Interactions between Chelonus oculator and Se NPV in the biological control of Spodoptera exigua at different larval stages

Over the last few decades, important advances have been made in understanding of host–parasitoid relations and their applications to biological pest control. Not only has the number of agent species increased, but new manipulation techniques for natural enemies have also been empirically introduced, particularly in greenhouse crops. This makes biocontrol more complex, requiring a new mathematical modeling approach appropriate for the optimization of the release of agents. The present paper aimed at filling this gap by the development of a temperature- and stage-dependent dynamic mathematical model of the host–parasitoid system with an improved functional response. The model is appropriate not only for simulation analysis of the efficiency of biocontrol agents, but also for the application of optimal control methodology for the optimal timing of agent releases, and for the consideration of economic implications. Based on both laboratory and greenhouse trials, the model was validated and fitted to the data of Chelonus oculator (F.) (Hym.: Braconidae) as a biological control agent against the beet armyworm, Spodoptera exigua Hubner (Lep.: Noctuidae). We emphasize that this model can be easily adapted to other interacting species involved in biological or integrated pest control with either parasitoid or predator agents.

The beet armyworm (BAW), Spodoptera exigua (Lepidoptera: Noctuidae) is a highly destructive pest of vegetables and field crops. Management of beet armyworm primarily relies on synthetic pesticides, which is threatening the beneficial community and environment. Most importantly, the BAW developed resistance to synthetic pesticides with making it difficult to manage. Therefore, alternative and environment-friendly pest management tactics are urgently required. The use of pesticidal plant extracts provides an effective way for a sustainable pest management program. To evaluate the use of pesticidal plant extracts against BAW, we selected six plant species (Lantana camara, Aloe vera, Azadirachta indica, Cymbopogon citratus, Nicotiana tabacum , and Ocimum basilicum) for initial screening experiment. Four out of six plant species such as A. indica, N. tabacum, C. citratus and O. basilicum showed promising mortality of more than 50%. Therefore, we selected these four plant extracts for the subsequent experiments. Through contact bioassay, A. indica showed high mortality 66.63%, followed by the N. tabacum 53.33%, at 10% w/v concentration. Similarly, N. tabacum showed the highest mortality rate, 66% at 10% w/v concentration, followed by the A. indica 46% through feeding bioassay. Furthermore, the feeding deterrence assay showed that C. citratus had a high antifeedant index (−50) followed by A. indica (−39), and N. tabacum (−28). In living plant assay, the N. tabacum extract showed a low mean damage score 3.6 on living cotton plant followed by C. citratus 4.5 and A. indica 5.5. Hence, extracts of three plant species provided promising results against the BAW, which can minimize the use of synthetic chemicals, particularly for small landholding farmers. Further studies are also required to evaluate the effects of these plant extract against BAW on cotton plants under field conditions to optimize the further use.

Control of Grayak Caterpillar (Spodoptera exigua Hubn) pest by farmers generally is still use synthetic insecticides that have such a negative impact resistance, resurgence, killing natural enemies, increasing residue on crop yields, environmental pollution and health problems for users. One effort to reduce the use of chemical insecticides namely biological control method uses the Spodoptera exigua Nucleo Polyhedro Virus. This research was aimed to know the mortality rate army worm (Spodoptera exigua Hubn) by suspension Spodoptera exigua Nucleo Polyhedro Virus with different concentration. This research was conducted in the laboratory and green house of Vegetable Crops Research Institute at Lembang, Bandung from July until September 2014. This research used Randomized Completely Design (RCD). The result showed that Spodoptera exigua Nucleo Polyhedro Virus was significant to death of Spodoptera exigua. Spodoptera exigua Nucleo Polyhedro Virus concentration showed significant to mortality rates of Spodoptera exigua. In the test stage, the larvae of Spodoptera exigua 2 was the highest stage mortality was caused by infection Spodoptera exigua Nucleo Polyhedro Virus. Method of dipping caterpillars and feed applications were the best treatment because it showed the highest mortality. Pest control Grayak Caterpillar (Spodoptera exigua) in the field could use Spodoptera exigua Nucleo Polyhedro Virus coarse suspension of 10 g L-1 which was applied to the onion crop that was attacked. Keywords: Spodoptera exigua, Spodoptera exigua Nucleo Polyhedro Virus, Onion

