Host range and genetic strains of leafminer flies (Diptera: Agromyzidae) in eastern Brazil reveal a new divergent clade of Liriomyza sativae

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Interspecific and intraspecific differences in two Liriomyzaleafminer species in California

In recent years, the pest status of Liriomyza trifolii (Burgess) and L. huidobrensis (Blanchard) (Diptera: Agromyzidae) has changed in California, as well as other areas of the world. In California, L. huidobrensis has become the predominant Liriomyza species in valleys along the central coast, while L. trifolii remains the predominant species in southern California. To investigate possible reasons for this change in status, differences in host plant use and reproductive success of intraspecific populations were examined for Liriomyza trifolii and L. huidobrensis from both central and southern California. The southern L. trifolii fed, oviposited and reproduced successfully on all five hosts tested, but the central population fed significantly less on all hosts and was restricted to reproducing on pepper only. With the exception of pepper, southern L. trifolii had significantly greater larval survival on all hosts than central L. trifolii. In contrast, the central L. huidobrensis population had greater reproductive success than the southern population of that species on all hosts plants tested. However, pepper was not a suitable host for either L. huidobrensis population. Both species showed positive assortative mating, with homotypic mating occurring more frequently than heterotypic mating; however, the difference between L. trifolii populations was much more pronounced than between L. huidobrensis populations. These data indicate that central and southern California populations of each species are distinct biotypes. Furthermore when coupled with previous genetic data, our results suggest the possible existence of cryptic species within L. trifolii.     

Mass production of Diglyphus isaea (Hymenoptera: Eulophidae), a biological control agent of a Korean population of potato leaf miner Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae)

The potato leaf miner, Liriomyza huidobrensis (Blanchard), is an important pest of potato throughout the world, including Korea. A method was developed for mass rearing the parasitoid Diglyphus isaea (Walker) using faba bean, Vicia faba L. (Fabaceae), as the host‐plant and L. huidobrensis as the insect host. Faba bean plants were planted in pots and maintained in a greenhouse for about 15 d. Pots were then exposed to adult leaf miners in oviposition cages for 4 h. Plants containing late second to early third instar larvae were exposed to adult D. isaea in parasitoid cages for 24 h. The leaf area per pot after 15 d was 597.9 cm², which produced 103.33 larvae per pot. The number of adult parasitoids emerging per pot was 72.5; about 41% of these were female. The daily cost of parasitoid production was USD20.95 per 1000 individual parasitoids. The methodology developed for D. isaea could be used to rear other ectoparasitoids such as Hemiptarsenus spp. and Pnigalio sp. with different insect hosts like L. trifolii. This is why this mass‐rearing information is important for securing test insect materials for ecological and biological study of Liriomyza species, and also for developing a biological control for Liriomyza species other than L. huidobrensis by mass production of associated natural enemies. We are facing rapid agro‐ecosystem changes including pest systems. Continuous monitoring of Liriomyza in solanaceous crops is needed.     

Liriomyza huidobrensis in Yunnan, China: current distribution and genetic structure of a recently established population

Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) is a very serious and economically important pest around the world. Liriomyza huidobrensis in China was first reported from Kunming of Yunnan province in 1993. We report here that this pest has recently expanded its distribution, along with a host plant range extension and population explosion. The mitochondrial cytochrome oxidase II gene was sequenced for eight populations from Yunnan. All individuals were identical: no genetic variation was observed between populations either from different geographical localities or from different host plants. The phylogenetic analysis shows that the Yunnan population is grouped into the South American clade, which also includes other recently introduced Asian populations. Together with ecological data and colonization history of this pest, our results suggest that Yunnan population might have an ultimate, albeit not immediate, origin from South American populations.     

Identifying factors determining the altitudinal distribution of the invasive pest leafminers Liriomyza huidobrensis and Liriomyza sativae

