Host Fruit Research Articles

Biochemical, pathological and molecular characterisation of Phomopsis vexans: A causative of leaf blight and fruit rot in brinjal

The pathogen Phomopsis vexans causes leaf blight, fruit rot, and damping off in brinjal plants, all of which are extremely detrimental. The pathogen affects host plant photosynthetic efficiency and fruit quantity and quality. An appreciation of the pathogenicity of P. vexans is essential for the effective control of infections in the field. Consequently, the goal of this study was to characterise P. vexans in terms of their biochemistry, molecular diversity, and pathogenicity. In terms of cellulase (97.7 U), catalase (12.2 U), and ascorbate peroxidase (147.3 U) activity, isolate PV1 performed best, followed by PV5 (CL-97.0 U, CAT-11.1 U and APX-144.4 U), and PV8 (CL-88.8 U, CAT-9.8 U and APX-141.9 U). In a greenhouse pathogenicity test, isolate PV1 had the highest incidence (97%) and severity (88.6%) of disease, whereas isolate PV6 showed the lowest incidence (57.2%) and severity (70%) of disease. The biochemical enzyme activity of P. vexans corresponds well with its greenhouse pathogenicity results, and its combination can be exploited to identify pathogenic P. vexans isolates. Using RAPD and ISSR primers, molecular characterisation indicated genetic diversity but could not distinguish isolates by geographical origin or pathogenicity. The pathogen P. vexans was verified by ITS1 and ITS4 molecular analysis, and the sequences were subsequently deposited in the NCBI database. In conclusion, the enzyme activity relevant to pathogenicity (CL, CAT and APX) in conjunction with the invivo pathogenicity assay might be utilised to differentiate between pathogenic (virulent) and non-pathogenic (avirulent) P. vexans isolates and develop suitable disease management strategies.

Identification of volatile compounds from fruits aroma and citrus essential oils and their effect on oviposition of Ceratitis capitata (Diptera: Tephritidae).

Ceratitis capitata (Wiedemann), also known as the Mediterranean fruit fly, is one of the most serious pests for several fresh fruit commodities causing extensive fruit losses worldwide. The response of C. capitata adults to fruit and nonfruit volatiles has been extensively studied. However, the linkage between fruit volatiles and the female ovipositional choice has not been fully elucidated. The present study focused on identifying the volatile organic compounds emitted by detached intact fresh fruits (oranges, lemons, bergamots, and apples) and citrus essential oils and evaluate their effect on Mediterranean fruit fly oviposition. There were more than 130 and 45 volatiles compounds detected in fruits odors and citrus essential oils, respectively. The volatile profile of fruits was dominated either from terpenes and terpenoids or from esters of butanoic, hexanoic, and octanoic acids while limonene was by far the most abundant compound in all citrus essential oils. Oviposition of C. capitata was strongly affected by volatiles emanated from both intact fruit and the citrus essential oils. Regarding the volatiles of the intact fruits, the odor of sweet orange elicited strong oviposition responses to females, while bergamot had the least stimulatory effect on oviposition. Bergamot oil also elicited the least oviposition stimulation compared to sweet orange and lemon essential oils. Our discussion elaborates on the role of fruit volatiles on host finding behavior and fruit susceptibility to C. capitata infestation and includes possible practical implication of the above findings.

Alternaria alternata Isolated from Infected Pears (Pyrus communis) in Italy Produces Non-Host Toxins and Hydrolytic Enzymes as Infection Mechanisms and Exhibits Competitive Exclusion against Botrytis cinerea in Co-Infected Host Fruits.

