Next Issue
Previous Issue

Table of Contents

Insects, Volume 9, Issue 2 (June 2018)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-37
Export citation of selected articles as:
Open AccessReview Transmission Success of Entomopathogenic Nematodes Used in Pest Control
Received: 24 May 2018 / Revised: 15 June 2018 / Accepted: 18 June 2018 / Published: 20 June 2018
PDF Full-text (2769 KB) | HTML Full-text | XML Full-text
Abstract
Entomopathogenic nematodes from the two genera Steinernema and Heterorhabditis are widely used as biological agents against various insect pests and represent a promising alternative to replace pesticides. Efficacy and biocontrol success can be enhanced through improved understanding of their biology and ecology. Many
[...] Read more.
Entomopathogenic nematodes from the two genera Steinernema and Heterorhabditis are widely used as biological agents against various insect pests and represent a promising alternative to replace pesticides. Efficacy and biocontrol success can be enhanced through improved understanding of their biology and ecology. Many endogenous and environmental factors influence the survival of nematodes following application, as well as their transmission success to the target species. The aim of this paper is to give an overview of the major topics currently considered to affect transmission success of these biological control agents, including interactions with insects, plants and other members of the soil biota including conspecifics. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Figure 1

Open AccessArticle Spatial Distribution of Bactrocera dorsalis and Thaumatotibia leucotreta in Smallholder Avocado Orchards along Altitudinal Gradient of Taita Hills and Mount Kilimanjaro
Received: 10 May 2018 / Revised: 8 June 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
PDF Full-text (804 KB) | HTML Full-text | XML Full-text
Abstract
Avocado (Persea americana) fruits are an important source of income and a nutritious food for small-scale growers and other stakeholders involved in farming along the Afrotropical highlands of Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. Avocado fruits are
[...] Read more.
Avocado (Persea americana) fruits are an important source of income and a nutritious food for small-scale growers and other stakeholders involved in farming along the Afrotropical highlands of Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. Avocado fruits are infested by several insect pests, namely the Asian invasive fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and the false codling moth, Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae). However, there is inadequate information on the distribution patterns of these pests in small-scale avocado cropping systems in the East African highlands. This study was initiated to generate a spatial distribution map of B. dorsalis and T. leucotreta in avocado orchards at Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. The two pests were monitored by using their respective parapheromone lures for two years between August 2012 and July 2014. Fruit damage was assessed by computing the proportion of infested fruits for B. dorsalis, whereas the damage score was used for T. leucotreta. Our results indicated that the mean number of B. dorsalis per trap per day differed significantly across elevation, being highest in lowland zone for both Taita Hills (15.90) and Mount Kilimanjaro (24.45). Similarly, the percentage infestation of ground collected fruits by B. dorsalis varied with altitude, being lowest at highlands above 1500 m.a.s.l. (0.66% and 0.83% for Taita Hills and Mount Kilimanjaro, respectively). Conversely, the mean number of T. leucotreta did not vary with altitude in either study area. However, the damage score for T. leucotreta infestation was significantly lower in the highlands of both transects (7.0% and11.1% for Taita Hills and Mount Kilimanjaro, respectively). These findings describe spatial trends that are important in formulating strategies aimed at suppressing the populations of B. dorsalis and T. leucotreta in East African avocado cropping systems. Full article
Figures