Abiotic and biotic factors that change with altitude can influence the distribution of herbivorous insects. We examined factors influencing the distribution of the generalist leafminers Liriomyza sativae Blanchard and Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae), two pests of agricultural crops, in the tropical Dieng mountainous area of Central Java, Indonesia. Liriomyza huidobrensis predominated at altitudes above 700 m a.s.l. and was the only species collected above 1 400 m a.s.l. In contrast, L. sativae predominated below 600 m a.s.l. and was not found above 1 200 m where the average temperature was 20.7 °C. Parasitoid diversity decreased with altitude, but parasitism did not change. The distribution of neither species was affected by parasitoids; L. huidobrensis predominant at high altitudes was preferred by Opius parasitoids common at these altitudes. Intra‐ and interspecific competition was detected in laboratory experiments where larval density was high, but led to coexistence rather than species displacement. No competition was detected in a field experiment when larval density was low. However, L. sativae failed to reproduce at the highest altitude, whereas L. huidobrensis established at all altitudes. Host composition varied with altitude and one host (faba beans) preferred by L. huidobrensis was common at high altitudes. By relating published data on the performance of the leafminer species to altitudinal temperature changes, we were partly successful in predicting the altitude at which the dominant species switched. Temperature plays an overriding influence on the altitudinal distribution of leafminers.     

Time-concentration interplay in insecticide resistance among populations of the Neotropical coffee leaf miner,Leucoptera coffeella

1. Leucoptera coffeella is one of the main coffee pests in the Neotropical region and particularly important in crops cultivated under full sun, as in Brazil. The intensive use of insecticides in the last two decades, including molecules of recent use such as chlorantranilprole, has not been successful in suppressing this pest species.
2. Thus, study aimed to detect insecticide resistance and determine the levels of resistance to commercial formulations of the insecticides chlorantraniliprole, chlorpyrifos and thiamethoxam in populations of L. coffeella from Arabica coffee fields in western and the highlands of the state Bahia (Brazil). Furthermore, as the expression of insecticide toxicity varies with the length of exposure and the compound concentration, what is frequently neglected, these two variables were considered while determining the levels of resistance in nine populations.
3. Moderate levels of resistance were detected to chlorantranilprole in two populations, whereas the others exhibited low levels of resistance. All populations were resistant to thiamethoxam ranging from low to moderate levels. Low levels of resistance to chlorpyrifos were detected in all populations from western, but none from highlands region.
4. The western presents a more concerning scenario of insecticide resistance the L. coffeella, but the phenomenon requires attention in both regions.

     

Primer design for identifying economically important Liriomyza species (Diptera: Agromyzidae) by multiplex PCR

Leafminer flies, especially, Liriomyza huidobrensis, Liriomyza sativae and Liriomyza trifolii, are quarantine species in many countries. Their morphological similarity makes identification difficult. To develop a rapid, reliable, sensitive and simple molecular identification method using multiplex PCR, we newly sequenced the mitochondrial cytochrome oxidase I (COI) genes of Liriomyza bryoniae, Liriomyza chinensis, L. huidobrensis, L. sativae, L. trifolii, Chromatomyia horticola and four parasitoid species. We aligned them with all the COI sequences of the leafminer flies found in the international DNA nucleotide sequence databases (DDBJ/EMBL/GenBank). We then designed species‐specific primers to allow us to differentiate between L. bryoniae, L. chinensis, L. huidobrensis, L. sativae, and L. trifolii.     

Insecticide toxicity and walking response of three pirate bug predators of the tomato leaf miner Tuta absoluta

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Climate change scenarios and models yield conflicting predictions about the future risk of an invasive species in North America

• 1 The pea leafminer Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae) is an invasive species in North America and a serious economic pest on a wide variety of crops. We developed a bioclimatic envelope model (BEM) for this species and examined the envelope's potential location in North America under various future climates.
• 2 We compared the future bioclimatic envelopes for L. huidobrensis using either simple scenarios comprising uniform changes in temperature/precipitation or climate projections from general circulation models (GCMs). Our simple scenarios were: (i) an increase of 0.1°C per degree in latitude with a 20% increase in summer precipitation and a 20% decrease in winter precipitation and (ii) an overall increase of 3°C everywhere, also with the same changes in precipitation. For GCM‐modelled climate change, we used the Canadian Centre for Climate Modelling and Analysis GCM (CGCM2) and the Hadley Centre climate model (HadCM3), each in combination with two scenarios from the Special Report on Emissions Scenarios (A2 and B2).
• 3 The BEM results using the simple scenarios were more similar to each other than to the results obtained using GCM projections. The results were also qualitatively different (i.e. spatially different and divergent) depending on which GCM‐scenario combination was used.
• 4 This modelling exercise illustrates that: (i) results using first approximation simple climate change scenarios can give predictions very different from those that use GCM‐modelled climate projections (comprising a result that has worrying implications for empirical impact research) and that (ii) different GCM‐models using the same scenario can give very different results (implying strong model dependency in projected biological impacts).