Alternaria alternata is one of the most devastating phytopathogenic fungi. This microorganism causes black spots in many fruits and vegetables worldwide, generating significant post-harvest losses. In this study, an A. alternata strain, isolated from infected pears (Pyrus communis) harvested in Italy, was characterized by focusing on its pathogenicity mechanisms and competitive exclusion in the presence of another pathogen, Botrytis cinerea. In in vitro assays, the fungus produces strong enzymatic activities such as amylase, xylanase, and cellulase, potentially involved during the infection. Moreover, it secretes four different toxins purified and identified as altertoxin I, alteichin, alternariol, and alternariol 4-methyl ether. Only alteichin generated necrotic lesions on host-variety pears, while all the compounds showed moderate to slight necrotic activity on non-host pears and other non-host fruit (lemon, Citrus limon), indicating they are non-host toxins. Interestingly, A. alternata has shown competitive exclusion to the competitor fungus Botrytis cinerea when co-inoculated in host and non-host pear fruits, inhibiting its growth by 70 and 65%, respectively, a result not observed in a preliminary characterization in a dual culture assay. Alteichin and alternariol 4-methyl ether tested against B. cinerea had the best inhibition activity, suggesting that the synergism of these toxins and enzymatic activities of A. alternata are probably involved in the competitive exclusion dynamics in host and non-host pear fruits.

Olfactory Responses of Anastrepha obliqua (Diptera: Tephritidae) to Mango Fruits as Influenced by Cultivar and Ripeness Stages.

Anastrepha obliqua Macquart (Diptera: Tephritidae) is a polyphagous species with hog plums (Spondias spp.) (Sapindales: Anacardiaceae) and mangoes (Mangifera indica L.) (Sapindales: Anacardiaceae) as primary host fruits. In this study, the olfactory preference of A. obliqua for three stages of ripeness of two mango cultivars ('Coche' and 'Ataulfo') was investigated. The female flies were more attracted to ripe 'Coche' fruits compared to those ripe 'Ataulfo'. Further, they were more attracted to the 'Coche' half-ripe and ripe fruits than to the unripe ones, but they did not discriminate among the stages of ripeness of 'Ataulfo' fruits. The male flies did not show preference for any specific mango cultivars or ripeness stage tested. Four compounds from ripe 'Coche' mangoes, and two from ripe 'Ataulfo' fruits were identified using coupled gas chromatography-electroantennographic (GC-EAD) recording and gas chromatography-mass spectrometry (GC-MS) analysis. 'Coche' mango volatiles eliciting responses from the female antennae were ethyl butyrate, ethyl hexanoate, ethyl heptanoate, and ethyl octanoate. The two 'Ataulfo' mango volatiles were identified as 3-carene and ethyl octanoate. These compounds were absent in unripe mangoes of both cultivars. Synthetic blends of these compounds were attractive to females as mango extracts in field cage tests. Our results suggest that the olfactory preference of A. obliqua for attractive hosts is based on the presence or absence of the compounds associated with fruit maturity.

Inorganic phosphate content does not affect oviposition preference in the invasive pest Drosophila suzukii

AbstractThe broad variation in host use among polyphagous insects is well documented but still poorly understood. In numerous pest insects, the proximate mechanisms responsible for variation in oviposition preference among host plants remain to be elucidated. The invasive crop pest, Drosophila suzukii, attacks a wide range of host fruits. Females prefer ovipositing on particular fruit media (blackberry, cherry, blackcurrant) that are rich in phosphorus. As phosphorus is known to be involved in female reproduction in insect species such as Drosophila, it could drive oviposition preference in D. suzukii. Phosphorus is either present as inorganic or organic phosphate in fruits. As the absolute content in macromolecules associated with phosphate in fruits (i.e. proteins and carbohydrates) do not affect oviposition in D. suzukii, we tested for the effect of inorganic phosphate on oviposition preference. We measured the egg‐laying preferences of D. suzukii in a choice environment containing 12 artificial media with increasing content in inorganic phosphate (monopotassium dihydrogen phosphate). In our assay, D. suzukii females did not prefer ovipositing in media with high inorganic phosphate content compared to media with lower inorganic phosphate content. As a confirmation, we verified the previous result of a higher female preference for media made of phosphorus‐rich fruits (blackberry, cherry, blackcurrant). The higher preference for phosphorus‐rich fruits could be driven by macromolecules containing phosphorus (e.g. phospholipids) or by the presence of one or more molecules that do not contain phosphorus, but that happen to be correlated to fruit phosphorus content. Studying the proximate mechanisms driving host use will ultimately help improve the management of D. suzukii and other crop pests.

