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Insects, Volume 10, Issue 7 (July 2019)

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Cover Story (view full-size image) Ticks are vectors of many pathogens that infect humans and animals worldwide. Because of global [...] Read more.
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Open AccessArticle
Diversity of Ants and Termites of the Botanical Garden of the University of Lomé, Togo
Insects 2019, 10(7), 218; https://doi.org/10.3390/insects10070218
Received: 6 June 2019 / Revised: 18 July 2019 / Accepted: 22 July 2019 / Published: 23 July 2019
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Abstract
Ants and termites are used as bioindicators in many ecosystems. Little knowledge is available about them in Togo, especially ants. This study aimed to find out how ants and termites could be used to assess the restoration of former agricultural land. These insect [...] Read more.
Ants and termites are used as bioindicators in many ecosystems. Little knowledge is available about them in Togo, especially ants. This study aimed to find out how ants and termites could be used to assess the restoration of former agricultural land. These insect groups were sampled within six transects of 50 × 2 m2 (using pitfall traps, monoliths, baits for ants and hand sampling for termites) in two consecutive habitats: open area (grassland) and covered area (an artificial forest). Seventeen termite species and 43 ant species were collected. Seven ant species were specific to the covered area against four for the open area, while four unshared species of termite were found in the open area against three in the covered area. The presence of unshared species was linked to vegetation, as Trinervitermes (Holmgren, 1912), a grass feeding termite, was solely found in open area. Also, for some ant species like Cataulacus traegaordhi (Santschi, 1914), Crematogaster (Lund, 1831) species, Oecophylla longinoda (Latreille, 1802) and Tetraponera mocquerysi (Brown, 1960), all arboreal species, vegetation was a determining factor for their presence. The occurrence of these species together with Basidentitermes mactus (Sjöstedt, 1911), Strumigenys bernardi (Brown, 1960) and S. sistrura (Bolton, 1983), suggest a more advanced level of restoration of the covered area. Full article
(This article belongs to the Special Issue Ecology of Termites)
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Open AccessArticle
Cuticular Hydrocarbon Recognition in the Mating Behavior of Two Pissodes Species
Insects 2019, 10(7), 217; https://doi.org/10.3390/insects10070217
Received: 25 June 2019 / Revised: 16 July 2019 / Accepted: 19 July 2019 / Published: 23 July 2019
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Abstract
Two sibling weevil species, Pissodes strobi Peck and P. nemorensis Germar (Coleoptera: Curculionidae), can form reduced-fitness hybrids in the laboratory, but neither their premating isolation mechanisms nor mating behaviors are well-understood. Cuticular hydrocarbons (CHCs) have been reported as crucial chemical cues in mating [...] Read more.
Two sibling weevil species, Pissodes strobi Peck and P. nemorensis Germar (Coleoptera: Curculionidae), can form reduced-fitness hybrids in the laboratory, but neither their premating isolation mechanisms nor mating behaviors are well-understood. Cuticular hydrocarbons (CHCs) have been reported as crucial chemical cues in mating recognition in many insects, including weevils, and, thus, may also mediate the mating behavior of P. strobi and P. nemorensis. We conducted a series of behavioral observations, bioassays, and chemical analyses to investigate the role of CHCs in their mating behavior. Copulation behavior of both species followed similar steps: approaching, mounting, tapping, aedeagus extrusion, and copulation. In P. strobi, hexane extraction significantly reduced the number of successful male copulations compared with freeze-killed females. Conversely, significantly fewer P. nemorensis males copulated with dead females compared with live females. No significant differences were detected among hexane-extracted, freeze-killed or recoated female carcasses to P. nemorensis. These findings suggested that female cuticular extracts contain important cues in mate recognition in P. strobi but not in P. nemorensis. We identified 21 CHCs from both species with variation in abundances between sexes and seasons. Discriminant analysis revealed incomplete overlap of CHC compositions in females of the two species in summer, when hybridization potentially occurs. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Open AccessArticle
Pollen Release Dynamics and Daily Patterns of Pollen-Collecting Activity of Honeybee Apis mellifera and Bumblebee Bombus lantschouensis in Solar Greenhouse
Insects 2019, 10(7), 216; https://doi.org/10.3390/insects10070216
Received: 19 June 2019 / Revised: 13 July 2019 / Accepted: 17 July 2019 / Published: 22 July 2019
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Abstract
Pollen is important not only for pollination and fertilization of plants, but also for colony development of bee pollinators. Anther dehiscence determines the available pollen that can be collected by foragers. In China, honeybees and bumblebees are widely used as pollinators in solar [...] Read more.
Pollen is important not only for pollination and fertilization of plants, but also for colony development of bee pollinators. Anther dehiscence determines the available pollen that can be collected by foragers. In China, honeybees and bumblebees are widely used as pollinators in solar greenhouse agriculture. To better understand the effect of solar greenhouse microclimates on pollen release and pollen-foraging behaviour, we observed the anther dehiscence dynamics and daily pollen-collecting activity of Apis mellifera and Bombus lantschouensis during peach anthesis in a solar greenhouse in Beijing. Microclimate factors had a significant effect on anther dehiscence and bee foraging behaviour. The proportion of dehisced anthers increased with increasing temperature and decreasing relative humidity and peaked from 11:00 h to 14:00 h, coinciding with the peak pollen-collecting activity of bees. On sunny days, most pollen grains were collected by the two pollinators within two hours after anther dehiscence, at which time the viability of pollen had not yet significantly decreased. Our study helps us to better understand the relationship between food resources and pollinator foraging behaviour and to make better use of bees for pollination in Chinese solar greenhouses. Full article
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Open AccessReview
Local and Landscape Effects to Biological Controls in Urban Agriculture—A Review
Insects 2019, 10(7), 215; https://doi.org/10.3390/insects10070215
Received: 6 June 2019 / Revised: 15 July 2019 / Accepted: 16 July 2019 / Published: 22 July 2019
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Abstract
Urban agriculture is widely practiced throughout the world. Urban agriculture practitioners have diverse motivations and circumstances, but one problem is ubiquitous across all regions: insect pests. Many urban farmers and gardeners either choose to, or are required to forego, the use of chemical [...] Read more.