Combined effects of three crystalline toxins from Bacillus thuringiensis with seven proteinase inhibitors on beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

The beet armyworm Spodoptera exigua Hübner, is an invasive pest of sugar beet and other field crops and vegetables. Here, the potential of sterile insect technique and inherited sterility to control of Spodoptera exigua have been investigated by pupae irradiation with Co60 gamma ray. The emerged adult’s reproduction, sterility, growth biology, sex ratio, mating competitiveness and inherited sterility in P1 and or F1 generations were investigated. Completely P1 sterile females and males were found when pupae were irradiated with 250 and 400 Gy, respectively. Female emergence was significantly reduced at 400 Gy, but their longevity increased with higher doses. When P1 male or female pupae were irradiated with 250 or 180 Gy respectively, the period of F1 larvae was longer than the normal. The emergence of F1 males decreased with increasing dose. When treated male parents were crossed with normal females, the sex ratio of F1 shifted in favor of males. F1 progeny showed more sterility than P1 generation and F1 males inherited more sterility than F1 females. Laboratory mating competitiveness indicated that 250 Gy irradiated males (IM) were competitive against untreated males (UM) in mating with untreated females (UF) even at 1:1:1 (IM:UM:UF) ratio.

Next generation biological control – an introduction

Quantitative studies of the relationships between infecting dose of Rous sarcoma virus, antiviral immune response, and tumor growth in chickens

Spodoptera exigua and Lyriomisa chinensis are one of the decstuctive insect and main obstacles in development of onion in Donggala. Pest control by chemicals has been widely reported to give a variety of negative impacts. Other efforts are needed as alternative technology to reduce impact of using synthetic chemical insecticides. One of them is entomopathogenic fungi as bio-insecticide. The objective of this research was to collect Beauveria spp. as enthomopathogen fungy. More specifically, number of Beauveria spp. was collected from several location and host as bio-insecticide formulation matter. There were 12 isolates of Beauveria spp. obtained from various locations in Central Sulawesi. Seven isolates from Lepidoptera while the remaining isolates were two from Homoptera, two from Hemiptera, and one from Coleoptera. Various insect species belong to Lepidoptera order investigated were Spodoptera exigua, Helicoperva armigera, Scirphopaga innotata, Ostrinia furnacalis and Plutella xylostella ; belong to Homoptera order were Nilaparvata lugens , and Aphids; belong to Hemiptera order were Leptocoryza acuta ; and belong to Coleoptera order was Oryctes rhinoceros . The observation indicated that the color of colony was ranged from yellowish white to white. There was no germination difference among the Beauveria spp. isolates in relationto to their location, host of insects, and insect orders. Differences in virulence showed only in Beauveria isolates from Spodoptera exigua with a high virulence against Spodoptera exigua pest and not for the other insects. Key Words : Beauveria bassiana , Bioinsecticide, Spodoptera exigua Hubn.

Insect parasitoids have been used for the biological control of insect pests through classical importations for the control of invasive phytophagous species, through seasonal or inundative releases for short-term suppression of indigenous or invasive pests, and through conservation of parasitoid activity by the provisioning of resource subsidies and alteration of management practices. In all cases, success in the suppression of a pest is dependent upon the behavioral decisions made by the parasitoid in searching for and parasitizing hosts. For example, in the case of classical biological control, patch choice decisions that maximize parasitoid fitness will tend to increase its regional impact, leading to greater suppression of the pest and success in biological control. In contrast, for augmentative biological control, the goal is to provide local pest suppression and behavior that maximizes fitness might, for example, lead parasitoids to abandon local patches of their hosts before the pest has been suppressed to the desired level. Thus, the behavioral ecology of insect parasitoids is central to the successful implementation of biological control programs. We explore how optimal foraging effects the suppression of global pest densities in a metapopulation context and to what extent the physiological condition and behavioral decisions of foraging parasitoids are likely to influence establishment and impact in classical biological control. In the case of inundative biological control, we discuss the trade-off between optimal foraging behavior and the level of pest suppression at a local scale and consider the use of chemical attractants and arrestants to increase parasitoid activity and patch time allocation. We also discuss the influence of host size and quality, and sex ratio (Wolbachia infection) on parasitoid mass rearing. Finally, the influence of nectar subsidies on parasitoid foraging behavior and host suppression is considered in the context of developing more efficient methods for conservation biological control. 1 Optimal foraging behavior and efficient biological control methods Nick J. Mills and Eric Wajnberg 4 N.J. MILLS AND E. WAJNBERG