Ovipositor characteristics differ between two parasitoids (Hymenoptera, Figitidae) of Drosophila suzukii (Diptera, Drosophilidae) in an adventive landscape

Different ovipositor characteristics among parasitoid species that share similar niches are associated with different wasp life histories and selective pressures. The length of wasp ovipositors, for example, can determine the accessibility of hosts that feed at different depths within food substrates. Two parasitoids, Ganaspis brasiliensis and Leptopilina japonica (Hymenoptera, Figitidae), which attack Drosophila suzukii (Diptera, Drosophilidae) in their native range, have been investigated for their suitability for the global biological control of the small fruit pest. Despite their sympatry in microhabitat, the parasitoids have differing host ranges, and D. suzukii parasitism rates by each parasitoid species appear to depend on the fruit species occupied by the host species. Adventive populations of both parasitoids have been detected in the Pacific Northwest of Canada and the United States where they can be found parasitizing D. suzukii larvae in crop and non-crop fruits. We dissected and measured the ovipositors of parasitoids reared from three species of fresh fruits at three sites in southwestern British Columbia, Canada, and investigated the influence of parasitoid species, fruit type, and collection site on ovipositor characteristics. We found that ovipositor length differed markedly between the two parasitoid species and between sites while ovipositor width, and stoutness, differed only between the two parasitoid species, but did not vary among sites or fruit hosts. We discuss how ovipositor morphology traits could be associated with differences in life history and host ranges in the two parasitoid species.

Maternal and host effects mediate the adaptive expansion and contraction of the microbiome during ontogeny in a holometabolous, polyphagous insect

Abstract Polyphagous, holometabolous insects adapt to rapid diet shifts imposed by their ecology and their life cycle. One shift is linked to development, as larvae and adults usually dwell and feed in different environments, using different resources. The second is caused by changes in larval hosts, often occurring at each generation. Studies show that the insect's microbiome also changes in relation to development and larval host. However, parental and larval host contributions to its structure and trans‐generational dynamics remain uncharted. We investigated the sources of variation of the microbiome of the highly polyphagous Mediterranean fruit fly by tracking microbiome structure and its potential functional impact in fly lineages over generations and fruit host shifts, using 16S rRNA gene amplicon single variant analysis. Bacterial community alpha‐diversity expanded and contracted cyclically in a life stage‐dependent manner with the mothers' microbiome community ‘resetting’ to the same structure across generations. Expansion occurred at the larval stage, while alpha‐diversity decreased in tenerals, and significantly in mothers. In contrast, richness was highest in mothers, with rare taxa expanding in larvae depending upon fruit type. Metabolic predictions using PICRUSt pointed to increased metabolism of vitamins in mothers, and of aromatic compouds in larvae and tenerals, while indicator species analysis suggested fruit host composition‐dependent potential functional adaptations. Our data indicate lineage, fruit host and their interactions as the main sources of microbiome variation and provide examples of possible metabolic developmental and ecological adaptations. Taken together, these data support the hypothesis that microbiome diversity and microbiome‐driven local adaptations act as a mechanism sustaining polyphagy. Read the free Plain Language Summary for this article on the Journal blog.

Identificación de las especies de mosca de la fruta Díptera: Tephritidae en la microcuenca de Vilcabamba, provincia de Grau, Perú

Emerging pests are increasingly threatening the health of fruit orchards throughout the Mediterranean area. Fruit flies (Diptera: Tephritidae)) are among the world's most economically important pest species, attacking a wide range of fleshy fruits and vegetables in tropical and subtropical areas. The purpose of the study was to identify the species of the Diptera fruit fly: Tephritidae and level of incidence in the Vilcabamba Micro-watershed, Grau province, Peru. The study was of a quantitative approach, descriptive level, non-experimental. A simple random probabilistic test was performed, consisting of 384 respective host fruit trees. Fruit flies captured in baited traps were collected and identified following the available taxonomic keys. To identify the species of Anastrepha spp and Ceratitis capitata, the keys of Korytkowski 2008 and SENASICA (2018) were used. A simple random probabilistic test was performed, consisting of 384 respective host fruit trees. In the results, two species of fruit fly Ceratitis capitata and Anastrepha spp were found, finding a significant correlation at the 0.01 level (bilateral) through Pearson's R and an Analysis of variance of significance level (Sig.< 0.05) between the variables under study; having a low infestation level. Ceratitis capitata and Anastrepha spp of similar appearance were distinguished. through comparative morphological analysis.

