Insects

13 pages, 551 KiB

Open AccessArticle

A Comparison of the Vertical Transmission of High- and Low-Virulence Nucleopolyhedrovirus Strains in Lymantria Dispar L.

by Yuriy B. Akhanaev, Irina A. Belousova, Darya A. Lebedeva, Sergey V. Pavlushin and Vyacheslav V. Martemyanov

Insects 2020, 11(7), 455; https://doi.org/10.3390/insects11070455 - 20 Jul 2020

Cited by 8 | Viewed by 2635

Abstract

Baculoviruses can persist in insect host organisms after infection and may be vertically transmitted to the next generation, in which they may be reactivated. The goal of the present study was to compare the efficiency of the vertical transmission of high- and low-virulence [...] Read more.

Baculoviruses can persist in insect host organisms after infection and may be vertically transmitted to the next generation, in which they may be reactivated. The goal of the present study was to compare the efficiency of the vertical transmission of high- and low-virulence strains and the subsequent reactivation of Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) in the offspring of Lymantria dispar L. adults who survived after viral infection. As a result of parental infection, the fecundity of survived females, pupae weight, and fertility were significantly different compared to the untreated insects. However, differences in these parameters between high- and low-virulence strains were not observed. The prevalence of virus strains in the offspring measured by quantitative polymerase chain reaction also did not differ. When the larvae reached the fourth instar, they were starved to activate the vertically transmitted virus. The frequency of virus activation in the experiment was not dependent on the virulence of the virus strains. These results are helpful for understanding the strategy of virus survival in nature and for the selection of the most effective strains with transgenerational effects in the years following pest treatment. Full article

(This article belongs to the Special Issue Biological Control and Insect Pathology)

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14 pages, 2294 KiB

Open AccessArticle

Ecological Niche Modeling to Calculate Ideal Sites to Introduce a Natural Enemy: The Case of Apanteles opuntiarum (Hymenoptera: Braconidae) to Control Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America

by Nidia Bélgica Pérez-De la O, Saúl Espinosa-Zaragoza, Víctor López-Martínez, Stephen D. Hight and Laura Varone

Insects 2020, 11(7), 454; https://doi.org/10.3390/insects11070454 - 19 Jul 2020

Cited by 6 | Viewed by 4837

Abstract

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America where it threatens Opuntia native populations. The insect is expanding its distribution along the United States Gulf Coast. In the search for alternative strategies to reduce its impact, [...] Read more.

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America where it threatens Opuntia native populations. The insect is expanding its distribution along the United States Gulf Coast. In the search for alternative strategies to reduce its impact, the introduction of a natural enemy, Apanteles opuntiarum Martínez and Berta (Hymenoptera: Braconidae), is being pursued as a biological control option. To identify promising areas to intentionally introduce A. opuntiarum for the control of C. cactorum, we estimated the overlap of fundamental ecological niches of the two species to predict their common geographic distributions using the BAM diagram. Models were based on native distributional data for both species, 19 bioclimatic variables, and the Maxent algorithm to calculate the environmental suitability of both species in North America. The environmental suitability of C. cactorum in North America was projected from Florida to Texas (United States) along the Gulf coastal areas, reaching Mexico in northern regions. Apanteles opuntiarum environmental suitability showed a substantial similarity with the calculations for C. cactorum in the United States. Intentional introductions of A. opuntiarum in the actual distribution areas of the cactus moth are predicted to be successful; A. opuntiarum will find its host in an environment conducive to its survival and dispersal. Full article

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12 pages, 1153 KiB

Open AccessArticle

Propolis Envelope Promotes Beneficial Bacteria in the Honey Bee (Apis mellifera) Mouthpart Microbiome

by Hollie Dalenberg, Patrick Maes, Brendon Mott, Kirk E. Anderson and Marla Spivak

Insects 2020, 11(7), 453; https://doi.org/10.3390/insects11070453 - 18 Jul 2020

Cited by 22 | Viewed by 5847

Abstract

Honey bees collect and apply plant resins to the interior of their nest cavity, in order to form a layer around the nest cavity called a propolis envelope. Propolis displays antimicrobial activity against honey bee pathogens, but the effect of propolis on the [...] Read more.

Honey bees collect and apply plant resins to the interior of their nest cavity, in order to form a layer around the nest cavity called a propolis envelope. Propolis displays antimicrobial activity against honey bee pathogens, but the effect of propolis on the honey bee microbiome is unknown. Honey bees do not intentionally consume propolis, but they do manipulate propolis with their mouthparts. Because honey bee mouthparts are used for collecting and storing nectar and pollen, grooming and trophallaxis between adults, feeding larvae, and cleaning the colony, they are an important interface between the bees’ external and internal environments and serve as a transmission route for core gut bacteria and pathogens alike. We hypothesized that the antimicrobial activity of an experimentally applied propolis envelope would influence the bacterial diversity and abundance of the worker mouthpart microbiome. The results revealed that the mouthparts of worker bees in colonies with a propolis envelope exhibited a significantly lower bacterial diversity and significantly higher bacterial abundance compared to the mouthparts of bees in colonies without a propolis envelope. Based on the taxonomic results, the propolis envelope appeared to reduce pathogenic or opportunistic microbes and promote the proliferation of putatively beneficial microbes on the honey bee mouthparts, thus reinforcing the core microbiome of the mouthpart niche. Full article

(This article belongs to the Collection Bees and Their Symbionts)

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19 pages, 6598 KiB

Open AccessArticle

The Geometry and Mechanics of Insect Wing Deformations in Flight: A Modelling Approach

by Robin Wootton

Insects 2020, 11(7), 446; https://doi.org/10.3390/insects11070446 - 17 Jul 2020

Cited by 26 | Viewed by 7144

Abstract

The nature, occurrence, morphological basis and functions of insect wing deformation in flight are reviewed. The importance of relief in supporting the wing is stressed, and three types are recognized, namely corrugation, an M-shaped section and camber, all of which need to be [...] Read more.

The nature, occurrence, morphological basis and functions of insect wing deformation in flight are reviewed. The importance of relief in supporting the wing is stressed, and three types are recognized, namely corrugation, an M-shaped section and camber, all of which need to be overcome if wings are to bend usefully in the morphological upstroke. How this is achieved, and how bending, torsion and change in profile are mechanically interrelated, are explored by means of simple physical models which reflect situations that are visible in high speed photographs and films. The shapes of lines of transverse flexion are shown to reflect the timing and roles of bending, and their orientation is shown to determine the extent of the torsional component of the deformation process. Some configurations prove to allow two stable conditions, others to be monostable. The possibility of active remote control of wing rigidity by the thoracic musculature is considered, but the extent of this remains uncertain. Full article

(This article belongs to the Special Issue Insects: Functional Morphology, Biomechanics and Biomimetics)

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17 pages, 1490 KiB

Open AccessArticle

Attributes of Yellow Traps Affecting Attraction of Diaphorina citri (Hemiptera: Liviidae)

by Sandra A. Allan, Justin George, Lukasz L. Stelinski and Stephen L. Lapointe

Insects 2020, 11(7), 452; https://doi.org/10.3390/insects11070452 - 16 Jul 2020

Cited by 11 | Viewed by 3396

Abstract

Laboratory assays were conducted to evaluate responses of Diaphorina citri to various aspects of visual cues associated with traps in an effort to improve trap effectiveness. Addition of white or UV violet but not yellow light-emitting diodes (LEDs) increased attraction to standard yellow [...] Read more.

