the 2nd instar was more vulnerable than that in the 5th instar. H. indica isolate AUT 13.2 was more destructive than S. siamkayai isolate APL 12.3. The greatest mortality rate of 2nd instar larvae was 83% when H. indica AUT 13.2 was applied at the concentration of 250 IJs ml−1, and 68% when the nematode S. siamkayai APL 12.3 was used at the concentration of 300 IJs ml−1. At 250 IJsml−1, the highest mortality rate of the 5th instar larvae was 45% for H. indica AUT 13.2 and 33% for S. siamkayai APL 12.3, respectively. To customize the concentration and volume of nematodes suspension evaluated in the greenhouse settings, the most sensitive stage of FAW and the optimum concentration that caused the highest mortality were used. The concentrations of both indigenous nematodes’ isolates were 20,000 and 50,000 IJsml−1 per pot, respectively, and the results showed that the mortality rates were lower than that in the laboratory. FAW mortality rate was the highest (58%) in case of the nematode H. indica isolate AUT 13.2, against (45%) in case of S. siamkayai isolate APL 12.3, at the 50,000 IJs ml−1 concentrations.ConclusionsThe study revealed the 2 Thai indigenous EPNs isolates (H. indica isolate AUT 13.2 and S. siamkayai isolate APL 12.3) were capable of controlling the FAW in both laboratory and greenhouse environments. The 2 Thai EPNs showed the potential to be considered as a biological control agent.

Insecticidal Activity of seed extracts of Annona squamosa L., against the cotton leafworm Spodoptera littoralis (Boisd.)

The apple sugar, Annona squamosa have been reported to have toxic and biological activities against various insect pests. Twelve natural chemical compounds were identified from A. squamosa seeds extract. Acetone and methanol extracts of A. squamosa seeds were laboratory prepared to investigate their toxicity and other biological effects against Spodoptera littoralis larvae. Toxicity of acetone and methanol seed extracts of A. squamosa against 2nd and 4th instar larvae of S. littoralis were tested at different w/v concentrations using the leaf dipping bioassay technique. The results showed that, the acetone extract was more effective against the 2nd instar larvae of S. littoralis, LC50 values were 1.9, 1.7 and 1.1%, compared with the methanol extract, LC50 values were 2.8, 2.4 and 1.6% on 8, 11 and 14 exposure days, respectively. Regarding the efficiency of both A. squamosa seeds extracts against the 4th instar larvae, the acetone extract was again more toxic than the methanol one. The LC50 values of the acetone extract were 2.9, 2.1, and 0.97%, while the LC50 values of the methanol extract were 3.2, 2.1 and 1.7% on 8, 11 and 14 exposure days, respectively. In addition, the data exhibited that, the treatment of the 2nd instars larvae of S. Littoralis with acetone seed extract of A. squamosa at LC25 and LC50 prolonged the larval and pupal duration and reduced the pupal weight. Malformations of pupae and adults were recorded.

Evaluation of Metarhizium rileyi Farlow (Samson) impregnated with azadirachtin and indoxacarb against Helicoverpa armigera (Hubner)