Figure 1

Open AccessArticle Susceptibility of Duponchelia fovealis Zeller (Lepidoptera: Crambidae) to Soil-Borne Entomopathogenic Fungi
Received: 1 May 2018 / Revised: 8 June 2018 / Accepted: 11 June 2018 / Published: 19 June 2018
PDF Full-text (821 KB) | HTML Full-text | XML Full-text
Abstract
Duponchelia fovealis (Lepidoptera: Crambidae) is an invasive species that has had a large impact on strawberry crops in Brazil. Pesticides have had limited effectiveness and the use of biological control agents to improve its management is the most appropriate approach. The aim of
[...] Read more.
Duponchelia fovealis (Lepidoptera: Crambidae) is an invasive species that has had a large impact on strawberry crops in Brazil. Pesticides have had limited effectiveness and the use of biological control agents to improve its management is the most appropriate approach. The aim of this study was to evaluate the pathogenicity and virulence of entomopathogenic fungi—isolated from soil—against Duponchelia fovealis larvae under laboratory and greenhouse conditions. Pathogenicity screenings were performed for twenty isolates from Beauveria bassiana, Beauveria caledonica, Isaria javanica, Metarhizium anisopliae, and Lecanicillium sp. against third instar larvae of D. fovealis at the concentration of 109 conidia·mL−1. Lethal concentration (LC50) and lethal time (LT50) were determined for the most pathogenic isolates and for one commercial mycoinsecticide. Mortality rates varied from 10 to 89%. The isolates B. bassiana Bea1, Bea110, Bea111 and I. javanica Isa340 were the most pathogenic. The most virulent isolates were B. bassiana Bea111 and I. javanica Isa340 with LC50 values of 2.33 × 106 and 9.69 × 105 conidia·mL−1, respectively. Under greenhouse conditions, the efficacy of LC50 of the isolates I. javanica Isa340 and B. bassiana Bea111 were 45% and 52%, respectively. Our results indicate that these isolates are strong candidates for application in the control of D. fovealis. This study is the first evaluation of soil-borne entomopathogenic fungi against D. fovealis. Full article
Figures

Graphical abstract

Open AccessArticle Prediction of Sporulation and Germination by the Spider Mite Pathogenic Fungus Neozygites floridana (Neozygitomycetes: Neozygitales: Neozygitaceae) Based on Temperature, Humidity and Time
Insects 2018, 9(2), 69; https://doi.org/10.3390/insects9020069 (registering DOI)
Received: 11 May 2018 / Revised: 7 June 2018 / Accepted: 14 June 2018 / Published: 19 June 2018
PDF Full-text (2228 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Neozygites floridana is a pathogenic fungus and natural enemy of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), which is an important polyphagous plant pest. The aim of this study was to reveal and predict what combination of temperature, relative humidity (RH), and
[...] Read more.
Neozygites floridana is a pathogenic fungus and natural enemy of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), which is an important polyphagous plant pest. The aim of this study was to reveal and predict what combination of temperature, relative humidity (RH), and time that enables and promotes primary conidia production and capilliconidia formation in N. floridana (Brazilian isolate ESALQ 1420), in both a detached leaf assay mimicking climatic conditions in the leaf boundary layer and in a semi-field experiment. In the detached leaf assay, a significant number of conidia were produced at 90% RH but the highest total number of primary conidia and proportion of capilliconidia was found at 95 and 100% RH at 25 °C. Positive temperature and RH effects were observed and conidia production was highest in the 8 to 12 h interval. The semi-field experiment showed that for a >90% probability of N. floridana sporulation, a minimum of 6 h with RH >90% and 10 h with temperatures >21 °C, or 6 h with temperatures >21 °C and 15 h with RH >90% was needed. Our study identified suitable conditions for primary- and capilliconidia production in this Brazilian N. floridana isolate. This information provides an important base for building models of a Decision Support System (DSS) where this natural enemy may be used as a tool in Integrated Pest Management (IPM) and a base for developing in vivo production systems of N. floridana. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Figure 1