Laboratory assays were conducted to evaluate responses of Diaphorina citri to various aspects of visual cues associated with traps in an effort to improve trap effectiveness. Addition of white or UV violet but not yellow light-emitting diodes (LEDs) increased attraction to standard yellow adhesive traps moderately (11–17%), with no difference in attraction between white or UV violet LEDs. Addition of a black border on yellow traps enhanced collections. However, there were no differences between attraction to black patterns on traps. Comparisons were made between different commercial paints, some with UV-reflecting properties or fluorescence. A yellow paint with UV reflectance, used for painting bird decoys (decoy yellow), was more attractive than the standard yellow Olson sticky trap. Addition of white or green pigment to increase intensity or enhance green reflectance, respectively, did not increase attraction. Alteration of reflectance of Olson traps with addition of UV-reflecting or fluorescent pigments did not enhance attraction of D. citri. In field comparisons, decoy yellow and fluorescent yellow sticky traps were more attractive to D. citri than Olson yellow. Full article

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12 pages, 2432 KiB

Open AccessArticle

Molecular Identification and Geometric Morphometric Analysis of Haematobosca aberrans (Diptera: Muscidae)

by Tanasak Changbunjong, Jiraporn Ruangsittichai, Gerard Duvallet and Adrian C. Pont

Insects 2020, 11(7), 451; https://doi.org/10.3390/insects11070451 - 16 Jul 2020

Cited by 8 | Viewed by 3528

Abstract

The genus Haematobosca Bezzi, 1907 (Diptera: Muscidae) contains haematophagous flies of veterinary importance. A new fly species of this genus was recognised from northern Thailand based on morphological characters and described as Haematobosca aberrans Pont, Duvallet & Changbunjong, 2020. In the present study, [...] Read more.

The genus Haematobosca Bezzi, 1907 (Diptera: Muscidae) contains haematophagous flies of veterinary importance. A new fly species of this genus was recognised from northern Thailand based on morphological characters and described as Haematobosca aberrans Pont, Duvallet & Changbunjong, 2020. In the present study, the mitochondrial cytochrome c oxidase I (COI) gene was used to confirm the morphological identification of H. aberrans. In addition, landmark-based geometric morphometrics was used to determine sexual dimorphism. The molecular analysis was conducted with 10 COI sequences. The results showed that all sequences were 100% identical. The sequence was not highly similar to reference sequences from GenBank and did not match any identified species from Barcode of Life Data Systems (BOLD). Phylogenetic analysis clearly differentiated this species from other species within the subfamily Stomoxyinae. For geometric morphometric analysis, a total of 16 wing pictures were analysed using the landmark-based approach. The results showed significant differences in wing shape between males and females, with a cross-validated classification score of 100%. The allometric analysis showed that wing shape has no correlation with size. Therefore, the COI gene is effective in species identification of H. aberrans, and geometric morphometrics is also effective in determining sexual dimorphism. Full article

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12 pages, 2192 KiB

Open AccessArticle

Blood Meal Sources of Anopheles spp. in Malaria Endemic Areas of Honduras

by Denis Escobar, Krisnaya Ascencio, Andrés Ortiz, Adalid Palma, Ana Sánchez and Gustavo Fontecha

Insects 2020, 11(7), 450; https://doi.org/10.3390/insects11070450 - 16 Jul 2020

Cited by 10 | Viewed by 3343

Abstract

Malaria remains a life-threatening disease in many tropical countries. Honduras has successfully reduced malaria transmission as different control methods have been applied, focusing mainly on indoor mosquitoes. The selective pressure exerted by the use of insecticides inside the households could modify the feeding [...] Read more.

Malaria remains a life-threatening disease in many tropical countries. Honduras has successfully reduced malaria transmission as different control methods have been applied, focusing mainly on indoor mosquitoes. The selective pressure exerted by the use of insecticides inside the households could modify the feeding behavior of the mosquitoes, forcing them to search for available animal hosts outside the houses. These animal hosts in the peridomicile could consequently become an important factor in maintaining vector populations in endemic areas. Herein, we investigated the blood meal sources and Plasmodium spp. infection on anophelines collected outdoors in endemic areas of Honduras. Individual PCR reactions with species-specific primers were used to detect five feeding sources on 181 visibly engorged mosquitoes. In addition, a subset of these mosquitoes was chosen for pathogen analysis by a nested PCR approach. Most mosquitoes fed on multiple hosts (2 to 4), and 24.9% of mosquitoes had fed on a single host, animal or human. Chicken and bovine were the most frequent blood meal sources (29.5% and 27.5%, respectively). The average human blood index (HBI) was 22.1%. None of the mosquitoes were found to be infected with Plasmodium spp. Our results show the opportunistic and zoophilic behavior of Anopheles mosquitoes in Honduras. Full article

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9 pages, 1999 KiB

Open AccessCommunication

Low Mismatch Rate between Double-Stranded RNA and Target mRNA Does Not Affect RNA Interference Efficiency in Colorado Potato Beetle

by Wanwan He, Wenbo Xu, Kaiyun Fu, Wenchao Guo and Jiang Zhang

Insects 2020, 11(7), 449; https://doi.org/10.3390/insects11070449 - 16 Jul 2020

Cited by 8 | Viewed by 2541

Abstract

RNA interference (RNAi)-based technology has been proven as a novel approach for insect pest control. However, whether insects could evolve resistance to RNAi and the underlying mechanism is largely unknown. The target gene mutations were thought to be one of the potential ways [...] Read more.

RNA interference (RNAi)-based technology has been proven as a novel approach for insect pest control. However, whether insects could evolve resistance to RNAi and the underlying mechanism is largely unknown. The target gene mutations were thought to be one of the potential ways to develop the resistance. Here we predicted the effective siRNA candidates that could be derived from dsRNA against the Colorado potato beetle (CPB) β-Actin gene (dsACT). By site-directed mutagenesis, we synthesized the dsRNAs with the defect in generation of effective siRNAs (and thus were supposed to have comparable low RNAi efficacy). We showed that, with mismatches to the target gene, all the dsRNA variants caused similar levels of silencing of target gene, mortality and larval growth retardation of CPB. Our results suggest that when the mismatch rate of dsACT and target β-Actin mRNA is less than 3%, the RNAi efficiency is not impaired in CPB, which might imply the low possibility of RNAi resistance evolving through the sequence mismatches between dsRNA and the target gene. Full article

(This article belongs to the Special Issue Insecticide Resistance: The Genetic Basis and Underlying Mechanisms in Potato Pests)

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15 pages, 1183 KiB

Open AccessArticle

Agricultural-Grade Apple Cider Vinegar Is Remarkably Attractive to Drosophila suzukii (Diptera: Drosophiliadae) in Mexico

by Rodrigo Lasa, Saide Aguas-Lanzagorta and Trevor Williams

Insects 2020, 11(7), 448; https://doi.org/10.3390/insects11070448 - 15 Jul 2020

Cited by 10 | Viewed by 6835

Abstract

Due to its availability and low cost, apple cider vinegar (ACV) is a frequently used as an attractant for monitoring the invasive spotted wing drosophila, Drosophila suzukii. In laboratory cage experiments, the attraction of ACV alone was compared with ACV in mixtures [...] Read more.