White grubs are a major polyphagous pest that imposes damage upon several plant species, mostly by feeding their roots. White grub larvae are one of the hazardous pests found in sugarcane. This problem causes a substantial drop in sugarcane crop productivity every year in India. In this research, white grub larvae were subjected to biocontrol using developed formulations of Photorhabdus bacteria, symbiotically associated with entomopathogenic nematodes under laboratory conditions. The Photorhabdus bacteria isolated from entomopathogenic nematode- Heterorhabditis indica have insecticidal activity towards insect pests by exerting an array of toxic effects. The main insecticidal activity, i.e., chitinase enzyme production by these bacteria, was associated with mortality of insect pests. In the present investigation, chitinase production by Photorhabdus bacteria was determined by DEAE column chromatography. The various bacterial formulations of Photorhabdus were examined for their insecticidal activity against the white grub larvae under laboratory conditions. Mortality of the white grub larvae was observed after 24–48 hours of exposure. The formulations of Photorhabdus showed statistically significant effects on mortality of larvae. The percent mortality of larvae after treatment with formulation 3 was highly significant compared to those treated with formulation 1 and 2. Formulation 3 expressed a significantly lower LD50 value, i.e., 121.31 CFU/mL, over formulations 1 and 2, i.e., 127.34 & 133.56 CFU/mL, respectively. Formulation 3 showed greater efficacy in killing white grub larvae at lower concentrations. The formulation 3 of Photorhabdus bacteria has great potential to kill white grub larvae under laboratory conditions and requires further evaluation for its promising use as a biocontrol agent by pot and field studies.

Evaluation of five candidate receptors for three Bt toxins in the beet armyworm using CRISPR-mediated gene knockouts

