Major Natural Enemies Research Articles

Population Dynamics of Major Insect Pests and Natural Enemies in Tomato

An experiment on major insect pests and natural enemies of tomato was conducted during rabi, 2022-23 at the experimental farm for PG research, Biswanath College of Agriculture, Sonitpur. Results revealed eleven insect pests; whitefly, Bemisia tabaci (Gennadius); aphid, Aphis craccivora Koch; leafminer, Lyriomyza trifolii (Burgess); fruitborer, Helicoverpa armigera (Hubner); jassid, Amrasca biguttula biguttula (Ishida); semilooper, Trichoplusia ni (Hubner) were found to be the most dominant species. Two coccinellid predators viz., Micraspis discolor(F) and Cheilomenes sexmaculata (F) and two spiders Lycosa tista Tikader, Anyphaena accentuata (Walckenaer) were recorded as natural enemies. It was observed that the incidence of B. tabaci, A. craccivora and A. biguttula biguttula showed significant negative correlation with both maximum and minimum temperature. B. tabaci population registered a positive significant correlation with morning relative humidity. Both L. trifolii and H. armigera exhibited significant negative correlation with bright sunshine hour. Furthermore, T. ni showed significant negative correlation with maximum temperature and bright sunshine hour. As regards coccinellids, a significant negative correlation existed with maximum and minimum temperature, and rainfall and significant positive correlation with morning relative humidity. A significant positive correlation of aphids was also observed with coccinellids.

Evaluation of different plant products against pod borer, Helicoverpa armigera (Hubner) infesting chickpea under certified organic farming system

Pest management under organic farming is a challenging task, wherein, ecofriendly approaches against insect pest were accomplished through the use of appropriate strategies which promotes manipulation and alteration of agro-ecosystem. In this view, an experiment was laid out in Randomized Block Design with JG-11, a chickpea variety sown during rabi of 2021-22 and 2022-23 at certified organic block (certified since 2006), Bio-Resource Farm, Institute of Organic Farming, University of Agricultural Sciences, Dharwad. The analysis of pooled data for two seasons revealed that, among various plant products evaluated the plots treated with NSKE @ 5% found superior with significantly least larval population of Helicoverpa armigera (0.72 larvae/m row), with minimum per cent defoliation (12.02%) as well as significantly lower pod damage (11.75%) which was followed by Vitex negundo @ 5%. Similarly, statistically higher chickpea yield was noticed under plots sprayed with NSKE @ 5% with (825.40 kg/ha) with B:C ratio (1.77) during 2021-22, and (788.36 kg/ha) with B:C ratio of (1.69) during 2022-23, compared to untreated check with 161.02 kg/ha and 195.77 kg/ha during 2021-22 and 2022-23, respectively. However, in comparison with inorganic check, organically treated plots documented, relatively higher population of major natural enemies of chickpea ecosystem such as Campoletis chlorideae and coccinellids which was on par with untreated control.

Nanoparticle-delivered RNAi-based pesticide target screening for the rice pest white-backed planthopper and risk assessment for a natural predator

Vacuolar-type (H+)-ATPase (vATPase) is a conserved multi-subunit eukaryotic enzyme composed of 14 subunits that form a functional complex consisting of an ATP-hydrolytic domain (V1) and a proton-translocation domain (V0). ATP hydrolysis and subsequent H+ translocation rely heavily on a fully assembled V1/V0 complex. Since vATPase is crucial for insect survival, it is a viable molecular target for pest control. However, detailed functional analyses of the 14 subunits and their suitability for pest control have not been fully explored in a single insect species. In this study, we identified 22 vATPase subunit transcripts that correspond to 13 subunits (A1, A2, B, C, D, E, F, G, H, a1, a2, c and d) in the white-backed planthopper (WBPH), Sogatella furcifera, a major hemipteran pest of rice. RNAi screens using microinjection and spray-based methods revealed that the SfVHA-F, SfVHA-a2 and SfVHA-c2 subunits are critical. Furthermore, star polymer (SPc) nanoparticles were utilized to conduct spray-induced and nanoparticle-delivered gene silencing (SI-NDGS) to evaluate the pest control efficacy of RNAi targeting the SfVHA-F, SfVHA-a2 and SfVHA-c2 transcripts. Target mRNA levels and vATPase enzymatic activity were both reduced. Honeydew excreta was likewise reduced in WBPH treated with dsRNAs targeting SfVHA-F, SfVHA-a2 and SfVHA-c2. To assess the environmental safety of the nanoparticle-wrapped dsRNAs, Cyrtorhinus lividipennis Reuter, a major natural enemy of planthoppers, was also sprayed with dsRNAs targeting SfVHA-F, SfVHA-a2 and SfVHA-c2. Post-spray effects of dsSfVHA-a2 and dsSfVHA-c2 on C. lividipennis were innocuous. This study identifies SfVHA-a2 and SfVHA-c2 as promising targets for biorational control of WBPH and lays the foundation for developing environment-friendly RNAi biopesticides.

Niche Study of Major Pests and Natural Enemies in Peach Orchards with Different Vegetative Ground Covers

Abstract As a modern orchard management tool, vegetative ground cover can increase biodiversity, enhance the effect of natural enemies, and reduce the amounts of chemical agents used to control pests. This study aimed to investigate the temporal niche relationship between pests and natural enemies in peach orchards (1) planted with flowering plants as a ground cover or (2) with naturally occurring vegetative ground cover or (3) plowed, with the objective of clarifying the conservation effect of peach orchard ground cover on different natural enemies. The results showed that the niche width value of natural enemies in peach orchards planted with the flowering plants was the highest, followed by natural vegetation peach orchards. The ladybird beetle (Coccinellidae) ecological niche width values were the highest in the natural enemy communities of the two types of peach orchards. These results demonstrate that vegetative ground cover in peach orchards can effectively harbor natural enemies and that coccinellids are highly adapted for the ecological environment of the peach orchard.

