Insect Pests Of Crops Research Articles

Automated aerosol puffers effectively deliver 1-OCTEN-3-OL, an oviposition antagonist useful against spotted-wing drosophila.

Automated aerosol puffers releasing behaviorally active volatile organic compounds can deter insect pests in crops. During 2016, we tested the efficacy of aerosol puffer arrays emitting 1-octen-3-ol at reducing Drosophila suzukii oviposition in fall-bearing raspberries in Western New York State. During 2017, we compared the performance of aerosol puffers with a passive diffusion release method (vial dispensers), as well as puffer timing and placement within the field. During 2016, we found that octenol application in the field via aerosol puffer systems resulted in a 20% decrease in D. suzukii oviposition compared to control plots. During 2017, we found that aerosol puffers releasing octenol were 42-55% more effective than vial dispensers at deterring oviposition. We also found that a discontinuous application of octenol during dawn and dusk was sufficient to deter D. suzukii oviposition equivalent to continuous applications throughout the day. Although we observed no differences in infestation depending on puffer placement, low fly populations at the time of the trial may have affected the data. Our data indicate that automated aerosol puffer systems may reduce D. suzukii infestation to a greater extent than vial dispensers. If adopted, a discontinuous puffer release schedule may protect both economic and ecological interests by reducing the amount of material required to achieve efficacy. Further research on puffer placement is needed to determine whether perimeter applications are effective in larger scale field research and in combination with attractants as part of a push-pull management system.

Determination of fitness traits of Orius strigicollis Poppius (Hemiptera: Anthocoridae) on Pectinophora gossypiella (Lepidoptera: Gelechiidae) using two-sex life table analysis.

BackgroundPink bollworm (Pectinophora gossypiella) is a destructive insect pest of cotton crops in China and globally, which is actively predated on by Orius strigicollis. Studies on the fitness or survival of O. strigicollis fed on P. gossypiella at different temperatures have not been reported. The fitness of O. strigicollis may be well explained using two-sex life table parameters. Thus, the present study provides important insights for the effective biocontrol of P. gossypiella.MethodologyConsidering the importance of fitness parameters and biocontrol, the present study explores the feeding potential and age-stage, two-sex life table traits of O. strigicollis on P. gossypiella eggs at different temperatures (24, 28 and 32 °C) in the laboratory.ResultsThe intrinsic rate of increase (r) was higher at 28 °C (0.14 d−1) than at 24 °C (0.0052 d−1) and 32 °C (0.12 d−1). Similarly, the net reproductive rate (R0) was higher at 28 °C (17.63 offspring) than at 24 °C (1.13 offspring) and 32 °C (10.23 offspring). This concluded that the maximum feeding potential and growth capacity of O. strigicollis could be attained at 28 °C when fed on P. gossypiella eggs. O. strigicollis adults preferred to feed on P. gossypiella eggs compared with first instar larvae. Based on these results, the present study suggests that O. strigicollis represents a promising biological control agent against P. gossypiella eggs in cotton fields.

Effect of gamma irradiation and subsequent cold storage on the development and predatory potential of seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera; Coccinellidae) larvae

Seven spot ladybird beetle, (Coccinella septempunctata) is a widely distributed natural enemy of soft-bodied insect pests especially aphids worldwide. Both the adult and larvae of this coccinellid beetle are voracious feeders and serve as a commercially available biological control agent around the globe. Different techniques are adopted to enhance the mass rearing and storage of this natural enemy by taking advantage of its natural ability to withstand under extremely low temperatures and entering diapause under unfavorable low temperature conditions. The key objective of this study was to develop a cost effective technique for enhancing the storage life and predatory potential of the larvae of C. septempunctata through cold storage in conjunction with the use of nuclear techniques, gamma radiations. Results showed that the host eating potential of larvae was enhanced as the cold storage duration was increased. Gamma irradiation further enhanced the feeding potential of larvae that were kept under cold storage. Different irradiation doses also affected the development time of C. septempuntata larvae significantly. Without cold storage, the lower radiation doses (10 and 25 GY) prolonged the developmental time as compared to un-irradiated larvae. Furthermore, the higher dose of radiation (50GY) increased the developmental time after removal from cold storage. This study first time paves the way to use radiation in conjunction with cold storage as an effective technique in implementation of different biological control approaches as a part of any IPM programs