Due to its availability and low cost, apple cider vinegar (ACV) is a frequently used as an attractant for monitoring the invasive spotted wing drosophila, Drosophila suzukii. In laboratory cage experiments, the attraction of ACV alone was compared with ACV in mixtures with different concentrations of acetic acid, propionic acid, different hydrolyzed proteins, synthetic fruit flavors (strawberry, blackberry and apple) and the addition of fruit nectars (grape, pineapple and apple). The addition of 5% apple nectar to ACV significantly increased fly captures, whereas other combinations were similar to or less attractive than ACV alone. Apple flavored vinegar was not attractive to flies. Captures did not vary significantly among the brands of ACV commonly sold in Mexico, except for one poorly-performing brand, but cup traps baited with an agricultural-grade ACV unfit for human consumption captured approximately two-fold more flies than the commercial attractants Suzukii Trap, Suzukii Trap Max Captures or ACV alone in cage experiments. Field trials performed in polytunnels planted with raspberry crops in Mexico resulted in two-fold to ten-fold higher numbers of D. suzukii captured by the agricultural-grade ACV compared to Droskidrink (a mixture of ACV, red wine and sugar), Suzukii Trap, Suzukii Trap Max Captures or edible grade ACV alone. The species selectivity of the agricultural grade ACV was similar to that of other attractants tested. Agricultural-grade ACV also captured higher numbers of female than male flies in field trials. We conclude that the remarkably high attractiveness and low cost of agricultural-grade ACV makes it a useful tool for monitoring D. suzukii populations in berry crops. Full article

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14 pages, 2410 KiB

Open AccessReview

High Voltage Electric Fields Have Potential to Create New Physical Pest Control Systems

by Shin-ichi Kusakari, Kiyotsugu Okada, Manabu Shibao and Hideyoshi Toyoda

Insects 2020, 11(7), 447; https://doi.org/10.3390/insects11070447 - 15 Jul 2020

Cited by 16 | Viewed by 10282

Abstract

An electric field is the space surrounding an electric charge, within which it is capable of exerting a perceptible force on another electric charge. Especially under high voltage, electric fields induce various electrostatic phenomena, some of which could be utilized to provide remarkable [...] Read more.

An electric field is the space surrounding an electric charge, within which it is capable of exerting a perceptible force on another electric charge. Especially under high voltage, electric fields induce various electrostatic phenomena, some of which could be utilized to provide remarkable pest control measures. The main focus of the present study was to introduce an attractive force generated by a surface charge on an insulated electrified conductor, which was successfully used to construct an electric field screen that prevented airborne nuisances (spores, flying insects, pollen, and fine smoke) from entering the interiors of various facilities. Another focus was the disinclination of insects to enter the electric field, thus, giving the electric field screen the ability to repel insects. Charges accumulated on the surfaces of non-insulated conductors are mobile through discharge, based on their potential difference. Such arc discharge was strong enough to destroy insects that were exposed to it. Some precedent illustrative examples are cited to explain the principles of attraction, dielectrophoretic movement of spores, and discharge-mediated positive electrification of insects, and to discuss how electric fields are generated and used in electric field-based pest control strategies. Full article

(This article belongs to the Special Issue Insect Physical Control: Electric Field-Based Pest Management Approach)

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14 pages, 1046 KiB

Open AccessArticle

Influence of Cover Crop Termination on Ground Dwelling Arthropods in Organic Vegetable Systems

by Laura Depalo, Giovanni Burgio, Serena Magagnoli, Daniele Sommaggio, Francesco Montemurro, Stefano Canali and Antonio Masetti

Insects 2020, 11(7), 445; https://doi.org/10.3390/insects11070445 - 15 Jul 2020

Cited by 9 | Viewed by 2926

Abstract

A key aspect in cover crop management is termination before the cash crop is planted. The aim of this study was to assess the effects of termination methods on ground-dwelling arthropods. The conventional mechanical termination method—i.e., green manuring by means of a disc [...] Read more.

A key aspect in cover crop management is termination before the cash crop is planted. The aim of this study was to assess the effects of termination methods on ground-dwelling arthropods. The conventional mechanical termination method—i.e., green manuring by means of a disc harrow—was compared to flattening using a roller crimper. Two different crop systems were investigated for two growing seasons; cauliflower was grown in autumn after the termination of a mixture of cowpea, pearl millet, and radish, and tomato was cropped in spring and summer after the termination of a mixture of barley and vetch. Ground beetles (Coleoptera: Carabidae), rove beetles (Coleoptera: Staphylinidae), and spiders (Araneae) were sampled by means of standard pitfall traps throughout the growing season of both cash crops. The roller crimper increased the overall abundance of ground beetles in the first growing season of both cash crops, whereas in the second year, no significant effect could be detected. Rove beetles were more abundant in plots where the cover crops were terminated by the roller crimper. Finally, green manuring increased the abundance of spiders, especially on the first sampling date after cover crop termination. Albeit different taxa showed different responses, the termination of cover crops by a roller crimper generally increased the abundance of ground dwelling arthropods. Given that most of the sampled species were generalist predators, their increased abundance could possibly improve biological control. Full article

(This article belongs to the Special Issue Conservation Biological Control in IPM and Organic Systems)

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17 pages, 1520 KiB

Open AccessArticle

Prophylactic Avoidance of Hazardous Prey by the Ant Host Myrmica rubra

by Hugo Pereira and Claire Detrain

Insects 2020, 11(7), 444; https://doi.org/10.3390/insects11070444 - 14 Jul 2020

Cited by 4 | Viewed by 2388

Abstract

Ants are the hosts of many microorganisms, including pathogens that are incidentally brought inside the nest by foragers. This is particularly true for scavenging species, which collect hazardous food such as dead insects. Foragers limit sanitary risks by not retrieving highly infectious prey [...] Read more.