Cannibalism as Competition Strategy in Larvae of the Acorn Weevil Curculio glandium (Coleoptera: Curculionidae)

Curculio glandium is one of the pre-dispersal seed predators occurring in Central Europe. It is associated with Quercus robur, the acorns of which are shelter and food sources for developing larvae. Females of the species, to our knowledge, are lacking in marking pheromones or do not use them; therefore, in nature, multiple infestations (over 10 eggs or larvae) of the same host fruit can be found. Such density can provoke very strong competition, which was verified in this study. The survival rate and body mass of 695 second-instar larvae, competing in various test groups (one, three, five, eight and ten larvae) offered one acorn, were measured and video recordings made in order to describe their behavior and determine differences between groups. Experimental observations indicated that when the density of larvae in an acorn increased, the survival rate and body mass significantly decreased—being the lowest in test groups consisting of eight and ten individuals. In the latter groups, also the acorn embryo was completely consumed. Video footage, along with the presence of dead, nibbled larvae and living ones covered with scars resembling mouthparts, is evidence for aggression and cannibalism in the second and the third larval instars—behavior scarce in weevils and in phytophagous insects in general. Results confirm the assumption that in heavily infested oak fruits, competition between individuals is so strong that it involves cannibalism, which at the same time provides the strongest larvae with additional nutrients.

Differences in the link between female moth oviposition and larval fitness in Grapholita molesta (Lepidoptera: Tortricidae) over seasonal variation of host fruit species

Oriental fruit moth (OFM) is a cosmopolitan borer pest. Adults migrate among peach, pear or apple orchards. However, the association of female oviposition with larval fitness over seasonal variation of fruit species have not been reported. This study investigated female oviposition and larval fitness during four sampling months of peach, apple and pear related with maturity. Infested fruits were investigated in three orchards. These results showed that females laid fewer eggs on apple than peach or pear in June and July, but not May and August. Fitness index of larvae on pear was lower than peach or apple in May, June and August, except for July. In June, larvae failed completely to bore into pear. The ranking of infestation ratio was peach orchard (from June to July) > pear orchard (July onward) > apple orchard (late June onward). Based on the above results, peach (June and July) and pear (July and August) were more suitable than apple (June, July and August), whereas peach (May), apple (May) and pear (May and June) were unsuitable for OFM.

Seasonal Activity of Bactrocera zonata (Saunders) and Ceratitis capitata in a Navel Orange Orchard in Dakahlia, Egypt

El-Afify, A.H., R.M. Shreef, M.A. Hendawy and N.M. Ghanim. 2023. Seasonal Activity of Bactrocera zonata (Saunders) and Ceratitis capitata in a Navel Orange Orchard in Dakahlia, Egypt. Arab Journal of Plant Protection, 41(2): 98-104. https://doi.org/10.22268/AJPP-041.2.098104 The peach fruit fly (PFF), Bactrocera zonata (Saunders) and the Mediterranean fruit fly (MFF), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) are of the most major pests infesting citrus orchards in Egypt as well as several countries of the world. The present study was carried out to study the seasonal activity of PFF and MFF in navel orange orchards located in Dakahlia governorate, Egypt during two successive fruiting seasons of 2019/2020 and 2020/2021 by using sex attractants and fruit samples. The results obtained showed that, by using sex attractants, PFF males had two peaks each season, whereas MFF showed one to two peaks. By monitoring fruit samples, PFF exhibited one to two peaks of activity seasonally in the non-fallen and fallen fruits; whereas MFF exhibited two to three peaks on the non-fallen and fallen fruits. Both PFF and MFF were more abundant in the fallen fruits than in the non-fallen fruits. The relationships between flies trapped per day (FTD) of PFF and MFF males in Jackson traps and infestation rate of these pests showed that these traps can be used to predict infestation rates of PFF and MFF in their host fruits. Keywords: Bactrocera zonata, Ceratitis capitata, navel orange, Jackson traps, sex attractants