Open AccessFeature PaperReview Secretion Systems and Secreted Proteins in Gram-Negative Entomopathogenic Bacteria: Their Roles in Insect Virulence and Beyond
Received: 13 May 2018 / Revised: 11 June 2018 / Accepted: 13 June 2018 / Published: 19 June 2018
PDF Full-text (232 KB) | HTML Full-text | XML Full-text
Abstract
Many Gram-negative bacteria have evolved insect pathogenic lifestyles. In all cases, the ability to cause disease in insects involves specific bacterial proteins exported either to the surface, the extracellular environment, or the cytoplasm of the host cell. They also have several distinct mechanisms
[...] Read more.
Many Gram-negative bacteria have evolved insect pathogenic lifestyles. In all cases, the ability to cause disease in insects involves specific bacterial proteins exported either to the surface, the extracellular environment, or the cytoplasm of the host cell. They also have several distinct mechanisms for secreting such proteins. In this review, we summarize the major protein secretion systems and discuss examples of secreted proteins that contribute to the virulence of a variety of Gram-negative entomopathogenic bacteria, including Photorhabdus, Xenorhabdus, Serratia, Yersinia, and Pseudomonas species. We also briefly summarize two classes of exported protein complexes, the PVC-like elements, and the Tc toxin complexes that were first described in entomopathogenic bacteria. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Open AccessArticle Influence of Elytral Color Pattern, Size, and Sex of Harmonia axyridis (Coleoptera, Coccinellidae) on Parasite Prevalence and Intensity of Hesperomyces virescens (Ascomycota, Laboulbeniales)
Received: 20 May 2018 / Revised: 12 June 2018 / Accepted: 12 June 2018 / Published: 15 June 2018
PDF Full-text (688 KB) | HTML Full-text | XML Full-text
Abstract
Harmonia axyridis is an invasive ladybird (Coleoptera, Coccinellidae) with the potential to outcompete native ladybird species in its invasive distribution area. It was introduced as a biological control agent in many countries but has also spread unintentionally in many others. Hesperomyces virescens (Ascomycota,
[...] Read more.
Harmonia axyridis is an invasive ladybird (Coleoptera, Coccinellidae) with the potential to outcompete native ladybird species in its invasive distribution area. It was introduced as a biological control agent in many countries but has also spread unintentionally in many others. Hesperomyces virescens (Ascomycota, Laboulbeniales) is a minute (200–400 µm in size) biotrophic fungus that infects over 30 species of ladybirds. The aim of this study was to evaluate whether the elytral color pattern, size, and sex of Ha. axyridis affect infection by H. virescens. Coloration in Ha. axyridis has been linked to the presence of an antimicrobial alkaloid (harmonine). In fall 2016, we collected 763 Ha. axyridis individuals in Cambridge, Massaschusetts, of which 119 (16%) bore H. virescens fruiting bodies. We analyzed 160 individuals (80 infected, 80 uninfected) concerning the intensity of infection by H. virescens. Elytral sizes and coloration patterns were quantified using digital photography and analytical methods. Smaller ladybirds had a higher prevalence and higher intensity of parasitism. Additionally, male ladybirds bore more thalli compared to female ladybirds. Elytral color patterns had an effect on neither prevalence nor intensity of infection by Laboulbeniales in our dataset, although we found a slight trend to higher intensity of parasitism in more melanic males. This suggests that the development of Laboulbeniales might be affected by certain insect alkaloids. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Figure 1