Ants are the hosts of many microorganisms, including pathogens that are incidentally brought inside the nest by foragers. This is particularly true for scavenging species, which collect hazardous food such as dead insects. Foragers limit sanitary risks by not retrieving highly infectious prey releasing entomopathogenic fungal spores. This study investigates whether similar prophylactic strategies are also developed for food associated with weak or delayed risks of fungal contamination. We compared, in Myrmica rubra ant colonies, the retrieval dynamics of dead flies that were (1) conidia-free, (2) covered with a low amount of Metarhizium brunneum entomopathogenic conidia or (3) recently fungus-killed but not yet sporulating. Foragers mostly avoided fungus-killed prey and delayed the retrieval of conidia-covered flies. A second sanitary filter occurred inside the nest through a careful inspection of the retrieved prey. Ultimately, ants mostly consumed conidia-free and conidia-covered flies, but they relocated and discarded all fungus-killed prey outside of the nest. Our study confirms that, as a host of generalist entomopathogenic fungi, Myrmica rubra ants have developed a prophylactic avoidance and a differential management of prey depending on their infectious potential. We discuss the functional value as well as the possible cues underlying pathogen avoidance and prey discrimination in ants. Full article

(This article belongs to the Special Issue Ants as Partners and Hosts)

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11 pages, 354 KiB

Open AccessArticle

Evaluation of a Non-Chemical Compared to a Non-Chemical Plus Silica Gel Approach to Bed Bug Management

by Salehe Abbar, Changlu Wang and Richard Cooper

Insects 2020, 11(7), 443; https://doi.org/10.3390/insects11070443 - 14 Jul 2020

Cited by 7 | Viewed by 3124

Abstract

Bed bug resistance to commonly used pesticide sprays has led to exploring new pesticides and other strategies for bed bug management. Non-chemical methods are effective in bed bug management; however, they do not provide residual protection. Compared to insecticide sprays, dust formulations are [...] Read more.

Bed bug resistance to commonly used pesticide sprays has led to exploring new pesticides and other strategies for bed bug management. Non-chemical methods are effective in bed bug management; however, they do not provide residual protection. Compared to insecticide sprays, dust formulations are considered to provide longer residual control. We evaluated two bed bug management programs in apartment buildings. A building-wide inspection was initially conducted to identify bed bug infested apartments. Selected apartments were divided into two treatment groups: non-chemical plus silica gel dust treatment (10 apartments) and non-chemical treatment (11 apartments). After initial treatment, apartments were re-visited monthly for up to 6 months. During each visit, the total bed bug count per apartment was obtained by examining interceptor traps placed in the apartments and conducting a visual inspection. Mean bed bug count was reduced by 99% and 89% in non-chemical plus silica gel dust and non-chemical treatment, respectively. Non-chemical plus silica gel dust treatment caused significantly higher bed bug count reduction than the non-chemical treatment at 6 months. Bed bugs were eradicated from 40% and 36% of apartments treated with non-chemical plus silica gel dust treatment and non-chemical treatment, respectively. Full article

(This article belongs to the Special Issue Biology and Management of Bed Bugs)

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15 pages, 3183 KiB

Open AccessArticle

Distribution and Habitat Preferences of the Newly Rediscovered Telmatogeton magellanicus (Jacobs, 1900) (Diptera: Chironomidae) on Navarino Island, Chile

by Felipe Lorenz Simões, Tamara Contador-Mejías, Javier Rendoll-Cárcamo, Carolina Pérez-Troncoso, Scott A. L. Hayward, Edgar Turner and Peter Convey

Insects 2020, 11(7), 442; https://doi.org/10.3390/insects11070442 - 14 Jul 2020

Cited by 3 | Viewed by 2983

Abstract

The habitat of the intertidal flightless midge Telmatogeton magellanicus (Jacobs, 1900) is described for the first time from the northern coast of Navarino Island, Tierra del Fuego, Chile. Additionally, we report the first observations of adult behaviour in the wild. We delineate the [...] Read more.

The habitat of the intertidal flightless midge Telmatogeton magellanicus (Jacobs, 1900) is described for the first time from the northern coast of Navarino Island, Tierra del Fuego, Chile. Additionally, we report the first observations of adult behaviour in the wild. We delineate the species’ distribution across three tidal zones (high, mid and low), and identify substrate characteristics that favour the presence of the midge. The mid-tide zone was the key habitat utilized by T. magellanicus, with lower densities in the low-tide zone and no presence in the high-tide zone. There was a strong association between the presence of larvae and filamentous algae, especially Bostrychia spp. and, to a lesser extent, Ulva spp., as well as between larvae and the presence of larger, more stable boulders. As a result, the species’ overall distribution was widespread but patchy. We suggest that the main limiting factor is the relative humidity experienced in different habitats. One of the most striking features of the behavioural observations during data collection was the extremely active adults, which suggests high energy expenditure over a very short period of time. This may be due to the limited time available to find mates in a single low-tide period, when adults have about three hours after emerging from the pupa to complete mating and oviposition before inundation by the tide. The data presented here provide a baseline for future studies on this species’ ecology, phenology, physiology and general biology. Full article

(This article belongs to the Special Issue Polar Entomology)

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14 pages, 8789 KiB

Open AccessArticle

Genetic Diversity in Invasive Populations of Argentine Stem Weevil Associated with Adaptation to Biocontrol

by Thomas W. R. Harrop, Marissa F. Le Lec, Ruy Jauregui, Shannon E. Taylor, Sarah N. Inwood, Tracey van Stijn, Hannah Henry, John Skelly, Siva Ganesh, Rachael L. Ashby, Jeanne M. E. Jacobs, Stephen L. Goldson and Peter K. Dearden

Insects 2020, 11(7), 441; https://doi.org/10.3390/insects11070441 - 14 Jul 2020

Cited by 10 | Viewed by 3494

Abstract

Modified, agricultural landscapes are susceptible to damage by insect pests. Biological control of pests is typically successful once a control agent has established, but this depends on the agent’s capacity to co-evolve with the host. Theoretical studies have shown that different levels of [...] Read more.

Modified, agricultural landscapes are susceptible to damage by insect pests. Biological control of pests is typically successful once a control agent has established, but this depends on the agent’s capacity to co-evolve with the host. Theoretical studies have shown that different levels of genetic variation between the host and the control agent will lead to rapid evolution of resistance in the host. Although this has been reported in one instance, the underlying genetics have not been studied. To address this, we measured the genetic variation in New Zealand populations of the pasture pest, Argentine stem weevil (Listronotus bonariensis), which is controlled with declining effectiveness by a parasitoid wasp, Microctonus hyperodae. We constructed a draft reference genome of the weevil, collected samples from a geographical survey of 10 sites around New Zealand, and genotyped them using a modified genotyping-by-sequencing approach. New Zealand populations of Argentine stem weevil have high levels of heterozygosity and low population structure, consistent with a large effective population size and frequent gene flow. This implies that Argentine stem weevils were able to evolve more rapidly than their biocontrol agent, which reproduces asexually. These findings show that monitoring genetic diversity in biocontrol agents and their targets is critical for long-term success of biological control. Full article

(This article belongs to the Special Issue Population Genetics of Insects)

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10 pages, 1875 KiB

Open AccessArticle

Oral Ingestion of Bacterially Expressed dsRNA Can Silence Genes and Cause Mortality in a Highly Invasive, Tree-Killing Pest, the Emerald Ash Borer

by Ramya Shanivarsanthe Leelesh and Lynne K. Rieske

Insects 2020, 11(7), 440; https://doi.org/10.3390/insects11070440 - 14 Jul 2020

Cited by 21 | Viewed by 3631

Abstract

RNA interference (RNAi) is a naturally occurring process inhibiting gene expression, and recent advances in our understanding of the mechanism have allowed its development as a tool against insect pests. A major challenge for deployment in the field is the development of convenient [...] Read more.