Urban agriculture is widely practiced throughout the world. Urban agriculture practitioners have diverse motivations and circumstances, but one problem is ubiquitous across all regions: insect pests. Many urban farmers and gardeners either choose to, or are required to forego, the use of chemical controls for pest outbreaks because of costs, overspray in populated areas, public health, and environmental concerns. An alternative form of pest control is conservation biological control (CBC)—a form of ecological pest management—that can reduce the severity of pest outbreaks and crop damage. Urban farmers relying on CBC often assume that diversification practices similar to those used in rural farms may reduce insect pest populations and increase populations of beneficial insects, yet these management practices may be inappropriate for applications in fragmented urban environments. In this review, we assess urban CBC research and provide a synthesis for urban agriculture practitioners. Our findings indicate that local and landscape factors differentially affect insect pests and beneficial arthropods across the reviewed studies, and we identify several on-farm practices that can be implemented to increase biological control in urban agriculture. Full article
(This article belongs to the Special Issue Urban Small Farms and Gardens Pest Management)
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Open AccessArticle
Impact of Exclusion Netting Row Covers on ‘Honeycrisp’ Apple Trees Grown under Northeastern North American Conditions: Effects on Photosynthesis and Fruit Quality
Insects 2019, 10(7), 214; https://doi.org/10.3390/insects10070214
Received: 13 June 2019 / Revised: 11 July 2019 / Accepted: 16 July 2019 / Published: 19 July 2019
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Abstract
Exclusion nets have been used successfully to protect fruit from insect pests of apples under various conditions, but the effect of each particular netting system on the plant itself has rarely been investigated. In this study, a complete exclusion system—in which the soil [...] Read more.
Exclusion nets have been used successfully to protect fruit from insect pests of apples under various conditions, but the effect of each particular netting system on the plant itself has rarely been investigated. In this study, a complete exclusion system—in which the soil is also excluded—was used to grow ‘Honeycrisp’ apples for six years in southern Quebec, Canada. Abiotic conditions, as well as plant photosynthesis and fruit quality characteristics (colour, firmness, size, sugar content, number of seeds, ripeness and skin integrity) and yield were estimated yearly and compared in netted (either with or without a rainproof top) and unnetted row units. Although annual variations were high and results showed little or no difference between netted and unnetted rows for all measured variables, with the following exceptions; colour (increased red surface on fruits from unnetted rows some years), size (fruits from unnetted rows were smaller) and maturity (fruits from unnetted rows matured slightly faster). Fruits produced under nets had fewer microcracks at the surface than fruits produced without nets. Reduced cracking possibly helped decrease sooty blotch and flyspeck incidence and severity. Impacts for pest control and prospects for pesticide-free production are discussed. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
Three Release Rates of Dicyphus hesperus (Hemiptera: Miridae) for Management of Bemisia tabaci (Hemiptera: Aleyrodidae) on Greenhouse Tomato
Insects 2019, 10(7), 213; https://doi.org/10.3390/insects10070213
Received: 11 June 2019 / Revised: 12 July 2019 / Accepted: 16 July 2019 / Published: 19 July 2019
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Abstract
The sweetpotato whitefly, Bemisia tabaci, is a pest of greenhouse-grown tomato. Restrictions on insecticides in enclosed structures and the presence of commercial pollinators limit the options for the chemical control of whiteflies in greenhouses, increasing the importance of biological controls. Dicyphus hesperus [...] Read more.
The sweetpotato whitefly, Bemisia tabaci, is a pest of greenhouse-grown tomato. Restrictions on insecticides in enclosed structures and the presence of commercial pollinators limit the options for the chemical control of whiteflies in greenhouses, increasing the importance of biological controls. Dicyphus hesperus is a zoophytophagous mirid predator native to North America. Three release rates of D. hesperus were evaluated on greenhouse tomato for control of the sweetpotato whitefly. The release rates were one, two or three adult D. hesperus per tomato plant each week for three weeks in cages containing four tomato plants and one mullein banker plant. There were fewer whitefly eggs in cages receiving predators than untreated cages one week after the third release, and fewer whitefly nymphs in cages receiving predators two weeks after the third release. There were no statistical differences in whitefly eggs or nymphs among predator release treatments. The highest release rate resulted in a 60% reduction in whitefly nymphs. Forty-two days after the first predator releases, there were no differences among release treatments in the number of D. hesperus. Our results indicate that D. hesperus can contribute management of B. tabaci on greenhouse tomato, but that it may be insufficient as a sole strategy. Full article
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Open AccessOpinion
The Probing Behavior Component of Disease Transmission in Insect-Transmitted Bacterial Plant Pathogens
Insects 2019, 10(7), 212; https://doi.org/10.3390/insects10070212
Received: 22 May 2019 / Revised: 8 July 2019 / Accepted: 15 July 2019 / Published: 19 July 2019
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Abstract
Insects can be effective vectors of plant diseases and this may result in billions of dollars in lost agricultural productivity. New, emerging or introduced diseases will continue to cause extensive damage in afflicted areas. Understanding how the vector acquires the pathogen and inoculates [...] Read more.
Insects can be effective vectors of plant diseases and this may result in billions of dollars in lost agricultural productivity. New, emerging or introduced diseases will continue to cause extensive damage in afflicted areas. Understanding how the vector acquires the pathogen and inoculates new hosts is critical in developing effective management strategies. Management may be an insecticide applied to kill the vector or a host plant resistance mechanism to make the host plant less suitable for the vector. In either case, the tactic must act before the insect performs the key behavior(s) resulting in either acquisition or transmission. This requires knowledge of the timing of behaviors the insect uses to probe the plant and commence ingestion. These behaviors are visualized using electropenetrography (EPG), wherein the plant and insect become part of an electrical circuit. With the tools to define specific steps in the probing process, we can understand the timing of acquisition and inoculation. With that understanding comes the potential for more relevant testing of management strategies, through insecticides or host plant resistance. The primary example will be Candidatus Liberibacter asiaticus transmitted by Diaphorina citri Kuwayama in the citrus agroecosystem, with additional examples used as appropriate. Full article
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Open AccessArticle
Diachasmimorpha longicaudata Parasitism Response to Medfly Host Fruit and Fruit Infestation Age
Insects 2019, 10(7), 211; https://doi.org/10.3390/insects10070211
Received: 30 May 2019 / Revised: 15 July 2019 / Accepted: 15 July 2019 / Published: 18 July 2019
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Abstract
The parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) is increasingly being used in integrated pest management (IPM) programs as a biological control agent in order to suppress tephritid fruit flies of economic importance. Innate and acquired behavioral responses—such as pest host fruit preference—of parasitoids [...] Read more.
The parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) is increasingly being used in integrated pest management (IPM) programs as a biological control agent in order to suppress tephritid fruit flies of economic importance. Innate and acquired behavioral responses—such as pest host fruit preference—of parasitoids can modulate their efficiency in the field and should be taken into consideration prior to parasitoid species’ selection for mass-rearing. We have assessed the influence of medfly-infested (two infestation ages, 1 and 4-d-old) and uninfested fruit species on host preference and efficiency of D. longicaudata by using a multistep assay including olfactory, laboratory and semi-field trials. We found that D. longicaudata was significantly more attracted to medfly-infested apples for both infestation ages, with the oldest being the most preferred. D. longicaudata exhibited a significant preference among the four fruits tested. The implications of these behavioral responses of D. longicaudata to medfly host fruits and infestation age are discussed in relationship to its use in IPM programs in the Mediterranean basin area. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
The Dominance Hierarchy of Wood-Eating Termites from China
Insects 2019, 10(7), 210; https://doi.org/10.3390/insects10070210
Received: 25 June 2019 / Revised: 11 July 2019 / Accepted: 12 July 2019 / Published: 18 July 2019
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Abstract
Competition is a fundamental process in ecology and helps to determine dominance hierarchies. Competition and dominance hierarchies have been little investigated in wood-eating termites, despite the necessary traits of similar resources, and showing spatial and temporal overlap. Competition and dominance between five species [...] Read more.