Open AccessArticle Research on Vegetable Pest Warning System Based on Multidimensional Big Data
Received: 20 April 2018 / Revised: 10 June 2018 / Accepted: 11 June 2018 / Published: 13 June 2018
PDF Full-text (2504 KB) | HTML Full-text | XML Full-text
Abstract
Pest early warning technology is part of the prerequisite for the timely and effective control of pest outbreaks. Traditional pest warning system with artificial mathematical statistics, radar, and remote sensing has some deficiency in many aspects, such as higher cost, weakness of accuracy,
[...] Read more.
Pest early warning technology is part of the prerequisite for the timely and effective control of pest outbreaks. Traditional pest warning system with artificial mathematical statistics, radar, and remote sensing has some deficiency in many aspects, such as higher cost, weakness of accuracy, low efficiency, and so on. In this study, Pest image data was collected and information about four major vegetable pests (Bemisia tabaci (Gennadius), Phyllotreta striolata (Fabricius), Plutella xylostella (Linnaeus), and Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae)) in southern China was extracted. A multi-sensor network system was constructed to collect small-scale environmental data on vegetable production sites. The key factors affecting the distribution of pests were discovered by multi-dimensional information, such as soil, environment, eco-climate, and meteorology of vegetable fields, and finally, the vegetable pest warning system that is based on multidimensional big data (VPWS-MBD) was implemented. Pest and environmental data from Guangzhou Dongsheng Bio-Park were collected from June 2017 to February 2018. The number of pests is classified as level I (0–56), level II (57–131), level III (132–299), and level IV (above 300) by K-Means algorithm. The Pearson correlation coefficient and the grey relational analysis algorithm were used to calculate the five key influence factors of rainfall, soil temperature, air temperature, leaf surface humidity, and soil moisture. Finally, Back Propagation (BP) Neural Network was used for classification prediction. The result shows: I-level warning accuracy was 96.14%, recall rate was 97.56%; II-level pest warning accuracy was 95.34%, the recall rate was 96.45%; III-level pest warning accuracy of 100%, the recall rate was 96.28%; IV-level pest warning accuracy of 100%, recall rate was 100%. It proves that the early warning system can effectively predict vegetable pests and achieve the early warning of vegetable pest’s requirements, with high availability. Full article
(This article belongs to the Special Issue Insect Monitoring and Trapping in Agricultural Systems)
Figures

Figure 1

Open AccessFeature PaperArticle Honey Bee Survival and Pathogen Prevalence: From the Perspective of Landscape and Exposure to Pesticides
Received: 23 March 2018 / Revised: 1 June 2018 / Accepted: 11 June 2018 / Published: 13 June 2018
PDF Full-text (1867 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In order to study the in situ effects of the agricultural landscape and exposure to pesticides on honey bee health, sixteen honey bee colonies were placed in four different agricultural landscapes. Those landscapes were three agricultural areas with varying levels of agricultural intensity
[...] Read more.
In order to study the in situ effects of the agricultural landscape and exposure to pesticides on honey bee health, sixteen honey bee colonies were placed in four different agricultural landscapes. Those landscapes were three agricultural areas with varying levels of agricultural intensity (AG areas) and one non-agricultural area (NAG area). Colonies were monitored for different pathogen prevalence and pesticide residues over a period of one year. RT-qPCR was used to study the prevalence of seven different honey bee viruses as well as Nosema sp. in colonies located in different agricultural systems with various intensities of soybean, corn, sorghum, and cotton production. Populations of the parasitic mite Varroa destructor were also extensively monitored. Comprehensive MS-LC pesticide residue analyses were performed on samples of wax, honey, foragers, winter bees, dead bees, and crop flowers for each apiary and location. A significantly higher level of varroa loads were recorded in colonies of the AG areas, but this at least partly correlated with increased colony size and did not necessarily result from exposure to pesticides. Infections of two viruses (deformed wing virus genotype a (DWVa) and acute bee paralysis virus (ABPV)) and Nosema sp. varied among the four studied locations. The urban location significantly elevated colony pathogen loads, while AG locations significantly benefited and increased the colony weight gain. Cotton and sorghum flowers contained high concentrations of insecticide including neonicotinoids, while soybean and corn had less pesticide residues. Several events of pesticide toxicity were recorded in the AG areas, and high concentrations of neonicotinoid insecticides were detected in dead bees. Full article
(This article belongs to the Special Issue Stressors on Bee Health)
Figures