RNA interference (RNAi) is a naturally occurring process inhibiting gene expression, and recent advances in our understanding of the mechanism have allowed its development as a tool against insect pests. A major challenge for deployment in the field is the development of convenient and efficient methods for production of double stranded RNA (dsRNA). We assessed the potential for deploying bacterially produced dsRNA as a bio-pesticide against an invasive forest pest, the emerald ash borer (EAB). EAB feeds on the cambial tissue of ash trees (Fraxinus spp.), causing rapid death. EAB has killed millions of trees in North America since its discovery in 2002, prompting the need for innovative management strategies. In our study, bacterial expression and synthesis of dsRNA were performed with E. coli strain HT115 using the L4440 expression vector. EAB-specific dsRNAs (shi and hsp) over-expressed in E. coli were toxic to neonate EAB after oral administration, successfully triggering gene silencing and subsequent mortality; however, a non-specific dsRNA control was not included. Our results suggest that ingestion of transformed E. coli expressing dsRNAs can induce an RNAi response in EAB. To our knowledge, this is the first example of an effective RNAi response induced by feeding dsRNA-expressing bacteria in a forest pest. Full article

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13 pages, 1975 KiB

Open AccessArticle

Impact of Sacbrood Virus on Larval Microbiome of Apis mellifera and Apis cerana

by Rujipas Yongsawas, Veeranan Chaimanee, Jeffery S. Pettis, Humberto Freire Boncristiani Junior, Dawn Lopez, Ammarin In-on, Panuwan Chantawannakul and Terd Disayathanoowat

Insects 2020, 11(7), 439; https://doi.org/10.3390/insects11070439 - 13 Jul 2020

Cited by 6 | Viewed by 3645

Abstract

In this study, we examined the impact of Sacbrood virus (SBV), the cause of larval honeybee (Apis mellifera) death, producing a liquefied a larva sac, on the gut bacterial communities on two larval honeybee species, Apis mellifera and Apis cerana. [...] Read more.

In this study, we examined the impact of Sacbrood virus (SBV), the cause of larval honeybee (Apis mellifera) death, producing a liquefied a larva sac, on the gut bacterial communities on two larval honeybee species, Apis mellifera and Apis cerana. SBV was added into a worker jelly food mixture and bee larvae were grafted into each of the treatment groups for 24 h before DNA/RNA extraction. Confirmation of SBV infection was achieved using quantitative reverse transcription polymerase chain reaction (RT-qPCR) and visual symptomology. The 16S rDNA was sequenced by Illumina sequencing. The results showed the larvae were infected with SBV. The gut communities of infected A. cerana larvae exhibited a dramatic change compared with A. mellifera. In A. mellifera larvae, the Illumina sequencing revealed the proportion of Gilliamella, Snodgrassella and Fructobacillus was not significantly different, whereas in A. cerana, Gilliamella was significantly decreased (from 35.54% to 2.96%), however, with significant increase in Snodgrassella and Fructobacillus. The possibility of cross-infection should be further investigated. Full article

(This article belongs to the Collection Bees and Their Symbionts)

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15 pages, 1297 KiB

Open AccessArticle

A Survey of Neotropiella Handschin, 1942 (Collembola, Neanuridae, Pseudachorutinae) with the Description of a New Brazilian Species

by Bruno C. Bellini, Wanda M. Weiner, Gabriel C. Queiroz and Raiane V. Paz

Insects 2020, 11(7), 438; https://doi.org/10.3390/insects11070438 - 13 Jul 2020

Cited by 1 | Viewed by 2091

Abstract

Neotropiella Handschin, 1942 is a pantropical genus of Pseudachorutinae with 18 species, 16 of which are from the Neotropical Region and 13 from Brazil. The genus has several species with unclear descriptions. Herein, we describe a new species of Neotropiella, survey the [...] Read more.

Neotropiella Handschin, 1942 is a pantropical genus of Pseudachorutinae with 18 species, 16 of which are from the Neotropical Region and 13 from Brazil. The genus has several species with unclear descriptions. Herein, we describe a new species of Neotropiella, survey the genus based on published papers and discuss its morphology, providing an updated genus diagnosis plus a detailed comparison table and a key to all known species. Neotropiella arretada sp. nov. is unique in the combination of a postantennal organ with 14–20 vesicles, its mandible with five teeth, its maxilla apically pointed and its unguis with a pair of reduced teeth. Widely distributed taxa may be species complexes, especially due to their unclear descriptions. Full article

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6 pages, 1278 KiB

Open AccessCommunication

Efficacy of a Novel Metaldehyde Application Method to Control the Brown Garden Snail, Cornu aspersum (Helicidae), in South Africa

by Annika Pieterse, Antoinette Paula Malan and Jenna Louise Ross

Insects 2020, 11(7), 437; https://doi.org/10.3390/insects11070437 - 13 Jul 2020

Cited by 3 | Viewed by 3672

Abstract

Baitchain is a novel molluscicide system that consists of metaldehyde pellets arranged on a cord and is designed to be tied around the base of tree trunks and act as a physical and chemical control method for molluscs. In this study, Baitchain is [...] Read more.

Baitchain is a novel molluscicide system that consists of metaldehyde pellets arranged on a cord and is designed to be tied around the base of tree trunks and act as a physical and chemical control method for molluscs. In this study, Baitchain is tested in a South African apple orchard and compared with traditional metaldehyde pellets (Sluggit) applied to the soil surface to determine the efficacy of the products against the brown garden snail, Cornu aspersum (Helicidae). The products were applied at two different concentrations, including 15 g/kg (Baitchain 15 and Sluggit 15) and 40 g/kg (Baitchain 40 and Sluggit 40) metaldehyde, and the products were either applied on their own, or in combination. Both treatments at 40 g/kg metaldehyde caused significant snail mortality when applied either on their own or in combination. However, significant mortality was also achieved by Baitchain 15 when applied on its own as well as in combination with Sluggit 15. The increased efficacy achieved by using Baitchain, even at the lower concentration, indicates that this novel method offers a viable physical and chemical control option for molluscs and could be incorporated as part of an integrated pest management strategy in South Africa, as well as other parts of the world. Full article

(This article belongs to the Special Issue Biology and Management of Slug and Snail Pests)

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15 pages, 1869 KiB

Open AccessArticle

Enzymatic Defense Response of Apple Aphid Aphis pomi to Increased Temperature

by Jan Dampc, Monika Kula-Maximenko, Mateusz Molon and Roma Durak

Insects 2020, 11(7), 436; https://doi.org/10.3390/insects11070436 - 11 Jul 2020

Cited by 21 | Viewed by 4086

Abstract

Climate change, and in particular the increase in temperature we are currently observing, can affect herbivorous insects. Aphids, as poikilothermic organisms, are directly exposed to temperature increases that influence their metabolism. Heat stress causes disturbances between the generations and the neutralization of reactive [...] Read more.