Competition is a fundamental process in ecology and helps to determine dominance hierarchies. Competition and dominance hierarchies have been little investigated in wood-eating termites, despite the necessary traits of similar resources, and showing spatial and temporal overlap. Competition and dominance between five species of wood-eating termites found in Huangzhou, China, was investigated in three laboratory experiments of aggression and detection, plus a year-long field survey of termite foraging activity. Dominance depended on body size, with largest species winning overwhelmingly in paired contests with equal numbers of individuals, although the advantage was reduced in paired competitions with equal biomass. The termites could detect different species from used filter papers, as larger species searched through paper used by smaller species, and smaller species avoided papers used by larger species. The largest species maintained activity all year, but in low abundance, whereas the second largest species increased activity in summer, and the smallest species increased their activity in winter. The termite species displayed a dominance hierarchy based on fighting ability, with a temporal change in foraging to avoid larger, more dominant species. The low abundance of the largest species, here Macrotermes barneyi, may be a function of human disturbance, which allows subordinate species to increase. Thus, competitive release may explain the increase in abundance of pest species, such as Coptotermes formosanus, in highly modified areas, such as urban systems. Full article
(This article belongs to the Special Issue Ecology of Termites)
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Open AccessArticle
Phylogenomic Analyses Clarify True Species within the Butterfly Genus Speyeria despite Evidence of a Recent Adaptive Radiation
Insects 2019, 10(7), 209; https://doi.org/10.3390/insects10070209
Received: 8 June 2019 / Revised: 6 July 2019 / Accepted: 12 July 2019 / Published: 17 July 2019
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Abstract
When confronted with an adaptive radiation, considerable evidence is needed to resolve the evolutionary relationships of these closely related lineages. The North American genus Speyeria is one especially challenging radiation of butterflies due to potential signs of incomplete lineage sorting, ongoing hybridization, and [...] Read more.
When confronted with an adaptive radiation, considerable evidence is needed to resolve the evolutionary relationships of these closely related lineages. The North American genus Speyeria is one especially challenging radiation of butterflies due to potential signs of incomplete lineage sorting, ongoing hybridization, and similar morphological characters between species. Previous studies have found species to be paraphyletic and have been unable to disentangle taxa, often due to a lack of data and/or incomplete sampling. As a result, Speyeria remains unresolved. To achieve phylogenetic resolution of the genus, we conducted phylogenomic and population genomic analyses of all currently recognized North American Speyeria species, as well as several subspecies, using restriction-site-associated DNA sequencing (RADseq). Together, these analyses confirm the 16 canonical species, and clarify many internal relationships. However, a few relationships within Speyeria were poorly supported depending on the evolutionary model applied. This lack of resolution among certain taxa corroborates Speyeria is experiencing an ongoing adaptive radiation, with incomplete lineage sorting and lack of postzygotic reproductive barriers contributing to hybridization and further ambiguity. Given that many Speyeria taxa are under duress from anthropogenic factors, their legal protection must be viewed cautiously and on a case by case basis in order to properly conserve the diversity being generated. Full article
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Open AccessReview
Ecological Aspects of the Vector-Borne Bacterial Disease, Citrus Greening (Huanglongbing): Dispersal and Host Use by Asian Citrus Psyllid, Diaphorina Citri Kuwayama
Insects 2019, 10(7), 208; https://doi.org/10.3390/insects10070208
Received: 31 May 2019 / Revised: 5 July 2019 / Accepted: 13 July 2019 / Published: 16 July 2019
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Abstract
Determining the influence of abiotic and biotic factors on pest dispersal behavior is a critical component of integrated pest management. The behavioral and physiological traits of movement of the Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama, has received significant attention. Field and laboratory [...] Read more.
Determining the influence of abiotic and biotic factors on pest dispersal behavior is a critical component of integrated pest management. The behavioral and physiological traits of movement of the Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama, has received significant attention. Field and laboratory experiments have explored the physiological capabilities of ACP dispersal, as well as, the abiotic and biotic drivers that initiate movement behavior. Abiotic factors such as temperature, barometric pressure, humidity, landscape, and orchard architecture, as well as, biotic factors including mating status, pathogen infection, and morphotype have been investigated in great detail. The current review focuses on dispersal of ACP with the goal of synthesizing current knowledge to suggest management tactics. Overall, vision serves as the primary modality for host finding in ACP. Current data suggest that ACP populations increase more within uniform landscapes of seedling trees, as compared to mature orchards with randomly interspersed young seedlings. The data also suggest that establishment and conservation of visual and physical barriers might be beneficial to protect orchards from ACP. Management of ACP must take into account large-area cooperation, orchard border surveillance and treatment, removal of non-crop habitat, and an understanding that immigration can occur from distances of several kilometers. Full article
Open AccessArticle
Effects of Diet Quality and Temperature on Stable Fly (Diptera: Muscidae) Development
Insects 2019, 10(7), 207; https://doi.org/10.3390/insects10070207
Received: 14 June 2019 / Revised: 2 July 2019 / Accepted: 11 July 2019 / Published: 16 July 2019
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Abstract
The effects of diet quality and temperature on the development time and size of stable flies, Stomoxys calcitrans (L.), was evaluated. Both development time and size varied relative to diet quality and temperature, and their effects were additive. Diet quality and temperature made [...] Read more.