Comparative Microbiomics of Tephritid Frugivorous Pests (Diptera: Tephritidae) From the Field: A Tale of High Variability Across and Within Species

The family Tephritidae includes some of the most notorious insect pests of agricultural and horticultural crops in tropical and sub-tropical regions. Despite the interest in the study of their gut microbiome, our present knowledge is largely based on the analysis of laboratory strains. In this study, we present a first comparative analysis of the gut microbiome profiles of field populations of ten African and Mediterranean tephritid pests. For each species, third instar larvae were sampled from different locations and host fruits and compared using 16S rRNA amplicon sequencing and a multi-factorial sampling design. We observed considerable variation in gut microbiome diversity and composition both between and within fruit fly species. A “core” microbiome, shared across all targeted species, could only be identified at most at family level (Enterobacteriaceae). At genus level only a few bacterial genera (Klebsiella, Enterobacter, and Bacillus) were present in most, but not all, samples, with high variability in their relative abundance. Higher relative abundances were found for seven bacterial genera in five of the fruit fly species considered. These were Erwinia in Bactrocera oleae, Lactococcus in B. zonata, Providencia in Ceratitis flexuosa, Klebsiella, and Rahnella in C. podocarpi and Acetobacter and Serratia in C. rosa. With the possible exception of C. capitata and B. dorsalis (the two most polyphagous species considered) we could not detect obvious relationships between fruit fly dietary breadth and microbiome diversity or abundance patterns. Similarly, our results did not suggest straightforward differences between the microbiome profiles of species belonging to Ceratitis and the closely related Bactrocera/Zeugodacus. These results provide a first comparative analysis of the gut microbiomes of field populations of multiple economically relevant tephritids and provide base line information for future studies that will further investigate the possible functional role of the observed associations.

Characteristics of biochemical resistance mechanism of novel insecticides in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

Phenacoccus solenopsis Tinsley is a major sap-sucking insect pest of many ornamental and agricultural crops in Pakistan. Insecticides are recommended to manage P. solenopsis but due to inappropriate use of insecticides, the resistance become the major concern. The study was conducted to investigate resistance against insecticides with different action modes (carbosulfan, clothianidin and chlorfenapyr) by selecting P. solenopsis populations successively for twelve generations with mentioned insecticides. Along with, possible biochemical mechanisms (acetylcholinesterase (AChE), acid and alkaline phosphatases (ACP and ALP), esterase (EST) and glutathione S-transferases (GST)) were assessed. The results described very high resistance (235-fold) to carbosulfan selected pop. (Carbo-SEL G12) and clothianidin selected pop. (Cloth-SEL G12) (112-fold) and high resistance to chlorfenapyr selected pop. (Chlor-SEL G12) (86-fold), relative to the unselected population. The activities of AChE, ACP, ALP, EST and GST enzymes gradually increased upon selection from G1 to G10. The enzymes contribute in resistance of tested insecticides were following: EST (15.61 μmol/min/mg of protein) in Carbo-SEL G12. Whereas, AChE activity (21.5 μmol/min/mg of protein) in Cloth-SEL G12 and the highest ALP enzymes activity 16.57 μmol/min/mg of protein in Chlor-SEL G12, as compared to the unselected population. Current research suggests that the detoxifying enzymes may contribute to resistance evolvement in P. solenopsis and this information may be used for the efficient management of insecticide resistance.

Indigenous biobed to limit point source pollution of imidacloprid in tropical countries

Point pollution of pesticides originating from the washing of spraying machines could be controlled by biobed system and it is in use in temperate countries. The biobed system is yet to be established in tropical countries. An indigenous biobed system was prepared using local resources like rice straw, farm yard manures (FYM) and paddy field soil to suit the tropical climate. Lowermost 3 cm layer of the biobed system was filled with rice husk biochar to prevent leaching of pesticides from the system. This model system was tested with high doses of imidacloprid (178 mg/column), a commonly used pesticide against number of insect-pests in different crops, for its degradation. The bio-mix trapped a major part of the imidacloprid on the top most layer of the biobed column and only a very small part of imidacloprid recovered from the leachate. The biobed system could degrade 70.13% of applied imidacloprid within 15 days of the experiment and only 5.27% of the total pesticide recovered 90 days after incubation. Addition of biochar layer adsorbed imidacloprid from the outgoing leachate from the biobed column. Biomixture boosted microbial activity more particularly fungal population, which might be responsible for imidacloprid degradation. Microbial biomass carbon, and soil enzymes indicated faster dissipation of imidacloprid from the top layer of the biobed. This simple but efficient biobed system using local resources can fulfill the need of the small and marginal farmers of Asian countries for pesticide decontamination.