Graphical abstract

Open AccessArticle Within-Host Competition between Two Entomopathogenic Fungi and a Granulovirus in Diatraea saccharalis (Lepidoptera: Crambidae)
Received: 2 May 2018 / Revised: 30 May 2018 / Accepted: 1 June 2018 / Published: 13 June 2018
PDF Full-text (483 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We provide insights into how the interactions of two entomopathogenic fungi and a virus play a role in virulence, disease development, and pathogen reproduction for an economically important insect crop pest, the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). In our model system,
[...] Read more.
We provide insights into how the interactions of two entomopathogenic fungi and a virus play a role in virulence, disease development, and pathogen reproduction for an economically important insect crop pest, the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). In our model system, we highlight the antagonistic effects of the co-inoculation of Beauveria bassiana and granulovirus (DisaGV) on virulence, compared to their single counterparts. By contrast, combinations of Metarhizium anisopliae and B. bassiana, or M. anisopliae and DisaGV, have resulted in additive effects against the insect. Intriguingly, most cadavers that were derived from dual or triple infections, produced signs/symptoms of only one species after the death of the infected host. In the combination of fungi and DisaGV, there was a trend where a higher proportion of viral infection bearing conspicuous symptoms occurred, except when the larvae were inoculated with M. anisopliae and DisaGV at the two highest inoculum rates. Co-infections with B. bassiana and M. anisopliae did not affect pathogen reproduction, since the sporulation from co-inoculated larvae did not differ from their single counterparts. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Graphical abstract

Open AccessArticle Resistance to Permethrin, β-cyfluthrin, and Diazinon in Florida Horn Fly Populations
Received: 10 April 2018 / Revised: 25 May 2018 / Accepted: 7 June 2018 / Published: 12 June 2018
PDF Full-text (701 KB) | HTML Full-text | XML Full-text
Abstract
Horn flies, Haematobia irritans, a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population,
[...] Read more.
Horn flies, Haematobia irritans, a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population, with the greatest resistance exhibited by a 66-fold resistance ratio (RR) to permethrin and >14-fold RR to diazinon. Mechanisms of resistance were determined using molecular techniques and enzymatic assays. The knockdown resistance (kdr) genotype (L150F) associated with pyrethroid resistance, and a G262A mutation in acetylcholinesterase, previously associated with organophosphate resistance, were found in all field populations evaluated. Insensitivity of diazoxon at the acetylcholinesterase (AChE) target site was significantly different in horn flies from one of the field sites. For metabolic detoxifying enzymes, cytochrome P450 nor general esterases showed a significant difference between field strains and a laboratory susceptible strain. Pyrethroid resistance was likely due to the presence of the L150F mutation in the population. In vitro studies targeting the AChE enzyme did not support the notion that the G262A mutation was the sole cause of resistance to organophosphates, and, therefore, the exact resistance mechanism to diazinon was not able to be confirmed. Full article
Figures

Figure 1

Open AccessArticle Expression of Resistance in Amaranthus spp. (Caryophyllales: Amaranthaceae): Effects of Selected Accessions on the Behaviour and Biology of the Amaranth Leaf-Webber, Spoladea recurvalis (Lepidoptera: Crambidae)
Received: 16 April 2018 / Revised: 4 June 2018 / Accepted: 6 June 2018 / Published: 8 June 2018
PDF Full-text (1270 KB) | HTML Full-text | XML Full-text
Abstract
Spoladea recurvalis F. is a major pest moth of amaranth (Amaranthus spp.) flowers worldwide, with a potential of causing complete foliage loss under severe outbreaks. Chemical insecticides are uneconomical for resource-poor farmers and pose health and environmental risks. Host plant resistance (HPR)
[...] Read more.
Spoladea recurvalis F. is a major pest moth of amaranth (Amaranthus spp.) flowers worldwide, with a potential of causing complete foliage loss under severe outbreaks. Chemical insecticides are uneconomical for resource-poor farmers and pose health and environmental risks. Host plant resistance (HPR) to insects is an effective, economical and environmentally friendly alternative that is poorly understood and largely unexploited among traditional leafy vegetables. A total of 35 amaranth accessions were evaluated for the expression of their antixenotic and antibiotic traits against S. recurvalis, focusing on their effects on the biology of the pest in comparison with a susceptible accession. The accession VI036227 was found to be highly resistant against the pest, exhibiting exemplary antibiosis by causing 100% larval mortality within the first 36 h, despite not being deterrent for oviposition. The accessions VI048076, VI056563 and VI047555-B demonstrated moderate resistance against the pest for specific parameters including low oviposition, moderate early stage larval mortality and reduced adult longevity. Total mortality and weight gain in these three accessions were, however, not significantly different from the susceptible control. Higher numbers of eggs were laid in no-choice compared to choice situations. The implications of these findings in the management of S. recurvalis on amaranths are discussed. Full article
Figures