BackgroundEntomopathogenic fungi are the most versatile having a wide host range, capable of infecting insects at different developmental stages. In the present study, Metarhizium rileyi, at the concentrations of 102, 103, 104, 105, 106, 107 and 108 conidia/ml and sub-lethal concentrations of azadirachtin (1.02 and 1.53 ppm) and indoxacarb (0.72 ppm) were evaluated against the 1st, 2nd, 3rd, 4th and 5th larval instars of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) under laboratory conditions.ResultsM. rileyi applied at 106 conidia/ml caused a maximum mortality of 83.33 and 80.00% of 1st and 2nd larval instars of H. armigera, respectively. The maximum mortality of 3rd, 4th and 5th larval instars of H. armigera with 108 conidia/ml of M. rileyi was 83.33, 76.67 and 53.33%, respectively. When M. rileyi blended with azadirachtin at 1.02 ppm, the highest mortality rate of 86.21% at 106 conidia/ml against 2nd instar larvae was resulted. Similarly, M. rileyi applied at 108 conidia /ml mixed with azadirachtin (1.53 ppm) showed 89.66% mortality of 3rd instar larvae. The 2nd instar larvae treated with M. rileyi at 106 conidia/ml, mixed with indoxacarb (0.72 ppm), the corrected mortality rate was 82.14%. Concentration mortality response of 3rd instar larvae to M. rileyi blended with indoxacarb (0.72 ppm) was 85.71% at 108 conidia/ml. The median lethal concentration (LC50) values were 5.51 × 103, 1.86 × 104, 2.81 × 105 and 5.55 × 105 conidia/ml for 1st, 2nd, 3rd and 4th larval instars, respectively, after 7 days of treatment. M. rileyi when mixed with sub-lethal concentrations of azadirachtin (1.02 ppm) and indoxacarb (0.72 ppm) resulted LC50 values of 1.09 × 104 conidia/ml and 1.37 × 104 conidia/ml against 2nd instar larvae, respectively, after 24 hours. Similarly, M. rileyi mixed with sub-lethal concentrations of azadirachtin (1.53 ppm) and indoxacarb (0.72 ppm) resulted LC50 values of 3.12 × 108 and 3.06 × 105 conidia/ml against 3rd instar larvae, respectively, after 24 hours. The study revealed that the susceptibility of larvae decreased in case of large larval instars.ConclusionsM. rileyi can be utilized as one of the component of Integrated Pest Management Program for the eco-friendly management of H. armigera. As the application of M. rileyi @ 107 conidia/ml alone or in combination with azadirachtin (1.02 and 1.53 ppm) or indoxacarb (0.72 ppm) resulted to the highest mortality.

Effects of Aqueous Extracts of Endophyte-Infected Grass Achnatherum inebrians on Growth and Development of Pea Aphid Acyrthosiphon pisum.

Simple SummaryDrunken horse grass Achnatherum inebrians is a widely distributed perennial poisonous grass on the grasslands of Northern and Northwestern China. The present study focused on contact toxicity of aqueous extracts of endophyte-infected (E+) and endophyte-free (E−) plants of A. inebrians in different growth periods on pea aphids. These results show that extracts from endophyte-containing plants may contain compounds that may be used to control insects and lay a foundation for deeper chemical analysis to identify insecticidal compounds.The pea aphid Acyrthosiphon pisum has a worldwide distribution and causes serious losses for agricultural production. Drunken horse grass Achnatherum inebrians is a widely distributed perennial poisonous grass on the grasslands of Northern and Northwestern China. The present study focused on contact toxicity activity of aqueous extracts of endophyte-infected (E+) and endophyte-free (E−) A. inebrians in different growth periods of pea aphids, and the growth and development of two color morphs of F1 generation nymphs. Both of the color morphs had development durations in E+ treatments that tended to be longer at 1st, 2nd, 3rd, and 4th instars than E− and control (CK). The E+ treated aphids also showed decreased weights at maturity with over all lower mean relative growth rates (MRGR). Aphid survival of E+ treated aphids was lower than that of E− and CK at all growth periods. Seeding stage E+ extracts showed a greater propensity for negatively affecting aphids than did E+ extract at maturity and the yellowing stage. These results show that extracts from endophyte-containing plants may contain compounds that may be used to control insects.

Green Synthesis and Characterization of CuO@SiO2 Nanocomposite using Gum Arabic (Acacia senegalensis) (L) against Malaria Vectors

The nanocomposite CuO@SiO2 was synthesized through green pathway using Gum Arabic. The green synthesized nanocomposite was characterized using Scanning Electron Microscopy (SEM), Energy Diffraction X-Ray (EDX), Ultra-Violet/Visible spectroscopy, and Fourier Transform Infra-Red (FTIR). These techniques confirmed the formation of CuO@SiO2 nanocomposite. The toxicity studies were conducted for 24 h on 1st, 2nd, 3rd, and 4th instars of malaria vectors at various concentrations of 10, 20, and 25 Mg/L. The LC50 for the 1st, 2nd, 3rd, and 4th instars were found to be 7.525, 7.980, 8.026 and 9.741 Mg/L, respectively, whilst the LC90 for the 1st, 2nd, 3rd and 4th instars were found to be 14.839, 24.937, 57.77 and 48.5 Mg/L, respectively. The correlation coefficient values between concentrations and mortality for instars were obtained in the range of 0.944 - 0.984. These correlation coefficient values indicate that mortality rates increases with the increase in concentrations. The CuO@SiO2 nanocomposite could be a new nanolarvicide for malaria vector control in tropical countries. HIGHLIGHTS Nanocomposite was synthesized through green Sol gel method using gum Arabic and characterized by Scanning Electron Microscopy (SEM), Energy Diffraction X-Ray (EDX), Ultra-Violet/Visible spectroscopy, and Fourier Transform Infra-Red (FTIR) Larvicidal activity of nanocomposite against Anopheles gambiaecomplex was carried following World Health Organization protocol Probit analysis was conducted to evaluate lethal concentrations (LC50 and LC90) of the nanoparticles against the malaria vectors The CuO@SiO2 nanocomposites could be a potential nanolarvicide for larval source management of malaria vectors GRAPHICAL ABSTRACT