The effects of diet quality and temperature on the development time and size of stable flies, Stomoxys calcitrans (L.), was evaluated. Both development time and size varied relative to diet quality and temperature, and their effects were additive. Diet quality and temperature made similar contributions to the variance in size whereas temperature was responsible for >97% of the variance in development time. Regression analysis predicted the shortest development time, egg to adult, to be 12.7 days at 32 °C and 70% nutrients. Egg to adult development varied curvilinearly relative to diet quality and temperature on the degree day 10 (DD10) scale taking 261 DD10 at 30 °C and 50% nutrients. The thermal threshold was 11.5 °C with a thermal constant of 248. Very few stable flies developed to adult on the poorest diet (12.5% nutrients) and adults emerged from fewer than 1% of the puparia at 35 °C. The heaviest pupae (15.4 mg) were produced with the 100% diet at 15 °C and adults had a higher probability of emerging successfully from heavier puparia. The length of the discal-medial cell of adult wings had a cubic relationship with puparia weight and peaked at 21 °C. Egg to pupariation survival was predicted to peak at 27 °C and 71% diet whereas puparia to adult survival peaked at 24 °C and 100% diet. Diet quality and temperature had no effect on sex ratio and the rate of development did not differ between the sexes. Female stable flies were ≈5% larger than males. Composite metrics for egg to pupariation and egg to adult fitness were developed. The optimum for puparia fitness was 29 °C and 78% diet quality and for adult fitness 25 °C and 83% diet quality. Diet accounted for 31% of the variance in pupal fitness and 24% of the variance in adult fitness whereas temperature accounted for 17% and 20%, respectively. Full article
(This article belongs to the Special Issue Control of House Flies and Stable Flies)
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Open AccessArticle
Temporal Dynamics of Host Use by Drosophila suzukii in California’s San Joaquin Valley: Implications for Area-Wide Pest Management
Insects 2019, 10(7), 206; https://doi.org/10.3390/insects10070206
Received: 6 June 2019 / Revised: 9 July 2019 / Accepted: 11 July 2019 / Published: 15 July 2019
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Abstract
A major challenge to the area-wide management of Drosophila suzukii is understanding the fly’s host use and temporal dynamics, which may dictate local movement patterns. We determined D. suzukii’s seasonal host use in California’s San Joaquin Valley by sampling common crop and [...] Read more.
A major challenge to the area-wide management of Drosophila suzukii is understanding the fly’s host use and temporal dynamics, which may dictate local movement patterns. We determined D. suzukii’s seasonal host use in California’s San Joaquin Valley by sampling common crop and non-crop fruits in a temporal sequence of fruit ripening. We then evaluated the suitability of selected fruits as hosts. Drosophila suzukii emerged from both intact and damaged cherries during the cooler, early season period. Fly density remained low through the hot spring–summer period and re-surged as temperatures lowered in fall when the fly did not cause damage to intact peach, nectarine, plum, pear, grape, pomegranate, apple, persimmon and citrus (in order of ripening) but did emerge from the damaged fruits of these crops. The fly also emerged from two ornamental fruits (loquats and cactus) but was not found on wild plum and two endemic wild fruits (buckthorn and bitter berry). Drosophila suzukii completed development (egg to adult) on cactus, mandarin carpel, pomegranate seed, wild plum and buckthorn at survival rates similar to cherry (51.2–68.8%), whereas it had a lower survival rate on bitter cherry (33.2%), table grape (31.5%), raisin grape (26.5%), and wine grape (4.5%). The high acidity levels of grapes negatively affected the fly’s fitness. Among 10 cherry cultivars, survival rate was not affected by sugar content, but it decreased with increasing egg density per gram of fruit. Results suggest that in California’s San Joaquin Valley, the early season crops are most vulnerable, summer fruits ripen during a period of low pest pressure, and late season fruits, when damaged, serve to sustain D. suzukii’s populations in this region. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
Population Dynamics of Spotted Wing Drosophila (Drosophila suzukii (Matsumura)) in Maine Wild Blueberry (Vaccinium angustifolium Aiton)
Insects 2019, 10(7), 205; https://doi.org/10.3390/insects10070205
Received: 1 May 2019 / Revised: 6 July 2019 / Accepted: 9 July 2019 / Published: 13 July 2019
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Abstract
A long-term investigation of D. suzukii dynamics in wild blueberry fields from 2012–2018 demonstrates relative abundance is either still increasing or exhibiting periodicity seven years after the initial invasion. Relative abundance is determined by physiological date of first detection and air temperatures the [...] Read more.
A long-term investigation of D. suzukii dynamics in wild blueberry fields from 2012–2018 demonstrates relative abundance is either still increasing or exhibiting periodicity seven years after the initial invasion. Relative abundance is determined by physiological date of first detection and air temperatures the previous winter. Date of first detection of flies does not determine date of fruit infestation. The level of fruit infestation is determined by year, fly pressure, and insecticide application frequency. Frequency of insecticide application is determined by production system. Non-crop wild fruit and predation influences fly pressure; increased wild fruit abundance results in increased fly pressure. Increased predation rate reduces fly pressure, but only at high abundance of flies, or when high levels of wild fruit are present along field edges. Male sex ratio might be declining over the seven years. Action thresholds were developed from samples of 92 fields from 2012–2017 that related cumulative adult male trap capture to the following week likelihood of fruit infestation. A two-parameter gamma density function describing this probability was used to develop a risk-based gradient action threshold system. The action thresholds were validated from 2016–2018 in 35 fields and were shown to work well in two of three years (2016 and 2017). Full article
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Open AccessArticle
Evaluation of Purdue Improved Crop Storage Triple Layer Hermetic Storage Bag against Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae)
Insects 2019, 10(7), 204; https://doi.org/10.3390/insects10070204
Received: 2 April 2019 / Revised: 25 June 2019 / Accepted: 26 June 2019 / Published: 12 July 2019
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Abstract
Hermetic technologies are being promoted in Africa as safer and more effective methods of grain storage on smallholder farms. However, farmers and policy makers lack knowledge of their efficacy in controlling major stored grain pests. An on-station study was conducted to evaluate the [...] Read more.
Hermetic technologies are being promoted in Africa as safer and more effective methods of grain storage on smallholder farms. However, farmers and policy makers lack knowledge of their efficacy in controlling major stored grain pests. An on-station study was conducted to evaluate the triple layer Purdue Improved Crop Storage (PICS) airtight bags against two major storage insect pests. Two sets each of PICS, jute and polypropylene bags were filled with 50 kg maize grain per bag. Each set was replicated four times. One set of PICS bags was each infested with 50 insects each of the larger grain borer P. truncatus and the maize weevil S. zeamais; while the other set was not. One set of jute and polypropylene woven bags was treated with a cocktail of 1.6% Pirimiphos methyl and 0.3% Permethrin, serving as positive controls; while the remaining sets with untreated maize grain formed negative controls. Gas analysis in the PICS bags followed the expected trend with oxygen levels falling sharply below 10% and carbon dioxide increasing to almost 10% after 12 weeks hence resulting in insect death. After 16 weeks, increase in oxygen levels may be attributed to perforation of the bags from outside by the P. truncatus. Results showed that PICS bags were significantly (P < 0.05) superior to treated and untreated controls of polypropylene and jute bags in suppressing insect development, maize grain damage and weight loss during storage. Weight loss in polypropylene and jute bags reached 40% and 41%, respectively, at 24 weeks after storage compared to PICS (2.4–2.9%). These results demonstrate that PICS bags can be used to store maize against P. truncatus and S. zeamais attack. Full article
(This article belongs to the Special Issue Improving Stored Product Insect Pest Management)
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Open AccessArticle
Rainfastness of Insecticides Used to Control Spotted-Wing Drosophila in Tart Cherry Production
Insects 2019, 10(7), 203; https://doi.org/10.3390/insects10070203
Received: 14 May 2019 / Revised: 8 July 2019 / Accepted: 8 July 2019 / Published: 11 July 2019
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Abstract
Tart cherry production is challenged by precipitation events that may reduce crop protection against spotted-wing drosophila (Drosophila suzukii) (SWD). Due to SWD’s devastating impacts on yield, growers are often faced with the option of insecticide reapplication. Semi-field bioassays were used to [...] Read more.