Figure 1

Open AccessArticle Frequent Insect Visitors Are Not Always Pollen Carriers in Hybrid Carrot Pollination
Received: 11 April 2018 / Revised: 22 May 2018 / Accepted: 1 June 2018 / Published: 7 June 2018
PDF Full-text (1381 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Insect crop visitations do not necessarily translate to carriage or transfer of pollen. To evaluate the potential of the various insects visiting hybrid carrot flowers to facilitate pollen transfer, this study examines insect visitation rates to hybrid carrot seed crops in relation to
[...] Read more.
Insect crop visitations do not necessarily translate to carriage or transfer of pollen. To evaluate the potential of the various insects visiting hybrid carrot flowers to facilitate pollen transfer, this study examines insect visitation rates to hybrid carrot seed crops in relation to weather, time of day and season, pollen carrying capacity, inter-row movement, and visitation frequency to male-fertile and male-sterile umbels. The highest pollen loads were carried by nectar scarabs, honey bees, and the hover fly Eristalis tenax (Linnaeus). Honey bees and muscoid flies were observed to forage mostly within the male fertile carrot row while nectar scarabs and E. tenax foraged across rows, carrying equal pollen loads regardless of their distance from the pollen source. All observed insect taxa were more frequently seen visiting male-fertile than male-sterile umbels. In contrast to other visiting insects, honey bees were abundant and frequent visitors and were observed carrying high pollen loads. Consequently, we suggest both optimizing honey bee management and improving the attraction of carrot lines to honey bees to improve pollination rates for hybrid carrot seed crops. Full article
Figures

Figure 1

Open AccessArticle Effect of the Topical Repellent para-Menthane-3,8-diol on Blood Feeding Behavior and Fecundity of the Dengue Virus Vector Aedes aegypti
Received: 13 April 2018 / Revised: 23 May 2018 / Accepted: 25 May 2018 / Published: 4 June 2018
PDF Full-text (1923 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dengue fever is an acute disease caused by the dengue virus and transmitted primarily by the mosquito Aedes aegypti. The current strategy for dengue prevention is vector control including the use of topical repellents to reduce mosquito biting. Although N,N
[...] Read more.
Dengue fever is an acute disease caused by the dengue virus and transmitted primarily by the mosquito Aedes aegypti. The current strategy for dengue prevention is vector control including the use of topical repellents to reduce mosquito biting. Although N,N-diethyl-m-methylbenzamide (DEET) is the most common active ingredient in topical repellent products, para-menthane-3,8-diol (PMD) is also used commercially. Studies have indicated PMD reduced biting by 90–95% for up to 6–8 h, similar to the efficacy of DEET, depending on the testing environment. The purpose of this study was to evaluate the behavioral effects of PMD on Ae. aegypti blood feeding and fecundity to explore the potential impact of PMD on downstream mosquito life-history traits. Two experiments were performed. In both experiments, cohorts of female Ae. aegypti (Belize strain) were exposed to 20% PMD or ethanol for 10 min in a closed system and introduced to an artificial membrane feeding system. Following a 30min feed time, mosquitoes of Experiment 1 were killed and weighed as a proxy measure of blood meal, whereas mosquitoes of Experiment 2 were monitored for oviposition, a measure of fecundity. Results showed a statistically significant reduction (p < 0.001) in the percentage of Ae. aegypti that blood-fed when exposed to PMD (38%) compared to those non-exposed (49%). No significant difference in fecundity between test populations was indicated. These findings suggest that exposure of Ae. aegypti to 20% PMD may influence the probability of subsequent blood feeding but of those mosquitoes that do blood feed, egg-lay density is not affected. Further studies are warranted to investigate the full range of effects of PMD exposure on other Ae. aegypti life-history traits such as mating, to continue characterizing the potential effects of PMD to impact overall vector population dynamics. Full article
(This article belongs to the Special Issue Integrated Pest Management)
Figures