Endophytic fungi confirmed as entomopathogens of the new invasive pest, the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), infesting maize in South Sumatra, Indonesia

BackgroundThe fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), is a new invasive pest in Indonesia causing financial losses. S. frugiperda larvae hide in the leaf midrib all day. To overcome the hidden larvae, pathogenic endophytic fungi are needed. The objective of this research was to molecularly identify the endophytic fungal species from South Sumatra and determine the most pathogenic species against S. frugiperda larvae. Endophytic fungal identification was based on morphological and molecular characteristics. The molecular identification was based on gene sequential analysis of Intergenic Transcribed Spacer (ITS) 1 and ITS 4. Bioassay of the endophytic fungal species was treated against the 2nd larval instar of S. frugiperda.ResultThe results of molecular identification revealed endophytic fungal species consisted of Chaetomium sp. (GaTpeOi, JgTjPr, PiCrPga, and CaCjPga isolates), Aspergillus niger (L.) Van Tieghem (PsgTjPr, JgByU, and JaBuBys), Beauveria bassiana (Balsamo) Vuillemin (JgSPK, JaGiP, JaSpkPGA(2), JgCrJr, and JaTpOi (1) isolates), Curvularia lunata (Wakker) Boed. (JaGiPRB, CMTJP, JaMsBys, JaSpkPga(3), and JgTgSr isolates), Aspergillus flavus Link. (JgPWSR isolate), Penicillium citrinum Thom F 1539 (JaTpOi(2) isolate), and Metarhizium anisopliae (Metschn.) Sorokin (CaTpPGA isolate). All fungal isolates were deposited in the GenBank. The endophytic fungal species of B. bassiana (JgSPK isolate) caused up to (22.67%) mortality, C. lunata (JaSpkPga(3) isolate) caused (17.33%) mortality, and M. anisopliae (CaTpPga isolate) caused (8%) mortality of the pest’s larvae. First report of B. bassiana and C. lunata isolated from maize (Zea mays L.), while M. anisopliae was isolated from red chili (Capsicum annuum L.) as entomopathogenic endophytic fungi against S. frugiperda larvae in Indonesia.ConclusionThe endophytic fungi species of B. bassiana, C. lunata, and M. anisopliae had potentials as entomopathogens of S. frugiperda.

Larvicidal activity of different plant parts of Asparagus setaceus against dengue vector Aedes aegypti

Plant-based natural products are preferred over synthetic insecticides because natural products are eco-friendly and much less prone to the development of resistance. This has necessitated research for the development of the eco-friendly, biodegradable indigenous method for the control of vectors. Mosquito larvicidal efficacy of crude and ethanol extracts of the leaf, bark, root, and fruit of Asparagus setaceus (Asparagaceae) against Aedes aegypti was evaluated in the present study. Phytochemical screening of all the plant parts was also done. Crude and ethanol extracts of different parts of A. setaceus showed efficient larvicidal properties against Ae. aegypti in the following descending order fruit> root> bark> leaf. Fruit ethanolic extract exhibited the highest mortality (100%) against 1st and 2nd instars larvae at 24 hours of exposure. The result of the three-way factorial ANOVA of an ethanolic extract with different plant parts, different time intervals, and different instars revealed a significant difference in larval mortality (P

Elemental enrichment of the exoskeleton of the whip spider Phrynus marginemaculatus (Arachnida: Amblypygi)