Isolation, identification and biocontrol potential of entomopathogenic nematodes occurring in Purvanchal and Bundelkhand regions of Uttar Pradesh, India

Entomopathogenic nematodes (EPNs) are being used for the management of insect pests occurring in both agricultural and horticultural crops. But native EPNs are reasonably more efficacious in controlling insect pests than introduced EPNs species because they are adapted to local environmental conditions and insect pests. Therefore, in the present study, a survey was conducted to isolate EPNs at 4 districts of Purvanchal Region and 1 district of Bundelkhand Region of Uttar Pradesh, India, between 2016 and 2017 years. Out of 130 soil samples, EPNs were recovered from 3 soil samples (2.3%). Morphological characters examination and ITS-rDNA region revealed that the 3 EPNs such as Steinernema sp. (IIVR JNC01 strain) Steinernema sp. (IIVR JNC02 strain), and Steinernema sp. (IIVR EPN03 strain) are belonging to Steinernema siamkayai. Further pathogenicity of all these strains was tested on Galleria mellonella Linnaeus and the most effective strain was used to determine the biocontrol potential against lepidopteran and coleopteran pests of major vegetable crops in comparison to commercially available Heterorhabditis indica (NBAIIH38 strain). Results revealed that S. siamkayai (IIVR JNC01 strain) caused 100, 100, and 85%, mortality of 3rd instar larvae of Spodoptera litura Fabricius, Spilosoma obliqua Walker, and Spoladea recurvalis Fabricius, respectively. Similarly, S. siamkayai (IIVR JNC01 strain) caused 92.5% mortality of 2nd instar grubs of Myllocerus subfaciatus Gurein under laboratory conditions. The present study revealed that EPNs commonly present at Purvanchal and Bundelkhand regions of Uttar Pradesh and S. siamkayai (IIVR JNC01 strain) isolated from the Bundelkhand Region showed a good biocontrol potential against major insect pests of vegetable crops.

Biorational strategies for the management of insect pests of spice crops

Pest control strategies based on relatively non-toxic procedures that preserve the health of the ecosystem and minimizes negative effects on beneficial organisms, and utilize microbial pathogens and their products, plant natural products, semiochemicals, biotechnological strategies and reduced-risk pesticides can be termed as ‘biorational strategies’. This review consolidates the information available on the use of biorational strategies for the management of insect pests of spice crops such as Piper nigrum (black pepper), Elettaria cardamomum (cardamom), Zingiber officinale (ginger), Curcuma longa (turmeric), Coriandrum sativum (coriander), Cuminum cyminum (cumin) and Foeniculum vulgare (fennel). The review also identifies the current gaps in knowledge and the opportunities and challenges in using biorational strategies for the production of clean spices, reflecting the global concern over pesticide misuse.

Fitness cost, realized heritability and stability of resistance to spiromesifen in house fly, Musca domestica L. (Diptera: Muscidae)

The house fly, Musca domestica L. (Diptera: Muscidae), is an insect pest of public health and veterinary importance. Spiromesifen is a new chemistry insecticide widely used for the management of sucking insect pests of vegetables and crops. In the present study, assessment of resistance risk and fitness costs associated with spiromesifen resistance in M. domestica was studied. Moreover, stability of resistance to spiromesifen and other tested insecticides (fipronil, spinosad, and bifenthrin) was evaluated in the spiromesifen-selected-strain (SPIRO-SEL-POP). After 7-generations of selection with spiromesifen, SPIRO-SEL-POP developed 108.76-fold resistance compared with the unselected strain (UNSEL-POP). The estimated value of realized heritability was 0.59 for spiromesifen resistance. Due to withdrawal of spiromesifen selection for five generations (F6-F10) on SPIRO-SEL-POP, a decline in LC50 values against spiromesifen, spinosad and bifenthrin was 0.16, 0.14 and 0.13-folds, respectively. In biological trait experiments, larval weight of Cross1 (SPIRO-SEL-POP♀ × UNSEL-POP♂) and SPIRO-SEL-POP was significantly lower than that of Cross2 (SPIRO-SEL-POP♂ × UNSEL-POP♀) and UNSEL-POP. Pupal weight of SPIRO-SEL-POP was higher when compared with Cross1 while it was similar to that of Cross2 and UNSEL-POP. Adult emergence rate of UNSEL-POP was higher than Cross1, but similar to the Cross2 and SPIRO-SEL-POP. The SPIRO-SEL-POP and Cross1 showed the lowest relative fitness when compared with USEL-POP and Cross2. Intrinsic rate of natural increase of SPIRO-SEL-POP was much lower than that of UNSEL-POP and Cross2 followed by Cross1. The SPIRO-SEL-POP exhibited lower biotic potential when compared with UNSEL-POP and Cross2 but similar to Cross1. Fecundity and hatching rates were lower in SPIRO-SEL-POP compared to UNSEL-POP. It could be concluded that spiromesifen resistance in M. domestica comes with a cost and is instable. Therefore, spiromesifen rotation with other insecticides and withdraw of its usage for some period could help to sustain its efficacy by delaying the development of resistance.