     

The compatibility of the entomopathogenic nematode,Steinernema feltiae, and chemical insecticidesfor the control of the South American leafminer, Liriomyza huidobrensis

The compatibility of infectivejuveniles (IJs) of entomopathogenic nematodes, Steinernema feltiae, and chemical insecticides tocontrol larval stages of the South American leafminer,Liriomyza huidobrensis, was investigated.Initially the effect of direct IJ exposure to 5insecticides (abamectin, deltamethrin, dimethoate,heptenophos and trichlorfon) for 24 hours was testedagainst Galleria mellonella in a standard sandtube bioassay. Trichlorfon and dimethoate did notreduce the nematodes ability to locate and infect G. mellonella larvae to an unacceptable level. However,nematode infectivity was significantly reducedfollowing exposure to abamectin, deltamethrin andheptenophos. Secondly, IJ infectivity for L.huidobrensis in the presence of dry pesticideresidues on foliage was tested. No significantdetrimental effects on the level of control of L. huidobrensis was recorded when compared with theeffect of nematodes applied to residue free foliage.The integration of these agents into a pest managementprogramme is discussed.     

Optimizing biocontrol using phenological day degree models: the European earwig in pipfruit orchards

• 1 Phenological day degree models are often used as warning systems for the emergence of arthropod pests in agricultural crops or the occurrence of natural enemies of the pest species. In the present study, we report on a case study of the European earwig Forficula auricularia L., which is an important natural enemy in pipfruit orchards, and describe how such a day degree model can be used to avoid negative effects of crucial orchard management, such as spray applications and soil tillage. A precise timing of these interventions in relation to the phenology of natural enemies will enhance biocontrol.
• 2 Earwig population dynamics are characterized by single‐ and double‐brood populations, each with specific biological characteristics.
• 3 A day degree model capable of predicting the phenology of local earwig populations of both population types was developed. The model was checked for accuracy by comparing the first field observation dates of various life stages with predicted values using temperature data from the nearest weather station. In addition, variation in development time was assessed using field data.
• 4 The model was able to make predictions on a global scale. Although single‐ and double‐brood populations differ in phenology, the predictions of first appearance dates were similar. Variation in development time showed that single‐brood populations were more synchronized.
• 5 Our phenological model provides an accurate tool for predicting and simulating earwig population dynamics, as well as for enhancing the biocontrol of pests in pipfruit orchards.

     

Effect of <Emphasis Type="Italic">Liriomyza huidobrensis</Emphasis> (Diptera: Agromyzidae) density on foliar leaf damage and yield loss in potato

Liriomyza huidobrensis (Blanchard) is a key pest of potatoes worldwide and an emerging pest of potatoes in Korea. To understand the nature of the damage caused by this pest and the potential for yield loss, potato (Solanum tuberosum), cv. Superior was exposed to different pest infestation levels (0, 2, 5, 10, 20, and 50 individuals/cage) for 27 days and the relationship between pest density and crop damage assessment was determined using both laboratory cage studies and field cages. Leaf stippling, number of mines per leaf, % leaf area mined, and yield loss varied significantly with infestation density level in both the laboratory and field. The greatest leaf area mined and yield loss were associated with the 20- and 50-individual infestation rates in both the laboratory and field. There was a significant relationship between female choice (as shown by stippling, caused by adult feeding and oviposition) and larval performance (as reflected by the number of mines, damaged leaf area, and yield loss). It is important to understand the nature of the damage caused by L. huidobrensis and to determine its economic threshold for potato in order to optimize the management of this leafminer and minimize management costs.     

Can natural enemies of current insect pests provide biotic resistance to future pests?

1. Economic pests jeopardize agricultural production worldwide. Classical biological control, comprising the import of exotic natural enemies to control target pest populations, has a successful history in many countries. However, little is known about how these natural enemies contribute to the suppression of pests that are yet to arrive. Biotic resistance theory, though, posits that communities resist species invasions as a result of natural enemies.
2. We assessed the potential of the resident exotic parasitoid wasp fauna in New Zealand (intentionally‐introduced biological control agents and unintentionally‐introduced species) to provide biotic resistance against possible future pests. A dataset was generated containing resident exotic parasitoid species (Ichneumonoidea: Braconidae; Ichneumonidae) in New Zealand, as well as their known global host ranges and the pest status of host species, to infer the potential for biotic resistance.
3. The known exotic ichneumonoid fauna in New Zealand comprises 65 species. These species associate with 107 host species in New Zealand, of which 54 species are pests. However, the current exotic species could potentially suppress 442 pest species not yet occurring in New Zealand.
4. This approach could be used to inform pest management programmes worldwide. Future research should consider how biotic resistance from the established parasitoid fauna can be used to inform specific decisions with respect to classical biological control.