Several aspects of the control of the beet armyworm, Spodopteraexigua (Hübner) (Lepidoptera: Noctuidae) in greenhouse crops with nuclear polyhedrosis viruses (NPVs) (Baculoviridae, subgroup A) were studied.Beet armyworm behaviour was observed in various crops. The distribution of egg batches (Chapter 2) was found to be similar in chrysanthemum, tomato, gerbera and geranium. Most eggs were laid on the underside of leaves within 10 cm of the soil surface. In chrysanthemum moths deposited more eggs on very young than on older plants. No correlation was found between size of egg batches and plant species, plant age or position within in a crop.After hatching beet armyworm larvae gradually moved upwards to the top of chrysanthemum plants (Chapter 3) and then predominantly fed on the upper foliage layers. On tomato, however, larvae did not move upwards and mainly fed on the lower leaves. On chrysanthemums most feeding of the younger larvae occurred at the underside of foliage while the upper epidermis remained intact. Larvae dispersing from a single egg batch of 35 eggs damaged about 90 small and 50 tall chrysanthemum plants during their development. The five successive larval stages contributed 0.1%, 0.4%, 4%, 20% and 75% to the total foliage consumption, respectively.Five nuclear polyhedrosis viruses infectious for beet armyworm larvae were compared for their potential as biological control agent (Chapter 4). Restriction endonuclease patterns of the DNA showed that three of the isolates, collected from deceased beet armyworm larvae in the Netherlands, are closely related with Mamestrabrassicae nuclear polyhedrosis virus (MbMNPV). Therefore they were named MbMNPV-NL80, MbMNPV-NL82 and MbMNPV-NL83. These isolates are not closely related with AutographcalifornicaMNPV (AcMNPV) and Spodopteraexigua MNPV (SeMNPV), both originating from the USA.Comparison of the biological activity of these five MNPVs (Chapter 4) showed that the SeMNPV has a greater biological activity against beet armyworm larvae than MbMNPV-NL80, - NL82, -NL83 and AcMNPV. The LD-50 values of the five MNPVs against second instar larvae were 3, 26, 14, 17 and 18 polyhedra, respectively. SeMNPV, therefore, seemed to be the most suitable candidate for biological control of the beet armyworm.Bioassays carried out with the droplet-feeding method showed that larvae became less susceptible to SeMNPV with increasing age (Chapter 5). The LD-50 values for the five subsequent larval instars were 4, 3, 39, 132 and 11610 polyhedra. The LT-50 values increased from ca. 3.5 days for first instars to almost 6 days for fifth instar larvae.Production of SeMNPV (Chapter 6) was carried out in late fourth instar larvae reared on semi- synthetic diet. A maximum amount of virus, 1 to 2 x 10 9polyhedra/larva, was produced in individually-reared larvae, after seven days of incubation at WC, with an inoculum of 7.5 x 10 4polyhedra/cm 2diet surface. Virus yield was reduced to ca. 9 x 10 8polyhedra/larva when production was carried out in groups of 400 and 600 larvae per container.Biological activity of virus harvested from living and from deceased larvae was similar. Microbial contaminants, predominantly bacteria, in the produced virus batches numbered 1-6% of the number of polyhedra. Vertebrate pathogens were not present in any of the produced virus batches.The effect of high-volume handspraying (HV), low-volume spinning disc (LV-SD) and ultra-low- volume electrodynamic (ULV-ED) application systems on the efficacy of larval control with SeMNPV was studied on chrysanthemum crops (Chapter 7). Virus applications with the LV-SD system generally showed a slightly better control efficacy than was achieved with the HV system. The efficacy of ULV-ED applications was much lower except on a very short crop, where control comparable with that of the LV-SD system was obtained.The efficacy of SeMNPV for control of beet armyworm larval populations was studied in chrysanthemum, gerbera, kalanchoe and tomato crops (Chapter 8). Applications of 1 x 10 8polyhedra/m 2resulted in 95-100% larval mortality on each of the crops. Virus applications caused comparable levels of mortality in populations of early and late instar larvae. Reduction in feeding damage to the crops, however, was more pronounced when the larvae were early instars at the time of virus application. Single applications with the virus resulted in higher levels of larval mortality as double applications with 0.1% methomyl or 0.1% diflubenzuron.In the general discussion (Chapter 9) the results from the various studies, commercial aspects and the current situation in Dutch greenhouse industry were evaluated. This lead to the final conclusion that there is good potential for the practical use and commercial development of SeMNPV as a control agent of beet armyworm larvae in Dutch greenhouses.

The compatibility of biological control agents with pesticides is a central concern in integrated pest management programs. The most common assessments of compatibility consist of simple comparisons of acute toxicity among pest species and select biocontrol agents. A more sophisticated approach, developed by the International Organisation of Biological Control (IOBC), is based on a tiered hierarchy made up of threshold values for mortality and sublethal effects that is used to determine the compatibility of pesticides and biological control agents. However, this method is unable to capture longer term population dynamics, which is often critical to the success of biological control and pest suppression. In this article, we used the delay in population growth index, a measure of population recovery, to investigate the potential impacts that the threshold values for levels of lethal and sublethal effects developed by the IOBC had on three biocontrol agents: sevenspotted lady beetle, Coccinella septempunctata L.; the aphid parasitoid Diaeretiella rapae (M'Intosh), and Fopius arisanus (Sonan), a parasitoid of tephritid flies. Based on life histories of these economically important natural enemies, we established a delay of 1-generation time interval as sufficient to disrupt biological control success. We found that delays equivalent to 1-generation time interval were caused by mortality as low as 50% or reductions of offspring as low as 58%, both values in line with thresholds developed by the IOBC. However, combinations of mortality and reduction of offspring lower than these values (from 32 to 43% each) over a simulated 4-mo period caused significant population delays. Furthermore, the species used in these simulations reacted differently to the same levels of effect. The parasitoid D. rapae was the most susceptible species, followed by F. arisanus and C. septempunctata. Our results indicate that it is not possible to generalize about potential long-term impacts of pesticides on biocontrol agents because susceptibility is influenced by differences in life history variables. Additionally, populations of biocontrol agents may undergo significant damage when mortality approaches 50% or when there is mortality of -30% and a 30% reduction in offspring caused by a sublethal effect. Our results suggest that more ecologically relevant measures of effect such as delays in population growth may advance our knowledge of pesticide impacts on populations of beneficial species.