Adoption by adaptation: moving from Conservation Agriculture to conservation practices

ABSTRACT Conservation Agriculture (CA) is a Sustainable Agricultural Intensification strategy based on minimum soil disturbance, permanent soil coverage by living or dead biomass, and diversification of crop rotations. We reviewed the literature on benefits, trade-offs, adoption and adaptation of CA in sub-Saharan Africa (SSA). While CA can improve soils and sustain crop yields, benefits are inconsistent and there are trade-offs with crop residue use, weeds and insect pests, labour demands and short-term yield penalties. Adoption rates by smallholders in sub-Saharan Africa are generally low. We hypothesize that underlying adoption constraints are 1) the magnitude of transformation of management practices required from farmers moving to CA, 2) the multiple inherent trade-offs associated with CA practices and 3) the incompatibility of CA practices to local conditions. We suggest CA adoption in SSA could be improved by focusing the promotion of CA to environments where it best fits, or by facilitating smallholders’ adaptation of the practices of CA to respond to their conditions and constraints. We, therefore, propose to move from Conservation Agriculture to Conservation Practices by: (A) identifying and overcoming locally important CA trade-offs through adaptations and complementary practices, and (B) finding farm-specific optimal combinations of practices in terms of feasibility and benefits.

Attack and aggregation of a major squash pest: Parsing the role of plant chemistry and beetle pheromones across spatial scales

Abstract Successful management of insect crop pests requires an understanding of the cues and spatial scales at which they function to affect rates of attack of preferred and non‐preferred host plants. A long‐standing conceptual framework in insect–plant ecology posits that there is hierarchical structure spanning host location, acceptance and attack that could be exploited for integrated pest management. We investigated how plant‐ and insect‐derived chemical cues affect successive decisions of host choice in aggregating insects, and tested predictions in the Cucurbita pepo–Acalymma vittatum system. Acalymma vittatum is an aggregating specialist beetle pest that strongly prefers zucchini (C. p. pepo) to summer squash (C. p. ovifera), two independent domesticates of C. pepo. We hypothesized that subspecies‐specific plant traits, especially volatile cues, interact with the male‐produced aggregation pheromone to amplify beetle preference for C. p. pepo. Differential beetle attack of C. pepo subspecies in the field is not determined by plant traits that affect host finding or differential aggregation due to pheromones: across two years, beetles had strong density‐dependent attraction to both subspecies when male beetles were feeding, and no interactions between plant volatiles and the male‐produced pheromone were detected. In the absence of male pheromone emission, beetles were equally unattracted to plants with or without beetle feeding. In contrast, plant traits that mediate insect acceptance appear to underlie differences in preference. At a local scale, beetles did not accept and emigrated from C. p. ovifera compared to C. p. pepo. Distinct volatile emissions were observed between subspecies, but further work is needed to identify if these volatiles promote emigration. Synthesis and applications. By dissecting pest preference during successive host choice decisions, we isolated a trait with implications for pest management. Beetles on cucurbits can be managed by employing cultivars with differential susceptibility (e.g. trap cropping), and the mechanistic knowledge presented here informs best practices and limitations for on‐farm applications. More broadly, pest management in diversified cropping systems can be enhanced through understanding how plant preference gradients affect herbivore movement and behaviour, and plant breeders can target traits to reduce herbivory in such systems.