Climate change, and in particular the increase in temperature we are currently observing, can affect herbivorous insects. Aphids, as poikilothermic organisms, are directly exposed to temperature increases that influence their metabolism. Heat stress causes disturbances between the generations and the neutralization of reactive oxygen species (ROS). The aim of this work is focused on explaining how the aphid, using the example of Aphis pomi, responds to abiotic stress caused by temperature increase. The experiment was carried out under controlled conditions at three temperatures: 20, 25, and 28 °C. In the first stage, changes in the activity of enzymatic markers (superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), β-glucosidase, polyphenol oxidase (PPO), and peroxidase (POD)) were determined in aphid tissues, at each temperature. In the second stage, microcalorimetry monitored changes in heat emitted by aphids, at each temperature. Our results showed that A. pomi defense responses varied depending on temperature and were highest at 28 °C. The flexible activity of enzymes and increase in the metabolic rate played the role of adaptive mechanisms and ran more effectively at higher temperatures. The A. pomi thus protected itself against ROS excessive induction and the aphids were able to respond quickly to environmental stress. Full article

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16 pages, 2010 KiB

Open AccessArticle

Does the Infectious Status of Aphids Influence Their Preference Towards Healthy, Virus-Infected and Endophytically Colonized Plants?

by Junior Corneille Fingu-Mabola, Clément Martin, Thomas Bawin, François Jean Verheggen and Frédéric Francis

Insects 2020, 11(7), 435; https://doi.org/10.3390/insects11070435 - 11 Jul 2020

Cited by 10 | Viewed by 3435

Abstract

Aphids (Hemiptera: Aphididae) cause significant damage and transmit viruses to various crop plants. We aimed to evaluate how the infectious status of aphids influences their interaction with potential hosts. Two aphid (Myzus persicae and Rhopalosiphum padi) and plant (Nicotiana tabacum [...] Read more.

Aphids (Hemiptera: Aphididae) cause significant damage and transmit viruses to various crop plants. We aimed to evaluate how the infectious status of aphids influences their interaction with potential hosts. Two aphid (Myzus persicae and Rhopalosiphum padi) and plant (Nicotiana tabacum and Triticum aestivum) species were used. The preferences of aphids towards healthy, virus-infected (Potato Leafroll Virus (PLRV) and Barley Yellow Dwarf virus (BYDV)), and endophytic entomopathogenic fungi (EEPF)-inoculated (Beauveria bassiana and Metarhizium acridum) plants were investigated in dual-choice tests. The headspace volatiles of the different plant modalities were also sampled and analyzed. Viruliferous and non-viruliferous aphids were more attracted to EEPF-inoculated plants compared to uninoculated plants. However, viruliferous aphids were more attracted to EEPF-inoculated plants compared to virus-infected plants, while non-viruliferous insects exhibited no preference. Fungal-inoculated plants released higher amounts of aldehydes (i.e., heptanal, octanal, nonanal and decanal) compared to other plants, which might explain why viruliferous and non-viruliferous aphids were more abundant in EEPF-inoculated plants. Our study provides an interesting research perspective on how EEPF are involved in behavior of virus vector, depending on the infectious status of the latter. Full article

(This article belongs to the Special Issue Plant-Arthropod-Microorganism Interactions)

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15 pages, 2512 KiB

Open AccessArticle

Host Plant Species of Bemisia tabaci Affect Orientational Behavior of the Ladybeetle Serangium japonicum and Their Implication for the Biological Control Strategy of Whiteflies

by Mi Tian, Lili Xu, Jun Jiang, Shize Zhang, Tongxian Liu and Yongyu Xu

Insects 2020, 11(7), 434; https://doi.org/10.3390/insects11070434 - 11 Jul 2020

Cited by 6 | Viewed by 2226

Abstract

Serangium japonicum Chapin (Coleoptera: Coccinellidae) is a predominant predator with a preference for Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). To date, the orientational behavior of S. japonicum toward B. tabaci-infested plants has seldom been reported. In this study, greenhouse cage experiments and bioassays [...] Read more.

Serangium japonicum Chapin (Coleoptera: Coccinellidae) is a predominant predator with a preference for Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). To date, the orientational behavior of S. japonicum toward B. tabaci-infested plants has seldom been reported. In this study, greenhouse cage experiments and bioassays with wind tunnels, a Y-tube olfactometer and B. tabaci-induced plant volatiles were executed to clarify this behavior. In greenhouse cage experiments, B. tabaci adults significantly preferred eggplant, cucumber and tobacco to cotton and tomato, whereas S. japonicum adults preferred B. tabaci-infested eggplant, cucumber and cotton to tobacco and tomato. In wind tunnel bioassays, B. tabaci showed a clear preference for eggplant, cucumber and tobacco. Compared with B. tabaci-infested eggplant, cucumber or cotton, B. tabaci-infested tobacco was rarely visited by S. japonicum. In Y-tube bioassays, S. japonicum did not distinguish between B. tabaci-infested and uninfested eggplant. Nine common plant volatiles were detected in different plant species, suggesting that these volatiles may play an important role in the process by which S. japonicum looks for prey. In light of the current results, we discuss the implications of our findings and put forward to a new strategy—i.e., an eggplant + B. tabaci + S. japonicum system—to control B. tabaci damage in the integrated management of whitefly. Full article

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8 pages, 1176 KiB

Open AccessBrief Report

Body Size Differences between Foraging and Intranidal Workers of the Monomorphic Ant Lasius niger

by Mateusz Okrutniak, Bartosz Rom, Filip Turza and Irena M. Grześ

Insects 2020, 11(7), 433; https://doi.org/10.3390/insects11070433 - 10 Jul 2020

Cited by 10 | Viewed by 5528

Abstract

The association between the division of labour and worker body size of ants is typical for species that maintain physical castes. Some studies showed that this phenomenon can be also observed in the absence of distinct morphological subcastes among workers. However, the general [...] Read more.

The association between the division of labour and worker body size of ants is typical for species that maintain physical castes. Some studies showed that this phenomenon can be also observed in the absence of distinct morphological subcastes among workers. However, the general and consistent patterns in the size-based division of labour in monomorphic ants are largely unidentified. In this study, we performed a field experiment to investigate the link between worker body size and the division of labour of the ant Lasius niger (Linnaeus, 1758), which displays limited worker size variation. We demonstrated that the body size of workers exploring tuna baits is slightly but significantly smaller than the size of workers located in the upper parts of the nest. Comparing the present results with existing studies, large workers do not seem to be dedicated to work outside the nest. We suggest that monomorphic workers of certain body sizes are flexible in the choice of task they perform, and food type may be the important determinant of this choice. Full article

(This article belongs to the Special Issue Behavior and Ecology of Social Insects)

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16 pages, 1002 KiB

Open AccessArticle

Evaluation of the Physiological Host Range for the Parasitoid Ooencyrtus mirus, a Potential Biocontrol Agent of Bagrada hilaris

by Nancy Power, Fatemeh Ganjisaffar and Thomas M. Perring

Insects 2020, 11(7), 432; https://doi.org/10.3390/insects11070432 - 10 Jul 2020

Cited by 10 | Viewed by 2130

Abstract

The thelytokous egg parasitoid Ooencyrtus mirus Triapitsyn and Power (Hymenoptera: Encyrtidae) was recovered from brassica plant debris in Pakistan in an effort to find a biological control agent of the invasive bug Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) in North America. As the first [...] Read more.