Response of the braconid parasitoid Diachasmimorpha longicaudata (Ashmead) to fruits infested by oriental fruit fly, Bactrocera dorsalis (Hendel)

Biological control is an increasingly employed method in the management of tephritid pests because it is ecologically benign and target specific. The parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) is considered an effective biological control agent of tephritid pests, but there are few studies on its behavioral responses to the local host types. This information is necessary for the success of the post-release establishment of the parasitoid. The parasitoid’s behavior on oriental fruit fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) infested (1 and 4d old) and uninfested fruits were assessed to understand the efficacy and preference of D. longicaudata for different host fruits. The guava was considered reference fruit to compare with banana, carambola and apple. In olfactory bioassays, the parasitoid preferred banana and guava over apple and carambola, and guava that had been infested for a longer period of time. In no-choice and dual-choice bioassays, the parasitism rate, sex ratio, and fertility were compared and in dual-choice bioassays, the parasitoid exhibited significant differences of the above parameters in guava-banana and guava-carambola but not in the guava-apple trial. In the no-choice bioassays, nothing differs substantially between guava and other fruits except the parasitism rate of guava and banana which was significantly greater in guava. This study will help to understand the post-release behavior of the parasitoid to implement the integrated pest management programs of the oriental fruit fly.

Spotted-wing drosophila, Drosophila suzukii (Diptera: Drosophilidae), exhibits large-scale spatial genetic structure across Canada but not fruit host–associated genetic structure

Abstract Spotted-wing drosophila, Drosophila suzukii, is a global pest of soft fruits that is capable of reproducing on a wide range of cultivated and wild plant species. In Canada, D. suzukii was first reported in British Columbia in 2009 and is now widespread across the country. Understanding the genetic structure of D. suzukii populations could be important for pest management if there are phenotypic differences between genetically distinct populations. For example, insect pest populations could respond differently to directional selection imposed by insecticides, differ in their host plant preferences, and vary in their susceptibility to biological control agents. Here, we used double-digest restriction site–associated DNA sequencing to examine large- and fine-scale patterns of the genetic structure of D. suzukii reared from fruit hosts in Canada. We found that this species has a large-scale spatial genetic structure; the flies collected formed two distinct genetic clusters, one of which was distinct to western Canada and the other to eastern Canada. At the local scale, D. suzukii populations showed no evidence of host-associated structuring in British Columbia, suggesting that pest management tactics may be best applied at the landscape level. Our results highlight the need to investigate phenotypic differences between western and eastern D. suzukii populations in Canada.

Drosophila suzukii energetic pathways are differently modulated by nutritional geometry in males and females

As a polyphagous pest, Drosophila suzukii has a variety of host fruits available for feeding and oviposition, but how the nutritional geometry of different hosts influences its metabolism is still poorly understood. This work aimed to evaluate how D. suzukii metabolic and transcriptional pathways are influenced by feeding on different host fruits, and how sex influences these responses. Adult flies were allowed to feed on five different fruit-based media. Lipids, glucose, glycogen, and energy pathways-associated gene expression, were quantified. Females showed an energetic metabolism easily adaptable to the food’s nutritional characteristics; in contrast, males’ energetic metabolism was particularly influenced by food, predominantly those fed on raspberry media who showed changes in glucose levels and in the expression of genes associated with metabolic pathways, suggesting activation of gluconeogenesis and trehaloneogenesis as a result of nutritional deficiency. Here we present novel insight into how D. suzukii’s energetic pathways are modulated depending on fruits’ nutritional geometry and sex. While the females showed high adaptability in their energetic metabolism to the diet, males were more feeding-sensitive. These findings might be used not only to control this pest population but to better advise producers to invest in less suitable fruits based on the hosts’ nutritional geometry.