Amblypygi is a small order of arachnids that includes the whip spiders. Like other members of the clade Pedipalpi, these arachnids are cryptic predators that use their antenniform appendages to detect prey, and spinose pedipalps for quick prey capture. To date, there is very little information on the composition of their exoskeleton despite its importance in predation and defense. Here, we performed the first analysis of a whip spider exoskeleton using energy-dispersive X-ray spectroscopy (SEM-EDS). Our studies of Phrynus marginemaculatus CL Koch, 1840 were designed to (1) determine if elemental profiles differ between instars and (2) determine if and how elemental profiles of whip spiders differ from other closely related arachnids. We found the whip spider exoskeleton to contain several trace metal elements including calcium, magnesium, manganese, potassium, sodium, and zinc. The diversity and abundance of trace elements is relatively low throughout the exoskeleton of 2nd instars but increases in adults. In particular, the chelicerae and pedipalps are well reinforced with several metal elements, most notably calcium and zinc, which are also present in the tarsal claws. A similar elemental distribution is known for adult whip scorpions (Thelyphonida). In P. marginemaculatus, these metal elements are similarly present in adult exuviae. The elemental enrichment of the whip spider exoskeleton is comparable to that present in other members of the Pedipalpi and Tetrapulmonata, reflecting a relatively conserved profile for the few species that have been examined.

Biology study of white grub Holotrichia nagpurensis (Scarabaeidae: Melolonthinae)

Biology of polyphagous insect pest Holotrichia nagpurensis was studies in laboratory during 2019-2020. H. nagpurensis beetles (all types mated, unmated, male and female) were collected by using Light traps (fitted with 6-8 watts mercury tube Light; ACTINIC BL, PHILIPS) placed nearby host Neem trees, Azadirachta indica, Guava, Psidium guajava, Bakayan, Melia azedarach, in evening time from 7:45 to 9: 45 pm in the moths of June-July from Noorpur village in Ghaziabad district of Uttar Pradesh, India (28.7444° N, 77.5526° E) and identified by National Bureau of Agricultural Insect Resources, Bengaluru, Indian Council of Agricultural Research. All collected beetles kept individually in 1 liter capacity containers with moist soil. The mated female laid eggs an average of 29.800±3.247 eggs singly at a depth of 5-10 cm in the moist soil. The incubation period of the eggs was 12.960±0.501 days. 1st instars lasted 17.660±0.510 days; subsequent 2nd and 3rd instars were lasted for 35.140±0.530 and 86.120±0.800 days, respectively. The pupal period was recorded about 25.860±0.515 days and adult longevity was observed 101.860±3.575 days. Total life cycle recorded 277.960±3.371 days with 59.840±4.676 % survival and 0.518±0.039, 3.548±0.080 and 0.368±0.026 larval growth index, pupal growth index and developmental index respectively. All grubs feed on live maize roots in controlled conditions up to pupation. The simple methodology for rearing of root grubs on live maize roots under laboratory conditions was attempted and life cycle of H. nagpurensis was studied successfully.

Assessment of combining biosynthesized silver nanoparticles using Bacillus thuringiensis and gamma irradiation for controlling Pectinophora gossypiella (saunders) (lepidoptera: Gelechiidae)

Purpose Combining gamma irradiation and nanotechnology has become one of the most promising new approaches for area-wide (AW) pest management in recent years. The laboratory trials were conducted to determine the combining effects of BT-AgNPs and gamma irradiation for controlling P. gossypiella. Radio-sensitivity of male pupae at different doses of gamma radiation and the effectiveness of biosynthesized silver nanoparticles using Bacillus thuringiensis on larval instar were assayed. Additionally, the ultrastructure changes on the alimentary canal of 4th instar larvae were studied to evaluate the impact of the combined approach at a cellular level. Materials and methods Laboratory- rearing technique was used for rearing Pectinophora gossypiella. The irradiation process was achieved at Co60 - Gamma Chamber (4000 A). Alanine dosimeters were used for measuring the average absorbed dose and dose mapping. Preparation of Silver nanoparticles (AgNPs) using Bacillus thuringiensis (Bt) and their characterization has been investigated. The treated 4th instar larvae by gamma irradiation or ∕and BT-AgNPs were dissected under the stereo microscope. The alimentary canal was obtained anatomically and Transmission Electron Microscope) was used in examining the stained sections. Results Based on the nonhatching eggs produced by irradiated males’ pupae, the values of effective doses were calculated. The effective doses ranged from 16 to 291 Gy for the ED25 - ED75. The sterility index reached 74.1% when irradiated with males by 291 Gy crossed with nonirradiated females and the adult emergence decreased to be 35.3%. The insecticidal potential of Bt-AgNPs on the 2nd and 4th larval instars was dose-dependent and its LC50 toxicity value was 0. 3 and 0. 4 mg/ml, respectively. The lethal concentration LC50 of the 2nd instar larvae increased the larval and pupal mortality to 55% and 44.4%, respectively, and reduced the adult emergence to be 55.6%. The combining effects of Bt-AgNPs with 291 Gy induced 100% pupae mortality and there was no adult emergence in F1 generation. Such effects also severed the ultrastructure deformity of the midgut of the 4th instar larvae after the two-day post-treatment. Conclusions The combining effects are recommended as an effective IPM program to control P. gossypiella by releasing sterile males (derived from pupae irradiated with 291 Gy) crossing with the normal females in the field, and reducing the fertility of the population to 31.2%. Subsequently, the resulted larvae treated with LC50 of Bt-AgNPs prevented the adult emergence and stopped the life cycle of P. gossypiella.