The thelytokous egg parasitoid Ooencyrtus mirus Triapitsyn and Power (Hymenoptera: Encyrtidae) was recovered from brassica plant debris in Pakistan in an effort to find a biological control agent of the invasive bug Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) in North America. As the first step in determining the overall host range of this parasitoid, adult females were exposed to the eggs of eight alternate pentatomid host species, two non-pentatomid heteropterans, and two lepidopterans, in choice and no-choice tests. Although O. mirus was more successful on B. hilaris than the other species in terms of the number of the eggs laid, the number of emerged progeny, and the developmental time of the progeny, it was able to reproduce on all of the alternate hosts except for one of the lepidopterans, whose eggs appeared too small for this parasitoid. The results show O. mirus to be a generalist parasitoid species with a preference for B. hilaris. The results also indicate that there is a linear relationship between the mean body length of O. mirus females and the mean host egg weight with an adjusted

R^{2}

of 0.90. The implications of this study on the release of O. mirus for the control of B. hilaris are discussed. Full article

(This article belongs to the Special Issue Improving Invasive Insect Species Management)

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10 pages, 257 KiB

Open AccessArticle

Comparative Toxicity of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) to Selected Insecticides

by Fernando R. da Silva, Dario Trujillo, Oderlei Bernardi, Jose Carlos Verle Rodrigues, Woodward D. Bailey, Todd M. Gilligan and Daniel Carrillo

Insects 2020, 11(7), 431; https://doi.org/10.3390/insects11070431 - 10 Jul 2020

Cited by 19 | Viewed by 3745

Abstract

Until recently, the Old World bollworm (OWB) Helicoverpa armigera (Hübner) and the corn earworm Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) were geographically isolated. Both species are major pests of agricultural commodities that are known to develop insecticide resistance, and they now coexist in areas [...] Read more.

Until recently, the Old World bollworm (OWB) Helicoverpa armigera (Hübner) and the corn earworm Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) were geographically isolated. Both species are major pests of agricultural commodities that are known to develop insecticide resistance, and they now coexist in areas where H. armigera invaded the Americas. This is the first study to compare the susceptibility of the two species to conventional insecticides. The susceptibility of third instar H. armigera and H. zea larvae to indoxacarb, methomyl, spinetoram, and spinosad was determined using a diet-overlay bioassay in a quarantine laboratory in Puerto Rico. Mortality was assessed at 48 h after exposure for up to eight concentrations per insecticide. Spinetoram exhibited the highest acute toxicity against H. armigera, with a median lethal concentration (LC₅₀) of 0.11 µg a.i./cm², followed by indoxacarb and spinosad (0.17 µg a.i./cm² for both) and methomyl (0.32 µg a.i./cm²). Spinetoram was also the most toxic to H. zea (LC₅₀ of 0.08 µg a.i./cm²), followed by spinosad (0.17 µg a.i./cm²) and methomyl (0.18 µg a.i./cm²). Indoxacarb was the least toxic to H. zea, with an LC₅₀ of 0.21 µg a.i./cm². These findings could serve as a comparative reference for monitoring the susceptibility of H. armigera and H. zea to indoxacarb, methomyl, spinetoram, and spinosad in Puerto Rico, and may facilitate the detection of field-selected resistance for these two species and their potential hybrids in areas recently invaded by H. armigera. Full article

(This article belongs to the Special Issue Invasive Arthropod Pests)

13 pages, 1250 KiB

Open AccessArticle

Parasitism of Locally Recruited Egg Parasitoids of the Fall Armyworm in Africa

by Saidou A. Laminou, Malick Niango Ba, Laouali Karimoune, Ali Doumma and Rangaswamy Muniappan

Insects 2020, 11(7), 430; https://doi.org/10.3390/insects11070430 - 09 Jul 2020

Cited by 24 | Viewed by 5614

Abstract

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way [...] Read more.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way of combatting the pest and contributes to an integrated pest management approach. In Africa, several trichogrammatid parasitoids and Telenomus remus Nixon (Hymenoptera: Platygastridae) have been found parasitizing eggs of the FAW. In Niger, the egg parasitoids encountered include Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae) and Telenomus remus Nixon. Parasitism of the FAW eggs by the two egg parasitoids was assessed in the laboratory, followed by field testing on sentinel eggs. In the laboratory, T. remus parasitized on average 78% of FAW eggs, compared to 25% for Trichogrammatoidea sp. Telenomus remus was able to parasitize egg masses that were fully covered with scales, while Trichogrammatoidea sp. parasitized only uncovered egg masses. On-farm releases of T. remus in sorghum fields caused up to 64% of FAW egg parasitism. Parasitized eggs yielded viable progeny, which can contribute to FAW egg parasitism build-up during the cropping season. Our findings lay the groundwork for the use of T. remus in augmentative releases against FAW in Africa. Full article

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11 pages, 1659 KiB

Open AccessArticle

Delving into the Causes and Effects of Entomopathogenic Endophytic Metarhizium brunneum Foliar Application-Related Mortality in Spodoptera littoralis Larvae

by Inmaculada Garrido-Jurado, David Montes-Moreno, Pilar Sanz-Barrionuevo and Enrique Quesada-Moraga

Insects 2020, 11(7), 429; https://doi.org/10.3390/insects11070429 - 09 Jul 2020

Cited by 10 | Viewed by 2659

Abstract

The aim of the current study was to delve into the causes of mortality of Spodoptera littoralis larvae feeding on Metarhizium-colonized plants in the absence of fungal outgrowth on the cadavers as previous studies reported and to elucidate the possible indirect effects [...] Read more.

The aim of the current study was to delve into the causes of mortality of Spodoptera littoralis larvae feeding on Metarhizium-colonized plants in the absence of fungal outgrowth on the cadavers as previous studies reported and to elucidate the possible indirect effects of this fungus-colonized diet. The effect was evaluated in experiments conducted using leaf discs of colonized plants and in planta using fungus-colonized whole plants. The mortality rates of larvae fed on Metarhizium-colonized melon leaves were 45.0% and 87.5%, and the average survival times were 6.6 and 3.1 days in experiments performed with discs and in planta, respectively. Notably, these mortality levels were not associated with observed apoptosis mediated by caspases 1, 3-7 and 8; thus, further investigation into the possible immune system reaction of the insect after the ingestion of colonized plants is required. The leaf consumption of S. littoralis larvae fed on melon-colonized leaves was lower than that on control plants in the disc experiments but not in experiments conducted in planta. In this regard, in experiments performed in planta, plant damage increased larval mortality in both fungally challenged and control larvae. There was also a meaningful effect of exposure to Metarhizium-colonized melon leaf discs on S. littoralis fitness, with significant reductions in 39.0% and 22.0% in female fecundity and egg fertility, respectively, detected in females emerging from pupae developing from larvae surviving exposure to colonized plant discs; all larvae died in the in planta experiments. Hence, the present work presents new findings revealing the high potential of endophytic entomopathogenic fungi to improve the outcome of foliar applications against chewing insects in the short, mid- and long term, by the reduction of the reproductive potential of surviving adults and reveals new insights into the development of bioassays with whole plants for more detailed evaluation of the impact of these fungi as endophytes used for plant protection. Full article