Figure 1

Open AccessArticle Host-Specific Activation of Entomopathogenic Nematode Infective Juveniles
Received: 1 May 2018 / Revised: 28 May 2018 / Accepted: 1 June 2018 / Published: 2 June 2018
PDF Full-text (1314 KB) | HTML Full-text | XML Full-text
Abstract
Entomopathogenic nematodes (EPNs) are potent insect parasites and have been used for pest control in agriculture. Despite the complexity of the EPN infection process, hosts are typically killed within 5 days of initial infection. When free-living infective juveniles (IJs) infect a host, they
[...] Read more.
Entomopathogenic nematodes (EPNs) are potent insect parasites and have been used for pest control in agriculture. Despite the complexity of the EPN infection process, hosts are typically killed within 5 days of initial infection. When free-living infective juveniles (IJs) infect a host, they release their bacterial symbiont, secrete toxic products, and undergo notable morphological changes. Collectively, this process is referred to as “activation” and represents the point in a nematode’s life cycle when it becomes actively parasitic. The effect of different host tissues and IJ age on activation, and how activation itself is related to virulence, are not well understood. Here, we employed a recently developed bioassay, which quantifies IJ activation, as a tool to address these matters. Appreciating that activation is a key part of the EPN infection process, we hypothesized that activation would positively correlate to virulence. Using the EPNs Steinernema carpocapsae and S. feltiae we found that EPN activation is host-specific and influenced by infective juvenile age. Additionally, our data suggest that activation has a context-dependent influence on virulence and could be predictive of virulence in some cases such as when IJ activation is especially low. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Figure 1

Open AccessFeature PaperCommunication Camponotus floridanus Ants Incur a Trade-Off between Phenotypic Development and Pathogen Susceptibility from Their Mutualistic Endosymbiont Blochmannia
Received: 30 April 2018 / Revised: 23 May 2018 / Accepted: 30 May 2018 / Published: 1 June 2018
PDF Full-text (1050 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Various insects engage in microbial mutualisms in which the reciprocal benefits exceed the costs. Ants of the genus Camponotus benefit from nutrient supplementation by their mutualistic endosymbiotic bacteria, Blochmannia, but suffer a cost in tolerating and regulating the symbiont. This cost suggests
[...] Read more.
Various insects engage in microbial mutualisms in which the reciprocal benefits exceed the costs. Ants of the genus Camponotus benefit from nutrient supplementation by their mutualistic endosymbiotic bacteria, Blochmannia, but suffer a cost in tolerating and regulating the symbiont. This cost suggests that the ants face secondary consequences such as susceptibility to pathogenic infection and transmission. In order to elucidate the symbiont’s effects on development and disease defence, Blochmannia floridanus was reduced in colonies of Camponotus floridanus using antibiotics. Colonies with reduced symbiont levels exhibited workers of smaller body size, smaller colony size, and a lower major-to-minor worker caste ratio, indicating the symbiont’s crucial role in development. Moreover, these ants had decreased cuticular melanisation, yet higher resistance to the entomopathogen Metarhizium brunneum, suggesting that the symbiont reduces the ants’ ability to fight infection, despite the availability of melanin to aid in mounting an immune response. While the benefits of improved growth and development likely drive the mutualism, the symbiont imposes a critical trade-off. The ants’ increased susceptibility to infection exacerbates the danger of pathogen transmission, a significant risk given ants’ social lifestyle. Thus, the results warrant research into potential adaptations of the ants and pathogens that remedy and exploit the described disease vulnerability. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Figures

Graphical abstract

Back to Top