The Life Cycle of Armyworm, Spodoptera litura (Noctuidae: Lepidoptera) Destructive Pest of Cabbage

Armyworm, Spodoptera litura is a destructive pest of several agricultural and horticultural crops all over the world including Pakistan. The life cycle of S. litura was checked on cage leaves under laboratory conditions during 2019. The incubation period was completed in 2-4 days with an average of 3.12 + 0.39 days. The colour of neonate larvae, second, third, fourth, fifth and sixth instar was pale green, dark green, dark blue-green, dark blackish-brown and blackish brown, respectively. The average life period of 1st, 2nd, 3rd, 4th, 5th and 6th larval instar was 3.34 + 0.32, 2.57 + 0.45, 3.49 + 0.45, 3.11 + 0.67, 3.33 + 0.87 and 2.98 ± 0.33 days, respectively. The pre-pupal and pupal periods was lasted 2-3 and 6-11 days, respectively. The female was long-lived than male. The longevity of males was 6-10 days while the female was 9-12 days. The ovipositional, pre-ovipositional and post ovipositional period was lasted 7.67 + 1.40, 1.74 + 0.51 and 1.78 + 0.45 days, respectively. The study showed that cabbage is a suitable host for pest growth and development and larvae feed vigorously to cabbage leaves.

Efficacy of Ricinus communis L., Cassia occidentalis L. and Bacillus thuringiensis against Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Helicoverpaarmigera is one of the most destructive pests of field crops worldwide. The Study was designed to investigate through laboratory screening the insecticidal activity of Ricinus communis, Cassia occidentalis and Bacillus thuringiensis var. Kurstaki (Btk) and their combinations against 2nd larval instar of H. armigera. Five concentrations (4%, 6%, 8%, 10% and 12%) of each plant extract and (0.62, 1.25, 2.5, 5, and 10 mg/ml) of Bt were used in this experiment. Mortality (%) was recorded after 24,48,72 and 96 hrs post treatment. The results showed that R. communis, C. occidentalis and Btkhave insecticidal activity against 2nd instar larvae of H. armigera. The highest concentration (12%) caused 80% and 70% larval mortality after 96 hrs for R. communis and C. occidental respectively. The statistical analysis revealed that there is a significant differences between all treatments and control. Additionally, all combinations (plant/plant or plant/Bt) increased the mortality %. The results also clearly demonstrate that the R. communis are significantly more toxic than C. occidental where the LC50 values were 6.4 % for R. communis and 8.1% for C. occidental. On the other hand LC50 value for Bt was 0.41 mg/ml. The binary mixture of R. communis and C. occidental have a potentiation effect after 48 hrs. Regarding the mixture of Bt and plant extracts the results revealed that R. communis and Bt mixture induced a potentiation effect whereas C. occidental and Bt mixture induced a an additive effects.