(This article belongs to the Special Issue Control of Insect Pests using Entomopathogenic Fungi (EF) and Their Bioactive Compounds)

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13 pages, 789 KiB

Open AccessArticle

Cold Storage Effects on Fitness of the Whitefly Parasitoids Encarsia sophia and Eretmocerus hayati

by Dawit Kidane, Marco Ferrante, Xiao-Ming Man, Wan-Xue Liu, Fang-Hao Wan and Nian-Wan Yang

Insects 2020, 11(7), 428; https://doi.org/10.3390/insects11070428 - 09 Jul 2020

Cited by 3 | Viewed by 2584

Abstract

Successful biological control of the whitefly Bemisia tabaci involves the mass rearing of biocontrol agents in large numbers for field release. Cold storage of the biocontrol agents is often necessary to provide a sufficient number of biocontrol agents during an eventual pest outbreak. [...] Read more.

Successful biological control of the whitefly Bemisia tabaci involves the mass rearing of biocontrol agents in large numbers for field release. Cold storage of the biocontrol agents is often necessary to provide a sufficient number of biocontrol agents during an eventual pest outbreak. In this study, the fitness of two whitefly parasitoids Encarsia sophia Girault and Dodd (Hymenoptera: Aphelinidae) and Eretmocerus hayati Zolnerowich and Rose (Hymenoptera: Aphelinidae) was evaluated under fluctuating cold storage temperatures. The emergence rate of old pupae of either species was not affected when stored at 12, 10, 8 and 6 °C for 1 week. Cold storage had no effect on the longevity of the emerging adult En. sophia except young pupae stored at 4 °C, while Er. hayati was negatively affected after 2 weeks of storage time at all temperatures. Parasitism by adults emerging from older pupae stored at 12 °C for 1 week was equivalent to the control. Combined with the results for the emergence time, we suggest that the old pupal stage of En. sophia and Er. hayati could be stored at 12 and 10 °C, respectively (transferred every 22 h to 26 ± 1 °C for 2 h), for 1 week, with no or little adverse effect. Full article

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17 pages, 2922 KiB

Open AccessArticle

Dispersal of the Common Cutworm, Spodoptera litura, Monitored by Searchlight Trap and Relationship with Occurrence of Soybean Leaf Damage

by Akira Otuka, Masaya Matsumura and Makoto Tokuda

Insects 2020, 11(7), 427; https://doi.org/10.3390/insects11070427 - 09 Jul 2020

Cited by 8 | Viewed by 2614

Abstract

The common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a major pest of soybean. Pheromone traps are used to monitor male adults, but the catch peaks do not always predict leaf damage in soybean fields. Thus, there is no accurate means of forecasting [...] Read more.

The common cutworm, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) is a major pest of soybean. Pheromone traps are used to monitor male adults, but the catch peaks do not always predict leaf damage in soybean fields. Thus, there is no accurate means of forecasting soybean damage, and insecticide is applied on the basis of farmers’ observations of actual damage in fields. To understand the occurrence of soybean leaf damage, the dispersal of S. litura in a soybean field in southwestern Japan was preliminarily investigated using a searchlight trap in comparison to a pheromone trap at one location, from August to mid-October in 2016–2018. To determine the relationship between pest arrival and crop damage, trap catch numbers and the number of soybean leaves damaged by 1st-instar larvae were examined by separately comparing raw numbers and cumulative numbers. The raw catch numbers of the two trap types in August and September 2016 and 2018 preceded subsequent damage peaks by an average of 5.3 days. This temporal difference coincided with the estimated duration of the egg stage plus an assumed mating period. Furthermore, the cumulative catch numbers of the two traps in August and September were linearly associated with cumulative damaged leaves in the same period in each year and in the three-year period. The coefficient of determination (R²) of linear regression between the cumulative catch numbers of the searchlight trap and the cumulative damaged leaves for the three-year period was much higher than that between the cumulative catch of the pheromone trap and cumulative damage. This suggests that soybean leaf damage is closely linked to the number of S. litura arrivals at the survey site. Thus, the searchlight trap captured S. litura arrivals better than the pheromone trap. As the linear regression function of the cumulative catch of the searchlight trap for the three-year period was tentatively correlated with a prefectural economic injury level for soybean fields, it might be feasible to predict S. litura-induced soybean damage using searchlight traps. The cumulative female catch number of the searchlight trap was also linearly associated with damaged leaves, but the coefficient of determination was generally lower than that with the cumulative total catch. The female ratio of searchlight trap catches in September was <0.5 in contrast to S. litura migrating overseas (>0.5). The advantages and disadvantages of the two trapping methods, as well as necessary further studies are discussed. Our findings provide a foundation for S. litura monitoring with searchlight traps. Full article

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16 pages, 2488 KiB

Open AccessArticle

Foliage Intensity is an Important Cue of Habitat Location for Empoasca onukii

by Lei Bian, Xiao Ming Cai, Zong Xiu Luo, Zhao Qun Li and Zong Mao Chen

Insects 2020, 11(7), 426; https://doi.org/10.3390/insects11070426 - 09 Jul 2020

Cited by 10 | Viewed by 2638

Abstract

For many herbivorous insects, vision is more important than olfaction in the prealighting stage of host habitat location. Tea leafhoppers, Empoasca onukii (Hemiptera, Cicadellidae), are serious pests that preferentially inhabit the tender leaves of tea plants across China. Here, we investigated whether tea [...] Read more.

For many herbivorous insects, vision is more important than olfaction in the prealighting stage of host habitat location. Tea leafhoppers, Empoasca onukii (Hemiptera, Cicadellidae), are serious pests that preferentially inhabit the tender leaves of tea plants across China. Here, we investigated whether tea leafhoppers could distinguish foliage colors associated with different leaf ages and use this visual cue to guide suitable habitat location from short distances. Similar to honeybees, the adult E. onukii has an apposition type of compound eye, and each ommatidium has eight retinular cells, in which three spectral types of photoreceptors are distributed, with peak sensitivities at 356 nm (ultraviolet), 435 nm (blue), and 542 nm (green). Both changes in spectral intensity and hue of reflectance light of the host foliage were correlated with varying leaf age, and the intensity linearly decreased with increasing leaf age. Behavioral responses also showed that adult E. onukii could discriminate between the simulated colors of host foliage at different leaf ages without olfactory stimuli and selected the bright colors that strongly corresponded to those of tender leaves. The results suggest that, compared with the spectral composition (hue), the intensity of light reflectance from leaves at different ages is more important for adult leafhoppers when discriminating host foliage and could guide them to tender leaves at the top of tea shoots. Full article

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