Susceptibility of fall armyworm, Spodoptera frugiperda (J.E. Smith), to eight insecticides in China, with special reference to lambda-cyhalothrin

Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is the main destructive insect pest of grain crops that occurs in all maize growing regions of the Americas. It has rapidly invaded the Southern China since January 2019. However, the current status of insecticide resistance in S. frugiperda has not been reported in China. In this study, we determined the susceptibility of eight populations of FAW to eight insecticides by an artificial diet incorporation method. The results showed that among eight insecticides, emamectin benzoate, spinetoram, chlorantraniliprole, chlorfenapyr, and lufenuron showed higher toxicity to this pest, while lambda-cyhalothrin and azadirachtin exhibited lower toxicity. Susceptibility of S. frugiperda to indoxacarb was significantly different (10.0-fold for LC50) across the various geographic populations. To investigate the biochemical mechanism of FAW to lambda-cyhalothrin, we performed the synergism tests and the results showed that piperonyl butoxide (PBO) and triphenyl phosphate (TPP) produced a high synergism of lambda-cyhalothrin effects in the two field populations. Sequencing of the gene encoding the acetylcholinesterase (AChE) gene in the two field populations identified two amino acid mutations, all of which have been shown previously to confer resistance to organophosphates (OPs) in several arthropod species. The results of this study provided valuable information for choosing alternative insecticides and for insecticide resistance management of S. frugiperda.

Optimization of Nitrogen Fertilizer Application Enhances Biocontrol Function and Net Income.

The intensive use of nitrogen fertilizer has been a common approach for pursuing higher crop yields. However, the ecological effects of such use on the tritrophic interactions (crop-insect pest-natural enemy) and on the ecological and economic benefits of such use are poorly understood. Here, we investigated the effects of low, medium, and high levels of nitrogen fertilizer inputs (70, 140, and 280 kg/ha/yr) on cereal aphid (Sitobion avenae Fabricius [Hemiptera: Aphididae], Schizaphis graminum Rondani [Hemiptera: Aphididae], and Rhopalosiphum padi L. [Hemiptera: Aphididae]) abundance, primary parasitism rates, crop yield, and net income in winter wheat (Triticum aestivum [Poales: Poaceae] cv. Zhou 22) for 2 yr. A higher input of nitrogen fertilizer significantly enhanced the abundance of cereal aphids, while their primary parasitism rates (26.9 ± 3.5% in 2018 and 24.9 ± 4.5% in 2019) were highest at the medium nitrogen level. The performance of participants in the wheat-aphids-parasitoids system was likewise mediated by the nitrogen fertilizers. Meanwhile, wheat yield significantly increased with moderate increases in the nitrogen level, although overuse of nitrogen fertilizer did not significantly further enhance wheat yield. Finally, we found either low or overuse of nitrogen fertilizers resulted in lower net income than did medium nitrogen fertilization. These results demonstrate the need to reevaluate and adjust fertilizer use to optimize the eco-economic and sustainable management of agroecosystems.

Fumigant toxicity of three Satureja species on tomato leafminers, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is one of the major insect pests of solanaceous crops especially tomatoes. As plants contain secondary metabolites with protective properties against unwanted agents, they can be used as insecticides after extraction from plants as essential oils (EOs). In this study, essential oils of three savory species, including Satureja khuzestanica, S. bachtiarica, and S. rechingeri were extracted. Analyzing the chemical compositions via gas chromatography–mass spectrometry (GC/MS) revealed that geraniol was the main component of all essential oils. The volatile activity of these three savory species on the fourth instar larvae of T. absoluta during 24 h, indicated that LC50 values of S. khuzestanica, S. bachtiarica, and S. rechingeri oils were 17.51, 25.03, and 34.33 μgL−1(air), respectively. Enzyme assays in vivo using alpha-naphthyl acetate (α-NA) as a substrate, showed that in the fourth instar larvae treated with 10 percent lethal concentration (LC10), general esterases of these larvae increased significantly in all treatments (p < .05). Polyacrylamide gel electrophoresis with a solution mixture of both substrates (α-and ß-NA) clarified three bands of esterases. However, this method failed to show any sublethal effects of the oils (LC10 value) on the larvae esterase bands. Considering the potential toxicity of these three species of Satureja essential oils to the tomato leafminers due to existence of several secondary metabolites, we can expect that new bio-pesticides can be developed from these promising plants in near future.