Tart cherry production is challenged by precipitation events that may reduce crop protection against spotted-wing drosophila (Drosophila suzukii) (SWD). Due to SWD’s devastating impacts on yield, growers are often faced with the option of insecticide reapplication. Semi-field bioassays were used to assess simulated rainfall effects towards adult mortality, immature survival, and residue wash-off from different plant tissues for several compounds. Tart cherry shoots were treated with 0, 12.7 or 25.4 mm of simulated rainfall and infested with SWD for 5 days. Adult mortality was recorded 1, 3, and 5 days after shoots were infested, while immature stage individuals were counted 9 days after the first infestation day. All insecticides demonstrated higher adult mortality and lower immature survival compared with the untreated control at 0 mm of rainfall. Adult mortality and immature survival caused by phosmet, zeta-cypermethrin, and spinetoram were adversely affected by simulated rainfall. In all bioassays, acetamiprid was the least affected by simulated rainfall. Residue analysis demonstrated phosmet and spinetoram residues to be the most sensitive to wash-off. This study demonstrates different rainfall effects on SWD control for several compounds. This information may provide a basis for making an informed decision on whether reapplication is required. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
Parthenogenetic Females of the Stick Insect Clitarchus hookeri Maintain Sexual Traits
Insects 2019, 10(7), 202; https://doi.org/10.3390/insects10070202
Received: 5 June 2019 / Revised: 30 June 2019 / Accepted: 3 July 2019 / Published: 10 July 2019
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Abstract
The New Zealand stick insect Clitarchus hookeri has both sexual and parthenogenetic (all-female) populations. Sexual populations exhibit a scramble competition mating system with distinctive sex roles, where females are signalers and males are searchers, which may lead to differences in the chemical and [...] Read more.
The New Zealand stick insect Clitarchus hookeri has both sexual and parthenogenetic (all-female) populations. Sexual populations exhibit a scramble competition mating system with distinctive sex roles, where females are signalers and males are searchers, which may lead to differences in the chemical and morphological traits between sexes. Evidence from a range of insect species has shown a decay of sexual traits is common in parthenogenetic lineages, especially those traits related to mate attraction and location, presumably due to their high cost. However, in some cases, sexual traits remain functional, either due to the recent evolution of the parthenogenetic lineage, low cost of maintenance, or because there might be an advantage in maintaining them. We measured morphological and chemical traits of C. hookeri to identify differences between males and females and between females from sexual and parthenogenetic populations. We also tested the ability of males to discriminate between sexual and parthenogenetic females in a laboratory bioassay. Our results show that male C. hookeri has morphological traits that facilitate mobility (smaller body with disproportionately longer legs) and mate detection (disproportionately longer antennae), and adult females release significantly higher amounts of volatile organic compounds than males when this species is sexually active, in accordance with their distinctive sex roles. Although some differences were detected between sexual and parthenogenetic females, the latter appear to maintain copulatory behaviors and chemical signaling. Males were unable to distinguish between sexual and parthenogenetic females, suggesting that there has been little decay in the sexual traits in the parthenogenetic lineage of C. hookeri. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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Open AccessArticle
Modeling Potential Habitat for Amblyomma Tick Species in California
Insects 2019, 10(7), 201; https://doi.org/10.3390/insects10070201
Received: 20 April 2019 / Revised: 21 June 2019 / Accepted: 2 July 2019 / Published: 8 July 2019
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Abstract
The Amblyomma genus of ticks comprises species that are aggressive human biters and vectors of pathogens. Numerous species in the genus are undergoing rapid range expansion. Amblyomma ticks have occasionally been introduced into California, but as yet, no established populations have been reported [...] Read more.
The Amblyomma genus of ticks comprises species that are aggressive human biters and vectors of pathogens. Numerous species in the genus are undergoing rapid range expansion. Amblyomma ticks have occasionally been introduced into California, but as yet, no established populations have been reported in the state. Because California has high ecological diversity and is a transport hub for potentially parasitized humans and animals, the risk of future Amblyomma establishment may be high. We used ecological niche modeling to predict areas in California suitable for four tick species that pose high risk to humans: Amblyomma americanum, Amblyomma maculatum, Amblyomma cajennense and Amblyomma mixtum. We collected presence data in the Americas for each species from the published literature and online databases. Twenty-three climatic and ecological variables were used in a MaxEnt algorithm to predict the distribution of each species. The minimum temperature of the coldest month was an important predictor for all four species due to high mortality of Amblyomma at low temperatures. Areas in California appear to be ecologically suitable for A. americanum, A. maculatum, and A. cajennense, but not A. mixtum. These findings could inform targeted surveillance prior to an invasion event, to allow mitigation actions to be quickly implemented. Full article
(This article belongs to the Special Issue Tick Surveillance and Tick-borne Diseases)
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Open AccessArticle
Olfactory Preference of Drosophila suzukii Shifts between Fruit and Fermentation Cues over the Season: Effects of Physiological Status
Insects 2019, 10(7), 200; https://doi.org/10.3390/insects10070200
Received: 6 June 2019 / Revised: 28 June 2019 / Accepted: 4 July 2019 / Published: 6 July 2019
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Abstract
Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV [...] Read more.
Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV baited traps indeed provide a distorted image of the D. suzukii population dynamics as it is possible to capture higher numbers during this “low capture period” with synthetic lures. It was hypothesised that the preference of D. suzukii populations for fermentation cues like ACV is most pronounced during autumn, winter and spring, while the flies prefer fresh fruit cues during summer and that this seasonal preference is related to the changing physiology of the flies over the season. To test this hypothesis, the preference between fermentation cues (ACV) and host fruits (strawberries) and the effect of physiology (sex, seasonal morphology and feeding, mating and reproductive status) was investigated both in olfactometer laboratory experiments and a year-round field preference experiment. In olfactometer experiments we demonstrated that protein deprived females, virgin females with a full complement of unfertilised eggs and males show a strong preference for fermentation cues while fully fed reproductive summer morph females generally prefer fruit cues. These findings indicate that D. suzukii is attracted to fermentation volatiles in search of (protein-rich) food and to fruit volatiles in search of oviposition substrates. Winter morph and starved females displayed indiscriminating olfactory behaviour. In the field preference experiment, the hypothesised seasonal shift between fermentation and fruit cues was confirmed. This shift appeared to be highly temperature-related and was similarly observed for summer and winter morphs. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
Comparative Morphological, Ultrastructural, and Molecular Studies of Four Cicadinae Species Using Exuvial Legs
Insects 2019, 10(7), 199; https://doi.org/10.3390/insects10070199
Received: 29 May 2019 / Revised: 24 June 2019 / Accepted: 3 July 2019 / Published: 6 July 2019
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Abstract
Previous studies have suggested that exuviae can be used for the identification of cicada species, but the precise characteristics that differ among species have not been determined. Thus, we performed the first comparative analyses of the leg morphology, ultrastructure, and mitochondrial DNA sequences [...] Read more.