     

The influence of leaf traits and deficit irrigation on insect communities in mature green tomato production

1. Drought affects many agriculturally important areas, hampering the cultivation of water intensive crops such as tomatoes.
2. Unlike processing tomatoes, deficit irrigation of fresh market tomatoes is not currently practiced. Deficit irrigation could have negative trade‐offs for yield and pest populations by changing plant nutritional values and the microenvironment.
3. The present study compared crop response and insect populations at two field locations: an on‐farm trial with 0%, 15% and 30% water deficit treatments, and a research station trial with 0%, 10%, 20% and 30% water deficit treatments.
4. At the on‐farm trial, water deficits of 30% affected fruit yield, leaf relative water content (RWC) and leaf δ¹³C, whereas, in the research station trial, water deficits only affected leaf RWC. Treatments did not change the abundance of any insect groups.
5. Sap‐feeding insects such as silverleaf whitefly (Bemisia tabaci) increased with plant traits indicating hydration such as canopy temperature depression (CTD) and RWC. Furthermore, CTD influenced the composition of insect communities.
6. Sap‐feeding insect abundance may vary with traits indicating hydration because of turgor pressure required for feeding, as well as a more suitable microenvironment.

     

Effects of Melia azedarach, (Meliaceae) fruit extracts on the leafminer Liriomyza huidobrensis, (Diptera, Agromyzidae): Assessment in laboratory and field experiments

Control of the widely distributed pest Liriomyza huidobrensis, is complicated due to the protected habit of the leafmining larvae, and their resistance to insecticides. The effects of Melia azedarach, (Meliaceae) fruit extracts against adults and larvae of L. huidobrensis, were investigated. In the laboratory, leaves of Cucurbita, sp. infested with first and third instar larvae were treated with different extract solutions. Larval and pupal survival, as well as wing‐spread of adults, were ssessed. Female adult behaviour towards the extract was also analysed in terms of number of feeding punctures and number of offspring left on treated/untreated leaves. In the field, an infested Vicia faba, crop was sprayed four times at weekly intervals with plant extract, water, and a blank solution. The number of adult leafminers and parasitoids emerging from sampled leaves from each treatment were compared. The laboratory tests showed translaminar action of the extracts, which negatively affected leafminer pupal survival, while body size was not affected. The extracts also deterred feeding by adult females and may also have caused reduction in oviposition rates. All solutions and concentrations tested had similar effects. In the field, extract effects were consistent with those from laboratory trials, number of pupae and pupal survival being lower on treated plants. Percentage parasitism was not affected by plant extract treatment, suggesting a selective activity.     

Population growth of Rhopalosiphum padi under different thermal regimes: an agent-based model approach

1. Rhopalosiphum padi (Linnaeus, 1758) is abundant and has a broad geographic distribution. It is one of the most important cereal pests. In Brazil, the economic losses associated with this aphid result mainly from the transmission of the barley yellow dwarf viruses.
2. Decision-making for the adoption of management measures must consider the initial population size, the potential for population increase, and the time when this population will reach levels at which the resulting damage is equal to the costs of control measures. Consequently, the establishment of management programmes and decision support systems should be based on models that estimate the potential population growth of this pest species.
3. Temperature is one of the main factors that determine the growth rate of insect populations. Generally, controlled experiments are designed to examine the relationship of temperature at fixed intervals in relation to the development phases of insects. In nature, thermal regimes are not constant, and population growth is the result of a series of combined events.
4. In this work, the effects of different thermal regimes on the population growth of R. padi were compared.
5. An agent-based model was used to estimate population growth, and the parameters defined in controlled regimes were compared with fluctuating temperatures under natural conditions.
6. The temperature-driven model presented here can serve as a tool to predict population growth and decision-making for aphid management.
7. The model structure and the proposed experimental design allow the addition of modules and layers of factors that can progressively affect the populations of aphids to gradually improve the model.