Crop Varietal Mixtures as a Strategy to Support Insect Pest Control, Yield, Economic, and Nutritional Services

Most on-farm diversification strategies to enhance ecosystem services, such as insect pest control and yield, have focused on expanding crop species diversity. While polycultures often provide valuable services, logistical constraints with planting and harvesting can hamper implementation on large scales. An alternative diversification strategy is to increase within-field intraspecific crop diversity through the use of crop varietal mixtures. Here, we evaluate an interdisciplinary body of research to determine the potential for crop varietal mixtures to support food security by providing ecological, economic, and nutritional services. Previous literature has synthesized the link between varietal mixtures and yield and insect pest suppression services. We expand on prior analyses by considering hypotheses generated from species-level research and assessing whether they also provide a useful framework for predicting how varietal mixtures affect crop productivity and insect pest suppression. In addition, we evaluate the potential for varietal mixtures to increase farm resilience and growers’ profits. While there is a growing effort to quantify the economic value of ecosystem services provided by agrobiodiversity in terms of enhanced yield or revenue, much less attention has been given to quantifying the production costs associated with diversification schemes. Consequently, we know little about the effect of diversification practices on farm profitability, the metric of ultimate importance to farmers. We address this issue by evaluating the ability of varietal mixtures to reduce production costs associated with other types of agrobiodiversity and outline areas for future research to better understand the profit implications of varietal mixtures. Further, we review evidence that varieties of some crop species differ in phytochemical content—a functional trait important for insect pest suppression and human dietary diversity—suggesting that varietal mixtures could be designed to simultaneously support insect pest control and human nutrition services. Given that little research has explicitly addressed the capacity for varietal mixtures to support human nutrition, we outline predictions for where we would expect to see the greatest nutritional impact of mixtures, providing a foundation for future human nutrition research. Taken together, our review suggests that varietal mixtures are a promising and logistically feasible strategy that could simultaneously support multiple services.

Virome Analysis of Aphid Populations That Infest the Barley Field: The Discovery of Two Novel Groups of Nege/Kita-Like Viruses and Other Novel RNA Viruses.

Aphids (order Hemiptera) are important insect pests of crops and are also vectors of many plant viruses. However, little is known about aphid-infecting viruses, particularly their diversity and relationship to plant viruses. To investigate the aphid viromes, we performed deep sequencing analyses of the aphid transcriptomes from infested barley plants in a field in Japan. We discovered virus-like sequences related to nege/kita-, flavi-, tombus-, phenui-, mononega-, narna-, chryso-, partiti-, and luteoviruses. Using RT-PCR and sequence analyses, we determined almost complete sequences of seven nege/kitavirus-like virus genomes; one of which was a variant of the Wuhan house centipede virus (WHCV-1). The other six seem to belong to four novel viruses distantly related to Wuhan insect virus 9 (WhIV-9) or Hubei nege-like virus 4 (HVLV-4). We designated the four viruses as barley aphid RNA virus 1 to 4 (BARV-1 to -4). Moreover, some nege/kitavirus-like sequences were found by searches on the transcriptome shotgun assembly (TSA) libraries of arthropods and plants. Phylogenetic analyses showed that BARV-1 forms a clade with WHCV-1 and HVLV-4, whereas BARV-2 to -4 clustered with WhIV-9 and an aphid virus, Aphis glycines virus 3. Both virus groups (tentatively designated as Centivirus and Aphiglyvirus, respectively), together with arthropod virus-like TSAs, fill the phylogenetic gaps between the negeviruses and kitaviruses lineages. We also characterized the flavi/jingmen-like and tombus-like virus sequences as well as other RNA viruses, including six putative novel viruses, designated as barley aphid RNA viruses 5 to 10. Interestingly, we also discovered that some aphid-associated viruses, including nege/kita-like viruses, were present in different aphid species, raising a speculation that these viruses might be distributed across different aphid species with plants being the reservoirs. This study provides novel information on the diversity and spread of nege/kitavirus-related viruses and other RNA viruses that are associated with aphids.

Fruit fly management in Nepal: A case from plant clinic

Fruit fly is one of the important insect pests of horticultural crops, both fruits and vegetables. After aphids, fruit fly was reported as a major insect problem in the plant clinic sessions from September 2013 to July 2016 in Nepal. The groups of horticultural crops most affected by fruit flies were cucurbitaceous vegetables, i.e. 79% of all fruit fly queries (bitter gourd, bottle gourd, chayote, cucumber, pumpkin, snake gourd, sponge gourd and squash) followed by fruits 14% (guava, sweet orange, mandarin, mango, peach, and pomegranate) and solanaceous vegetables 6% (brinjal, chillies and tomato). The fruit fly management measures, such as use of para-pheromone lure/traps, sanitation and cultural measures were mostly referred in plant clinics by plant doctors of Nepal. The availability of para-pheromone lures/traps as well as technical know-how of application focusing integrated management measures should be adopted to manage fruit fly in horticultural crops with the least disruption to the environment and human health.