Previous studies have suggested that exuviae can be used for the identification of cicada species, but the precise characteristics that differ among species have not been determined. Thus, we performed the first comparative analyses of the leg morphology, ultrastructure, and mitochondrial DNA sequences of exuviae of four dominant cicada species in Korea, Hyalessa maculaticollis (Motschulsky, 1866), Meimuna opalifera (Walker, 1850), Platypleura kaempferi (Fabricius, 1794) and Cryptotympana atrata (Fabricius, 1775), the source of Cicadidae Periostracum, a well-known traditional medicine. A morphological analysis revealed that the profemur length, femoral tooth angle, and distance between the intermediate and last tooth of the femoral comb are useful characteristics for identification. We also evaluated the usefulness of the size, degree of reflex, and number of spines on the mid-legs and hind legs as diagnostic features. An ultrastructural study showed that Meimuna opalifera has a unique surface pattern on the legs. The sequences obtained using exuviae were identical to previously obtained sequences for adult tissues. Moreover, in a phylogenetic analysis using CO1 sequences, each species formed a monophyletic cluster with high bootstrap support. Accordingly, multiple methodological approaches using exuviae might provide highly reliable identification tools. The integrative data provide useful characteristics for the exuviae-based identification of closely related species and for further taxonomic and systematic studies of Cicadinae. Full article
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Open AccessArticle
Susceptibility of Field Populations of Eggplant Fruit and Shoot Borer (Leucinodes orbonalis Guenée) to Cry1Ac, the Protein Expressed in Bt Eggplant (Solanum melongena L.) in Bangladesh
Insects 2019, 10(7), 198; https://doi.org/10.3390/insects10070198
Received: 15 April 2019 / Revised: 30 May 2019 / Accepted: 2 July 2019 / Published: 5 July 2019
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Abstract
Eggplant (Solanum melongena Linn.), or brinjal, was engineered to express an insecticidal protein (Cry1Ac) from Bacillus thuringiensis (Bt) and commercialized in Bangladesh on a limited basis in 2014. As part of an insect resistance management strategy, studies were conducted to determine the [...] Read more.
Eggplant (Solanum melongena Linn.), or brinjal, was engineered to express an insecticidal protein (Cry1Ac) from Bacillus thuringiensis (Bt) and commercialized in Bangladesh on a limited basis in 2014. As part of an insect resistance management strategy, studies were conducted to determine the susceptibility of the targeted insect pest, the eggplant fruit and shoot borer, Leucinodes orbonalis (Guenée), to Cry1Ac using a diet-incorporation bioassay method. Eighteen populations of L. orbonalis were collected from the main brinjal growing areas in 17 districts of Bangladesh during 2018–2019 and assayed. Larvae from each population were reared to adults and allowed to mate. Eggs from the matings were allowed to hatch, and neonates were used for bioassays. Bioassays were performed with different concentrations of Cry1Ac and an untreated control. Median lethal concentrations (LC50) ranged between 0.035 and 0.358 ppm and molt inhibitory concentration (MIC50) values ranged from 0.008 to 0.181 ppm. Variation in susceptibility among field populations was 10.22-fold for LC50 and 22.63-fold for MIC50. These results were compared to values from 73 populations in India. Overall, the results showed similar natural variation and suggest that these Bangladeshi values can be used as benchmarks for resistance monitoring as Bt brinjal becomes more widely adopted in Bangladesh. Full article
Open AccessArticle
Changing Host Plants Causes Structural Differences in the Parasitoid Complex of the Monophagous Moth Yponomeuta evonymella, but Does Not Improve Survival Rate
Insects 2019, 10(7), 197; https://doi.org/10.3390/insects10070197
Received: 13 April 2019 / Revised: 19 June 2019 / Accepted: 3 July 2019 / Published: 4 July 2019
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Abstract
Recently in Poland, cases of host expansion have frequently been observed in the typically monophagous bird-cherry ermine moth (Yponomeuta evonymella), which has moved from its native host plant, bird cherry (Prunus padus), to a new, widely distributed plant that [...] Read more.
Recently in Poland, cases of host expansion have frequently been observed in the typically monophagous bird-cherry ermine moth (Yponomeuta evonymella), which has moved from its native host plant, bird cherry (Prunus padus), to a new, widely distributed plant that is invasive in Europe, black cherry (P. serotina). We attempted to verify the reasons behind this host change in the context of the enemy-free space hypothesis by focusing on parasitoids attacking larval Y. evonymella on one of three host plant variants: The primary host, P. padus; initially P. padus and later P. serotina (P. padus/P. serotina); or the new host, P. serotina. This experiment investigated if changing the host plant could be beneficial to Y. evonymella in terms of escaping from harmful parasitoids and improving survival rate. We identified nine species of parasitoids that attack larval Y. evonymella, and we found that the number of parasitoid species showed a downward trend from the primary host plant to the P. padus/P. serotina combination to the new host plant alone. We observed a significant difference among variants in relation to the percentage of cocoons killed by specific parasitoids, but no effects of non-specific parasitoids or other factors. Total mortality did not significantly differ (ca. 37%) among larval rearing variants. Changing the host plant caused differences in the structure of the parasitoid complex of Y. evonymella but did not improve its survival rate. This study does not indicate that the host expansion of Y. evonymella is associated with the enemy-free space hypothesis; we therefore discuss alternative scenarios that may be more likely. Full article
(This article belongs to the Special Issue Impact of Introduced Plants on Insects)
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Open AccessArticle
Insecticide Control of Drosophila suzukii in Commercial Sweet Cherry Crops under Cladding
Insects 2019, 10(7), 196; https://doi.org/10.3390/insects10070196
Received: 31 May 2019 / Revised: 27 June 2019 / Accepted: 2 July 2019 / Published: 4 July 2019
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Abstract
Drosophila suzukii Matsumura is a damaging invasive pest of sweet cherry. Using a series of laboratory leaf contact assays, semi-field, and orchard spray programs we aimed to determine the impact of insecticide programs on D. suzukii adult mortality and oviposition in cladding-protected sweet [...] Read more.