On the virulence of the entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae (Ascomycota: Hypocreales), against the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae)

BackgroundThe diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a noxious pest of cruciferous crops all over the world causing serious economic damage. Management of insect pest generally depends on chemical control; however, due to development of resistance against all types of insecticides, alternative approaches especially utilization of a microbial agent is inevitable.ResultsPotential of 2 entomopathogenic fungi (EPF), viz., Beauveria bassiana and Metarhizium anisopliae, was evaluated against 2nd and 3rd larval instars of P. xylostella by adopting leaf dip and direct spraying methods under laboratory conditions. Significant mortality rate was achieved by each fungus under adopted methodologies. However, B. bassiana was found to be more effective in both conditions than M. anisopliae. Highest mean corrected mortality (77.80%) was recorded, when spores of B. bassiana were sprayed on the 2nd instar larvae (LC50=1.78×104/ml) after the 6th day of treatment. Similarly, incase of M. anisopliae LC50 for the 2nd instar at the same methodology was 2.78×104/ml with a mortality percentage of 70.0%. Offspring sex ratio was non-significantly related to treatment concentration and methodology, except for the control.ConclusionBeauveria bassiana and M. anisopliae had potential to suppress P. xylostella infestations when applied appropriately. Present findings suggested that B. bassiana and M. anisopliae when sprayed on immatures of host insect had more effect as compared to leaf dip procedure. Furthermore, no significant effect of concentrations was observed on sex ratio.

Evaluation of antixenosis in soybean against Spodoptera litura by dual-choice assay aided by a statistical analysis model: Discovery of a novel antixenosis in Peking.

The method for evaluating soybean (Glycine max) antixenosis against the common cutworm (Spodoptera litura) was developed based on a dual-choice assay aided by a statistical analysis model. This model was constructed from the results of a dual-choice assay in which Enrei, a soybean cultivar susceptible to S. litura, was used as both a standard and a test leaf disc for 2nd–5th instar larvae. The statistical criterion created by this model enabled the evaluation of the presence of antixenosis. This method was applied to four soybean varieties, including Tamahomare (susceptible), Himeshirazu (resistant), IAC100 (resistant), and Peking (unknown), as well as Enrei. Subsequently, the degrees of antixenosis were also compared by F-test, followed by maximum likelihood estimation (MLE). According to the results, the antixenosis of Tamahomare, Himeshirazu, and IAC100 was statistically reevaluated and Peking exhibited a novel antixenosis, which was stronger for 3rd–5th instar larvae than for 2nd instar.

Susceptibility of the Egyptian Cotton Leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) to Entomocidal Crystal Proteins Cry1Ac and Cry 2Ab Baseline Responses

The present study maybe is the first attempt in Egypt to evaluate the effect of Entomocidal proteins (Cry toxins) from Bacillus thuringiensis (Bt)Cry 1Ac and Cry 2Ab againstthe Egyptian cotton leafworm Spodoptera littoralis. The cotton leafworm one of the important Lepidopteran species is the most important pests in cotton fields. It can be controlled using Genetically Modified (GM) crops expressing insecticidal Bt proteins like Bt cotton and Bt corn. The long-term success of this technology demands pest resistance management. Important information for the successful management of resistance is the baseline susceptibility of the different target pests to the different Bt proteins. The data on baseline susceptibility should enable risk assessors and managers to assess whether GM cotton produces a Bt protein in a high-dose to specific target organisms and resistance has evolved during the commercial cultivation of this GM cotton event. During this study, the toxicity of Cry 1Ac and Cry 2Ab from the bacterium Bacillus thuringiensis to larvae of S. littoralis was assessed using first instar larvae with diet incorporation bioassays. Larvae reared (4 generations) from 2 populations of S. littoralis collected from major cotton-growing regions of Sohag and Assuit Governorates were tested. The LC50 for the Assuit strain was 140.11 and 88.54 µg/ml forCry 1Ac and Cry 2Ab, respectively. While, the LC50 for the Sohag strain was 410.75 and 37.62 µg/ml for Cry 1Ac and Cry 2Ab, respectively. On the other hand, the laboratory strain was more sensitive for the same Cry’s (Cry 1Ac and Cry 2Ab) the LC50 was13.40 and 0.23 µg/ml, respectively. The lethal concentration (LC50) against S. littoralis for 2nd and 4th instars larvae when using the B. thuringiensis as spores (commercial product) was 1.16 and 2.49 for 2nd and 4th instars, respectively. This study is very important as a preliminary step and baseline ahead of the commercial cultivation and production of Genetically Modified cotton (Bt cotton).