Natural occurrence of entomopathogenic fungus, Cladosporium cladosporioides on blow fly, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) on ber in Punjab, India

Surveys and surveillances were carried out in the ber growing regions of Punjab through fixed plot surveys in Fruit Research Farm, Punjab Agricultural University (PAU), Ludhiana, Punjab during 2018 and 2019 to record the emerging insect pests and their natural enemies. During these surveys, infection of a fungus was observed on the adults of blow fly, Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) occurring on ber plants in PAU, Ludhiana. This fly is economically significant as pollinator of fruit crops. The adult flies were observed to be dead and were covered with fungal mycelial growth. Later on, the fungus was identified as an entomopathogenic fungus, Cladosporium cladosporioides based on morphological and molecular characterization. This is the first record of infection of an entomopathogenic fungus, C. cladosporioides on this pollinator dipteran fly, C. megacephala from Punjab, India. Thus, the potential of C. cladosporioides for the control of other dipteran insect-pests of fruit crops can be explored.

Entrapment of Bradysia paupera (Diptera: Sciaridae) by Phaseolus vulgaris (Fabaceae) plant leaf

Flies of the genus Bradysia (Diptera, Sciaridae) are considered as major insect pests of greenhouse-grown horticultural crops. The ability of hooked trichomes of the French bean Phaseolus vulgaris to impale and entrap herbivorous insects thus resulting in insect reduced longevity, reproduction and larval mortality is well known. The present study investigates under laboratory conditions the ability of hooked trichomes of bean leaves to entrap fungus gnats Bradysia paupera, in order to estimate the reduction of their population. We characterized the entrapment mechanism of hooked trichomes towards B. paupera using cryo-scanning electron microscopy, and evaluated the silicon distribution in hooked trichomes with the energy dispersive X-ray microanalysis. We evaluated the trapping efficiency of hooked trichomes in fertilized and unfertilized bean plants towards B. paupera, in comparison with insects feeding on the plant leaf such as black bean aphid Aphis fabae and young stages of the southern green stinkbug Nezara viridula. For B. paupera, we recorded about 30% of entrapped insects in unfertilized plants. Considering the number of entrapped insects in relation to the leaf surface, the percentage of entrapped insect was higher in unfertilized than in fertilized plants having lower density of hooked trichomes. The presence of P. vulgaris plants in greenhouses could represent a useful method in integrated pest management to reduce Bradysia spp. population.

Improving ecological fitness of Beauveria bassiana conidia to control the sugar cane borer Diatraea saccharalis

ABSTRACTDiatraea species are considered the most important insect pests in sugarcane crops in Colombia and other South America countries. Previous research demonstrated Beauveria bassiana isolate Bv062 to be pathogenic to larvae of Diatraea species under laboratory conditions. However, virulence of the isolate was variable, possibly affected by inoculum quality. The aim of this research was to select an appropriate mass culture medium to produce conidia with consistently high yield, high virulence, and high storage stability. Conidia were produced on three semi-solid media based on rice, oat and potato, which were adjusted to three levels of water activity (aw). Conidia yield, germination, polyols accumulation, enzymatic activity, and virulence to Diatraea saccharalis larvae, before and after 30 days of storage at 30°C, were measured. Conidia produced on potato-based medium were the most virulent, with a median lethal time (LT50) of 8.9 days, compared to 9.7 and 9.1 days for rice and oat media, respectively. Insecticidal activity was stable after one month of storage for conidia produced on potato (LT50 8.0 days) but was reduced for conidia produced on the other media (LT50 13.0 days and 11.7 days for rice and oat, respectively). Mannitol was the predominant polyol in conidia and trehalose was not detected. Maximum yield and storage stability were obtained in the potato-based medium (C:N ratio of 30:1). Based on these results, potato-based medium is superior to the standard rice-based medium for the production of B. bassiana Bv062 conidia with better ecophysiological performance to control the sugar cane borer.