Drosophila suzukii Matsumura is a damaging invasive pest of sweet cherry. Using a series of laboratory leaf contact assays, semi-field, and orchard spray programs we aimed to determine the impact of insecticide programs on D. suzukii adult mortality and oviposition in cladding-protected sweet cherry crops. Tests included assessing adult D. suzukii mortality after contact with leaves sprayed either one or two weeks previously and emergence of adults from fruits. Spinosad, lambda-cyhalothrin, acetamiprid, lime, pyrethrin, deltamethrin, and cyantraniliprole all reduced fruit damage up to day 7 after application. Of these active ingredients, only spinosad, lambda-cyhalothrin, and cyantraniliprole gave satisfactory control up to 14 days. There was no significant difference in D. suzukii mortality when exposed to leaves treated either one or two weeks previously with an application of either spinosad, cyantraniliprole, or lambda-cyhalothrin; however, mortality was significantly higher than D. suzukii in contact with untreated leaves. In eight commercial orchards, fortnightly spray applications including spinosad, cyantraniliprole, and lambda-cyhalothrin gave effective control of D. suzukii until harvest with very few damaged fruits. These experiments demonstrate that currently approved plant protection products, applied to sweet cherry under protection, give at least two weeks protection from D. suzukii. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessArticle
Fall Armyworm, Spodoptera frugiperda Infestations in East Africa: Assessment of Damage and Parasitism
Insects 2019, 10(7), 195; https://doi.org/10.3390/insects10070195
Received: 24 May 2019 / Revised: 19 June 2019 / Accepted: 22 June 2019 / Published: 3 July 2019
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Abstract
The fall armyworm (FAW), Spodoptera frugiperda, threatens maize production in Africa. A survey was conducted to determine the distribution of FAW and its natural enemies and damage severity in Ethiopia, Kenya and Tanzania in 2017 and 2018. A total of 287 smallholder [...] Read more.
The fall armyworm (FAW), Spodoptera frugiperda, threatens maize production in Africa. A survey was conducted to determine the distribution of FAW and its natural enemies and damage severity in Ethiopia, Kenya and Tanzania in 2017 and 2018. A total of 287 smallholder maize farms (holding smaller than 2 hectares of land) were randomly selected and surveyed. FAW is widely distributed in the three countries and the percent of infested maize fields ranged from 33% to 100% in Ethiopia, 93% to 100% in Tanzania and 100% in Kenya in 2017, whereas they ranged from 80% to 100% and 82.2% to 100% in Ethiopia and Kenya, respectively, in 2018. The percent of FAW infestation of plants in the surveyed fields ranged from 5% to 100%. In 2017, the leaf damage score of the average of the fields ranged from 1.8 to 7 (9 = highest level of damage), while 2018, it ranged from 1.9 to 6.8. In 2017, five different species of parasitoids were recovered from FAW eggs and larvae. Cotesia icipe (Hymenoptera: Braconidae) was the main parasitoid recorded in Ethiopia, with a percent parasitism rate of 37.6%. Chelonus curvimaculatus Cameron (Hymenoptera: Braconidae) was the only egg-larval parasitoid recorded in Kenya and had a 4.8% parasitism rate. In 2018, six species of egg and larval parasitoids were recovered with C. icipe being the dominant larval parasitoid, with percentage parasitism ranging from 16% to 42% in the three surveyed countries. In Kenya, Telenomus remus (Hymenoptera: Scelionidae) was the dominant egg parasitoid, causing up to 69.3% egg parasitism as compared to only 4% by C. curvimaculatus. Although FAW has rapidly spread throughout these three countries, we were encouraged to see a reasonable level of biological control in place. Augmentative biological control can be implemented to suppress FAW in East Africa. Full article
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Open AccessEditorial
Mechanisms Underlying the Transmission of Insect Pathogens
Insects 2019, 10(7), 194; https://doi.org/10.3390/insects10070194
Received: 22 June 2019 / Revised: 28 June 2019 / Accepted: 28 June 2019 / Published: 2 July 2019
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Abstract
In this special issue the focus is on the factors and (molecular) mechanisms that determine the transmission efficiency of a variety of insect pathogens in a number of insect hosts. In this editorial, we summarize the main findings of the twelve papers in [...] Read more.
In this special issue the focus is on the factors and (molecular) mechanisms that determine the transmission efficiency of a variety of insect pathogens in a number of insect hosts. In this editorial, we summarize the main findings of the twelve papers in this special issue and conclude that much more needs to be learned for an in-depth understanding of pathogen transmission in field and cultured insect populations. Analyses of mutual interactions between pathogens or between endosymbionts and pathogens, aspects rather under-represented in the scientific literature, are described in a number of contributions to this special issue. Full article
(This article belongs to the Special Issue Mechanisms Underlying Transmission of Insect Pathogens)
Open AccessArticle
Season Long Pest Management Efficacy and Spray Characteristics of a Solid Set Canopy Delivery System in High Density Apples
Insects 2019, 10(7), 193; https://doi.org/10.3390/insects10070193
Received: 29 May 2019 / Revised: 21 June 2019 / Accepted: 25 June 2019 / Published: 29 June 2019
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Abstract
Solid set canopy delivery systems (SSCDS) are a novel foliar agrochemical delivery system designed as an alternative for airblast sprayers in high density fruit production. This study tested the pest management potential, coverage, and chemical deposition of an SSCDS using commercially available microsprinkler [...] Read more.
Solid set canopy delivery systems (SSCDS) are a novel foliar agrochemical delivery system designed as an alternative for airblast sprayers in high density fruit production. This study tested the pest management potential, coverage, and chemical deposition of an SSCDS using commercially available microsprinkler components over the course of a growing season. Spray coverage and deposition for a representative airblast sprayer and SSCDS were evaluated using water sensitive paper and tartrazine dye, respectively. Foliar sprays for pest suppression were applied through both systems, and damage assessments were taken at the midpoint and end of the growing season. SSCDS sprays demonstrated similar levels of coverage on the adaxial leaf surface as airblast sprays, but significantly lower coverage on the abaxial surface. However, mean levels of foliar chemical deposition was generally higher in the SSCDS. Evaluations found minimal arthropod and fungal damage in both airblast and SSCDS treated plots compared to untreated trees. The SSCDS was shown to be a viable alternative to the airblast, with inherent advantages such as rapid application time and improved worker safety. Furthermore, higher deposition on SSCDS treated foliage supports the hypothesis that SSCDS provide a higher droplet capture rate in the canopy, with less off-target loss and drift than airblast sprayers. Full article
(This article belongs to the Special Issue Pest Control in Fruit Trees)
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Open AccessCommunication
Pest Control Potential of Social Wasps in Small Farms and Urban Gardens
Insects 2019, 10(7), 192; https://doi.org/10.3390/insects10070192
Received: 30 April 2019 / Revised: 20 June 2019 / Accepted: 21 June 2019 / Published: 28 June 2019
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Abstract
In environments undergoing constant transformation due to human action, such as deforestation and urbanization, the emergence of pests has become a challenge for agriculture and human welfare. In Brazil, over a thousand tonnes of pesticides are used annually, causing serious environmental damage such [...] Read more.