     

Mass windborne migrations extend the range of the migratory locust in East China

1. Migratory insect pests pose a substantial challenge to global food security. These issues are particularly acute when pest incursions occur considerably beyond the expected range, through natural migration or human‐aided transport, because the lack of species‐specific control strategies and a potential absence of species‐specific natural enemies in the newly‐invaded area may lead to rapid establishment of a new pest.
2. One such threat is posed by the Oriental migratory locust Locusta migratoria manilensis in China, which, historically, has been restricted to eastern China from the Bohai Gulf southwards, and now threatens to expand its range into the agriculturally important region of northeast China.
3. We analyzed data from a recent outbreak of migratory locusts in Heilongjiang Province (extreme northeast China), > 700 km north of its current known range, and identified the source region, timing of arrival and probable migratory routes of this incursion.
4. We further show that warming temperatures in this region will likely allow subsequent invasions to establish permanent populations in northeast China, and thus authorities in this important crop‐producing region of East Asia should be vigilant to the threat posed by this species.

     

Local and landscape scale drivers of Euschistus servus and Lygus lineolaris in North Carolina small grain agroecosystems

1. Crop production sequences influence arthropod populations in temporally unstable row crop systems. Winter wheat (Triticum aestivum L.) represents one of the earliest abundant crops in south-eastern United States. This study aims to understand primary source habitats driving brown stink bug, Euschistus servus (Say), and tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), population abundance in wheat.
2. To better understand these relationships, adult and nymphal densities were in wheat fields weekly from flowering through harvest in 2019 and 2020. Geospatial data were used to measure landscape composition surrounding sampled fields. We investigated the influence of landscape predictors on E. servus and L. lineolaris abundance using generalized linear mixed modelling.
3. Field size, proportion of agriculture, proportion of wheat area, and proportion of soybean Glycine max L.) area from the previous year in the surrounding landscape were associated with E. servus abundance in wheat. Similarly, L. lineolaris abundance was associated with proportion of wheat area and soybean area from the previous year.
4. These results reveal the influence of soybean area planted the previous year on insect pest densities the following spring in wheat. Further, results suggest agricultural landscapes dominated by wheat are associated with decreased pest abundance across the sampled region.

     

Evaluating the link between predation and pest control services in the mite world

1. Pest regulation by natural enemies has a strong potential to reduce the use of synthetic pesticides in agroecosystems. However, the effective role of predation as an ecosystem service remains largely speculative, especially with minute organisms such as mites.
2. Predatory mites are natural enemies for ectoparasites in livestock farms. We tested for an ecosystem level control of the poultry pest Dermanyssus gallinae by other mites naturally present in manure in poultry farms and investigated differences among farming practices (conventional, free‐range, and organic).
3. We used a multiscale approach involving (a) in vitro behavioral predation experiments, (b) arthropod inventories in henhouses with airborne DNA, and (c) a statistical model of covariations in mite abundances comparing farming practices.
4. Behavioral experiments revealed that three mites are prone to feed on D. gallinae. Accordingly, we observed covariations between the pest and these three taxa only, in airborne DNA at the henhouse level, and in mites sampled from manure. In most situations, covariations in abundances were high in magnitude and their sign was positive.
5. Predation on a pest happens naturally in livestock farms due to predatory mites. However, the complex dynamics of mite trophic network prevents the emergence of a consistent assemblage‐level signal of predation. Based on these results, we suggest perspectives for mite‐based pest control and warn against any possible disruption of ignored services through the application of veterinary drugs or pesticides.

     

Seasonal decline of the tomato leafminer,Tuta absoluta,in the shifting landscape of a vegetable‐growing area

Insect pest populations exhibit seasonal dynamics in response to changes in resource availability or other environmental factors such as climatic conditions, natural enemies, and intra‐ or interspecific competition. Understanding such dynamics is critical for developing effective integrated pest management strategies. The objective of the present study was to identify factors driving the seasonal decline of the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in the shifting landscape of a vegetable‐growing area in Senegal. A set of 42 tomato fields was monitored for the number of T. absoluta adults caught in pheromone traps and for the incidence of larvae, during 5 months from June to November 2016 in the Niayes area (Senegal). The surface of solanaceous host crops, climatic conditions, and abundance of natural enemies were also monitored. A drastic decline in T. absoluta abundance was observed during the rainy season. The decrease in resource availability, especially tomato crops, in the surrounding landscape of monitored fields was the main factor affecting the population dynamics during the rainy season. However, alternative host crops such as eggplant and Ethiopian eggplant, can provide ‘reservoirs’ for residual populations of the pest. For applied purpose, it would be interesting to focus the management efforts on residual populations during the rainy season, to make more difficult the reconstitution of populations during the dry season.