Range expansion and population dynamics of Bactrocera carambolae in Roraima, Brazil

The carambola fruit fly Bactrocera carambolae Drew & Hancock (Diptera: Tephritidae) is the main pest that threatens Brazilian fruit production, and can cause serious economic losses. Native to southeast Asia, B. carambolae was introduced in Brazil in 1996 and is currently found in the states of Amapá, Roraima and northern Pará, where an eradication program is underway. In this study, we studied the range expansion of B. carambolae and the association of climate with seasonal dynamics in Roraima, Brazil, from January 2013 to December 2020. Monitoring of B. carambolae adults was carried out through Jackson and McPhail trapping. The highest densities of B. carambolae occurred in the northeast region of Roraima. Low densities occurred in central Roraima, and a single outbreak was observed in south Roraima in 2014, but it was eradicated. Pest abundance was positively correlated with air relative humidity. These results can assist with control efforts and eradication programs of B. carambolae by indicating the periods with higher pest pressure and potential regions for pest establishment. This study will help to improve strategies for surveillance and host fruit transport.

Rapid and transient evolution of local adaptation to seasonal host fruits in an invasive pest fly.

Both local adaptation and adaptive phenotypic plasticity can influence the match between phenotypic traits and local environmental conditions. Theory predicts that environments stable for multiple generations promote local adaptation, whereas highly heterogeneous environments favor adaptive phenotypic plasticity. However, when environments have periods of stability mixed with heterogeneity, the relative importance of local adaptation and adaptive phenotypic plasticity is unclear. Here, we used Drosophila suzukii as a model system to evaluate the relative influence of genetic and plastic effects on the match of populations to environments with periods of stability from three to four generations. This invasive pest insect can develop within different fruits, and persists throughout the year in a given location on a succession of distinct host fruits, each one being available for only a few generations. Using reciprocal common environment experiments of natural D.suzukii populations collected from cherry, strawberry, and blackberry, we found that both oviposition preference and offspring performance were higher on medium made with the fruit from which the population originated than on media made with alternative fruits. This pattern, which remained after two generations in the laboratory, was analyzed using a statistical method we developed to quantify the contributions of local adaptation and adaptive plasticity in determining fitness. Altogether, we found that genetic effects (local adaptation) dominate over plastic effects (adaptive phenotypic plasticity). Our study demonstrates that spatially and temporally variable selection does not prevent the rapid evolution of local adaptation in natural populations. The speed and strength of adaptation may be facilitated by several mechanisms including a large effective population size and strong selective pressures imposed by host plants.

Is Fopius arisanus (Hymenoptera: Braconidae) a suitable biological control agent of Bactrocera dorsalis (Diptera: Tephritidae) in multi-crop orchards?

In the present study, we investigated the bottom-up effects of four economically important host fruit species (guava, mandarin orange, plum, pear) on Bactrocera dorsalis parasitoid Fopius arisanus in terms of emergence, parasitism, sex ratio, developmental duration, longevity and body size. Our results showed that F. arisanus reared on guava infested with B. dorsalis had highest emergence, parasitism, sex ratio and longevity, while these parameters were lower on B. dorsalis-infested mandarin orange. Moreover, body size of F. arisanus (wing, hind tibia and body lengths for both sexes and ovipositor length for female) varied significantly among the B. dorsalis-infested fruits, with mandarin orange providing the biggest emergent body size for both sexes and guava providing the smallest. The shortest preimaginal developmental time for both sexes was in infested plums and the longest in infested mandarin orange. Therefore, we inferred that B. dorsalis-infested guava is the most suitable host–host plant combination for F. arisanus fitness among the tested fruit-host combinations. Our findings corroborates that the ability of some tested fruit species to serve for the permanent establishment of F. arisanus in the field, which will aid in boosting the efficiency of F. arisanus as a biological control agent, especially in multi-crop orchards.