In environments undergoing constant transformation due to human action, such as deforestation and urbanization, the emergence of pests has become a challenge for agriculture and human welfare. In Brazil, over a thousand tonnes of pesticides are used annually, causing serious environmental damage such as the decline of insect populations. It is necessary to search for control alternatives in order to reduce the environmental impact caused by insecticides. This review aims to describe the use of social wasps as agents of biological control, focusing on the perspectives of their use in small farms and urban gardens, and to discuss the benefits of using this method. Studies have shown that 90–95% of the prey captured by wasps in small crops is made of leaf-eating caterpillars. In urban gardens, wasps diversify their prey, among which potential disease vectors, such as dipterans, stand out. We outline techniques for managing social wasp colonies in small farm and urban garden settings, including the use of artificial shelters. Among the advantages of using wasps as control agents, we highlight the practicality of the method, the low operational cost, the absence of prey resistance and the decrease of the use of insecticides. Full article
(This article belongs to the Special Issue Urban Small Farms and Gardens Pest Management)
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Open AccessArticle
Carry-Over Niches for Lepidopteran Maize Stemborers and Associated Parasitoids during Non-Cropping Season
Insects 2019, 10(7), 191; https://doi.org/10.3390/insects10070191
Received: 8 April 2019 / Revised: 30 May 2019 / Accepted: 5 June 2019 / Published: 28 June 2019
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Abstract
Sources of infestation are the key elements to be considered in the development of habitat management techniques for the control of maize stemborers. Several wild plants, grasses mostly, have been identified that serve as hosts for stemborers and their parasitoids during the off-season [...] Read more.
Sources of infestation are the key elements to be considered in the development of habitat management techniques for the control of maize stemborers. Several wild plants, grasses mostly, have been identified that serve as hosts for stemborers and their parasitoids during the off-season when maize is not present in the field. However, their abundance is much lower in wild plants compared to cultivated fields. Thus, the role of wild plants as a reservoir for cereal stemborers and their parasitoids is still controversial, particularly in agro-ecosystems with reduced wild habitat. We studied the occurrence of different maize stemborers and associated parasitoids in maize stem residues and wild grasses during non-cropping seasons as potential carry-over populations to subsequent early season maize plants. Surveys were conducted in the central region of Kenya during long and short dry seasons in maize residues and wild grasses as well as during the two rainy seasons in maize plants at earlier and late whorl stages during the years of 2017 and 2018. Wild habitat had a higher species diversity than maize residues habitat, but maize residues had a higher abundance of maize stemborer species, such as Busseola fusca, Sesamia calamistis, and Chilo partellus, and of associated parasitoid species (i.e., Cotesia flavipes and Cotesia sesamiae) than wild plants. Our surveys, complemented by field parasitoid releases of C. flavipes and C. sesamiae, indicated that maize residues constitute a better refugia reservoir not only of the maize stemborers but also of C. flavipes and C. sesamiae during non-cropping seasons as compared to wild plants and, thus, might constitute in this region the main source of both stemborers and C. flavipes/C. sesamiae carry-over in maize plants during the subsequent cropping season. Thus, systematic destruction of maize residues would not help the biological control of lepidopteran stemborers. This is particularly true in areas with reduced wild habitat. Full article
(This article belongs to the Special Issue Pest Management in Sustainable Farming Systems)
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Open AccessArticle
Modeling the Distribution of Medically Important Tick Species in Florida
Insects 2019, 10(7), 190; https://doi.org/10.3390/insects10070190
Received: 15 April 2019 / Revised: 18 May 2019 / Accepted: 20 June 2019 / Published: 28 June 2019
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Abstract
The lone star (Amblyomma americanum), black-legged (Ixodes scapularis) and American dog ticks (Dermacentor variabilis) are species of great public health importance as they are competent vectors of several notable pathogens. While the regional distributions of these species [...] Read more.
The lone star (Amblyomma americanum), black-legged (Ixodes scapularis) and American dog ticks (Dermacentor variabilis) are species of great public health importance as they are competent vectors of several notable pathogens. While the regional distributions of these species are well characterized, more localized distribution estimates are sparse. We used records of field collected ticks and an ensemble modeling approach to predict habitat suitability for each of these species in Florida. Environmental variables capturing climatic extremes were common contributors to habitat suitability. Most frequently, annual precipitation (Bio12), mean temperature of the driest quarter (Bio9), minimum temperature of the coldest month (Bio6), and mean Normalized Difference Vegetation Index (NDVI) were included in the final models for each species. Agreement between the modeling algorithms used in this study was high and indicated the distribution of suitable habitat for all three species was reduced at lower latitudes. These findings are important for raising awareness of the potential for tick-borne pathogens in Florida. Full article
(This article belongs to the Special Issue Tick Surveillance and Tick-borne Diseases)
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Open AccessArticle
Influence of Insect Growth Regulators on Stephanitis pyrioides (Hemiptera: Tingidae) Eggs and Nymphs
Insects 2019, 10(7), 189; https://doi.org/10.3390/insects10070189
Received: 3 June 2019 / Revised: 24 June 2019 / Accepted: 26 June 2019 / Published: 28 June 2019
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Abstract
The azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae), is an important insect pest of azaleas (Rhododendron L. spp.) in the USA. Stephanitis pyrioides feeds on azalea foliage and causes extensive chlorosis, which reduces the aesthetic value and marketability of these plants. [...] Read more.
The azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae), is an important insect pest of azaleas (Rhododendron L. spp.) in the USA. Stephanitis pyrioides feeds on azalea foliage and causes extensive chlorosis, which reduces the aesthetic value and marketability of these plants. Because the use of neonicotinoid insecticides has been dramatically reduced or discontinued, growers and landscape managers are seeking alternative tools or strategies to control this insect. Although insect growth regulators (IGRs) are known for their activity against immature insect stages, their activity against egg hatching has not been addressed thoroughly, specifically against S. pyrioides. Thus, a series of experiments was conducted to understand the ovicidal activity of IGRs using novaluron, azadirachtin, pyriproxyfen, and buprofezin against S. pyrioides. The number of newly emerged young instars was significantly lower when leaves implanted with eggs were sprayed on both sides with novaluron, azadirachtin, and buprofezin compared to nontreated and pyriproxyfen treatments. When IGRs plus adjuvant were applied to the adaxial surface of the leaves, the densities of the newly emerged nymphs were significantly lower under the novaluron treatment compared to the nontreated leaves. However, there was no significant difference in the number of nymphs that emerged in the absence of adjuvant. Furthermore, close monitoring revealed reduced levels of egg hatching in the presence of adjuvant with novaluron compared to its absence. The data show that the survival of S. pyrioides first instars was not affected by exposure to dried IGR residues. Full article
(This article belongs to the Special Issue Urban Small Farms and Gardens Pest Management)
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