The compatibility of biological control agents with pesticides is a central concern in integrated pest management programs. The most common assessments of compatibility consist of simple comparisons of acute toxicity among pest species and select biocontrol agents. A more sophisticated approach, developed by the International Organisation of Biological Control (IOBC), is based on a tiered hierarchy made up of threshold values for mortality and sublethal effects that is used to determine the compatibility of pesticides and biological control agents. However, this method is unable to capture longer term population dynamics, which is often critical to the success of biological control and pest suppression. In this article, we used the delay in population growth index, a measure of population recovery, to investigate the potential impacts that the threshold values for levels of lethal and sublethal effects developed by the IOBC had on three biocontrol agents: sevenspotted lady beetle, Coccinella septempunctata L.; the aphid parasitoid Diaeretiella rapae (M’Intosh), and Fopius arisanus (Sonan), a parasitoid of tephritid flies. Based on life histories of these economically important natural enemies, we established a delay of 1-generation time interval as sufficient to disrupt biological control success. We found that delays equivalent to 1-generation time interval were caused by mortality as low as 50% or reductions of offspring as low as 58%, both values in line with thresholds developed by the IOBC. However, combinations of mortality and reduction of offspring lower than these values (from 32 to 43% each) over a simulated 4-mo period caused significant population delays. Furthermore, the species used in these simulations reacted differently to the same levels of effect. The parasitoid D. rapae was the most susceptible species, followed by F. arisanus and C. septempunctata. Our results indicate that it is not possible to generalize about potential long-term impacts of pesticides on biocontrol agents because susceptibility is influenced by differences in life history variables. Additionally, populations of biocontrol agents may undergo significant damage when mortality approaches 50% or when there is mortality of ≈30% and a 30% reduction in offspring caused by a sublethal effect. Our results suggest that more ecologically relevant measures of effect such as delays in population growth may advance our knowledge of pesticide impacts on populations of beneficial species.

Viral infections of the central nervous system (CNS) are a major cause of morbidity largely due to lack of prevention and inadequate treatments. While mortality from viral CNS infections is significant, nearly two thirds of the patients survive. Thus, it is important to understand how the human CNS can successfully control virus infection and recover. Since it is not possible to study the human CNS throughout the course of viral infection at the cellular level, here we analyzed a non-lethal viral infection in the CNS of nonhuman primates (NHPs). We inoculated NHPs intracerebrally with a high dose of La Crosse virus (LACV), a bunyavirus that can infect neurons and cause encephalitis primarily in children, but with a very low (≤ 1%) mortality rate. To profile the CNS response to LACV infection, we used an integrative approach that was based on comprehensive analyses of (i) spatiotemporal dynamics of virus replication, (ii) identification of types of infected neurons, (iii) spatiotemporal transcriptomics, and (iv) morphological and functional changes in CNS intrinsic and extrinsic cells. We identified the location, timing, and functional repertoire of optimal transcriptional and translational regulation of the primate CNS in response to virus infection of neurons. These CNS responses involved a well-coordinated spatiotemporal interplay between astrocytes, lymphocytes, microglia, and CNS-border macrophages. Our findings suggest a multifaceted program governing an optimal CNS response to virus infection with specific events coordinated in space and time. This allowed the CNS to successfully control the infection by rapidly clearing the virus from infected neurons, mitigate damage to neurophysiology, activate and terminate immune responses in a timely manner, resolve inflammation, restore homeostasis, and initiate tissue repair. An increased understanding of these processes may provide new therapeutic opportunities to improve outcomes of viral CNS diseases in humans.