Sexual competitiveness of sterile Ceratitis capitata males exposed to essential oils from non‐host plant species native to Argentina

AbstractThe sterile insect technique (SIT) is used to control fruit fly pests, such as the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Enhancing sexual competitiveness of mass‐reared sterile males can contribute to making this technique more effective. It has been shown that exposure to volatiles from essential oils (EOs), such as ginger root oil (GRO) and those from host fruits, increases male mating success. We evaluated the effect of EOs from non‐host species native to Argentina, Schinus polygama (Cav.) Cabrera (Anacardiaceae) and Baccharis spartioides (Hook. &amp; Arn.) Remy (Asteraceae), on the sexual competitiveness of sterile C. capitata males. In field cage experiments, sterile males exposed to S. polygama EO increased their mating success. In addition, sterile males exposed to this EO achieved more matings on trees than non‐exposed males, thus suggesting the former are more prone to locate and defend the pheromone‐calling territory. Deprivation of water and/or food significantly reduced males' life span, but exposure to S. polygama EO and GRO did not affect their survival. Schinus polygama EO is composed of mono‐ and sesquiterpenes with behavioral and electroantennographic responses in medflies, indicating that semiochemicals that boost medfly sexual competitiveness combine in this EO.

Differential responses of Bactrocera dorsalis and its parasitoids to headspaces of different varieties of tree-attached mango fruits and the associated chemical profiles

Bactrocera dorsalis (Hendel) is a major pest of fruits and vegetables worldwide with documented losses of up to 100%. Various management techniques including the use of parasitoids, such as Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) within the context of the Integrated Pest Management (IPM) approach have been deployed for its control. The effectiveness of parasitoids is well understood, but knowledge of the semiochemicals that mediate their behavior, as well as that of the host fruit fly to tree-attached mangoes, is lacking. Here, we first compared the attractiveness of the above-mentioned fruit fly and its parasitoids to volatiles of different treatments (non-infested physiologically mature unripe and ripe mangoes, mangoes newly exposed to ovipositing B. dorsalis, and mangoes on day 7 and day 9 post-oviposition) of tree-attached Kent, Apple, and Haden mango varieties relative to control (clean air). The fruit fly was significantly more attracted to the mango volatiles (up to 93% of responsive insects) compared to the control (clean air). Fopius arisanus was significantly more attracted to mangoes with ovipositing fruit flies (68–76%) while D. longicaudata was significantly more attracted to day 9 post-oviposited mangoes (64–72%) compared to the control. Secondly, we elucidated the headspace volatile profiles of the non-infested and infested tree-attached mangoes using gas chromatography linked to mass spectrometry (GC-MS). The volatiles revealed various types of organic compounds with qualitative and quantitative differences. The majority of the compounds were esters making 33.8% of the total number, followed by sesquiterpenes-16.4%, and monoterpenes-15.4% among others. Most compounds had higher release rates in headspace volatiles of fruit fly-infested mangoes. Lastly, we harvested the infested mangoes and incubated them for puparia recovery. The number of puparia recovered varied according to the mango variety with Apple mango registering 81.7% of the total, while none was recovered from Kent. These results represent the first report of the changes in the headspace components of non-infested and infested tree-attached mangoes and the associated differential responses of the mentioned insects. A follow-up study can reveal whether there is a convergence in olfactomes which is significant when developing baits that selectively attract the fruit fly and not its natural enemies and fill the knowledge gap from an evolutionary ecological perspective.

Plant-host shift, spatial persistence, and the viability of an invasive insect population

Assessing the effects of a plant-host shift is important for monitoring insect populations over long time periods and for interventions in a conservation or pest management framework. In a heterogeneous environment, individuals may disperse between sources and sinks in order to persist. Here we propose a single-species two-patch model that aims to capture the generational movement of an insect that exhibits density-dependent dispersal, to see how shifting between hosts could alter its viability and asymptotic dynamics. We then analyse the stability and persistence properties of the model and further validate it using parameter estimates derived from laboratory experiments. In order to evaluate the potential of this model, we applied it to Drosophila suzukii (Diptera: Drosophilidae), which has become a harmful pest in several countries around the world. Although many studies have investigated the preference and attractiveness of potential hosts on this invasive drosophilid, no studies thus far have investigated whether a shift of fruit host could affect such a species’ ecological viability or spatiotemporal persistence. The model results show that a shift in host choice can significantly affect the growth potential and fecundity of a species such as D. suzukii, which ultimately could aid such invasive populations in their ability to persist within a changing environment.