Indirect and direct interactions between grain aphid and parasitoid in the presence of symbiont Regiella insecticola

BackgroundAphids often harbor bacterial symbionts that confer resistance to biotic and abiotic stress. Previous studies have primarily examined the direct effects of symbiont infection on parasitoid success but less on aphid population dynamics under indirect parasitic situations, for example when exposed to parasitoid wasp odor. Deciphering this type of indirect effect is essential for understanding dynamics of insect ecosystems and communities and to improve IPM success.MethodsWe generated Sitobion avenae aphid clonal lines that are genetically identical but differ in Regiella insecticola infection. Then, the indirect odor effect of female parasitoid wasp Aphidius gifuensis (Ashmaed), one of its major natural enemies in the fields, was examined on the aphid lines fitness using different parasitoid densities. With these lines we also tested the direct effect of symbiont presence on aphid resistance against different parasitoid densities.ResultsOur study found fitness costs for the aphid line hosting Regiella, mainly via an increase in the development time and a reduction in population increase rate. Some of these fitness traits were influenced by the indirect exposure to parasitoid wasp odor with a density effect. Presence of the symbiont also reduced A. gifuensis parasitic success, increased the wasp development time and decreased its emergence weight with low effect of the parasitoid density used for parasitism.ConclusionsThese results showed that aphid population dynamic was mainly affected by the symbiont presence, but not by parasitoid odor. Symbiont presence also protected aphid from parasitism and affected parasitoid offspring weight and hence their future individual fertility and fitness.

Influence of Silicic Acid Foliar Spray on the Incidence of Sucking Insect Pests and their Natural Enemies in Rapeseed

Silicon induces resistance in various crops against insect pests of diverse feeding guilds, including hemipterans, through upregulation of plant defense mechanisms along with maintenance of plant physiological processes. The present investigation to study the effect of silicon in the form of silicic acid (SA) against major sucking insect pests (Lipaphis erysimi and Bagrada hilaris) and natural enemies (Coccinella transversalis and Episyrphus balteatus) in rapeseed revealed that the foliar application of SA @ 0.4% thrice at 30, 40 and 50 days after sowing significantly reduced the colonization of L. erysimi as against non-significant effect on the population of B. hilaris. Three sprays of SA @ 0.4% significantly increased the population of C. transversalis without any significant effect on E. balteatus population. The silicon content of the rapeseed grains was also found to be significantly enhanced (0.32%) with 3 sprays of SA @ 0.4%.

Predatorska stenica Nesidiocoris tenuis (Heteroptera: Miridae), prirodni neprijatelj štetnih insekta u plasteničkoj proizvodnji paradajza

Species of zoophytophagous genus Dicyphina, plant bugs (Hemiptera: Miridae: Bryocorinae) are among the most abundant and effective predators of tomato pests. Nesidiocoris tenuis Reuter, 1895 (Hemiptera: Miridae) is the predominant species of Dicyphina sp. and it is considered to be a major natural enemy of insect pests in tomato crops in the Mediterranean region. This predatory bug is proved to be particularly successful in suppressing Tuta absoluta Meadow, 1917 (Lepidoptera: Gelechiidae), a major pest of tomato in greenhouse production. Aims of the study were to 1) investigate the efficiency of the mirid predatory bug N. tenuis in greenhouse tomato production and 2) to estimate the possibilities of its application in commercial vegetable production in Western Balkan countries of Europe. The significance of the study results relies on the possibility of commercialisation and general promotion of biological agent N. tenuis in tomato production in South East part of Europe, where the usage of pesticides still dominates the field of plant protection, both in vegetables and other agricultural sectors. According to the obtained results, the biological agent N. tenuis represents a reliable tool for controlling the level of the tomato leaf miner population by keeping the pest below its economic and intervention threshold.

Aphid Pest Management in Sweet Pepper Field with Rapeseed as a Companion Crop

Sweet pepper, Capsicum annum L. is commercially grown vegetable grown for its nutritional and economical value. Sucking pests like aphids, whiteflies, thrips, mites, etc. are the major insect pest in sweet pepper fields. Farmers deliberately have been using chemical pesticides in their crop to manage various insect pest and such practices of using hazardous chemicals are harmful to human health and the biodiversity. Similarly, farmers don't have an idea of planting trap and/or companion plants and its role in natural control of pest. Hence, a study was conducted to know the population dynamics, especially to assess the aphid (Myzus persicae, Sulzer) population and its potential natural enemies by planting rapeseed as companion crop. This field experiment was conducted in six different locations of Bharatpur-23, Chitwan from Nov 2019 to Jan 2020 where three plots of sweet pepper were planted with rapeseed as companion crop and other three plots solely having no floral source around. Aphid population was recorded at weekly interval and its major natural enemies; ladybird beetle and syrphid fly. Abnormal data were squared root transformed and analyzed by using paired sample t-test. The result showed that the aphid population in sweet pepper field with companion crop was significantly lower than in sweet pepper grown without floral source (control). Highly significant number of ladybird beetles and syrphid flies were recorded in sweet pepper with companion crop compared to control. The finding is helpful to develop an integrated management protocol of sweet pepper pests with the practice of following conservation biological control strategy.

Combining organic and conservation agriculture to restore biodiversity? Insights from innovative farms in Belgium and their impacts on carabids and spiders

Conservation and organic agriculture are two alternative crop management strategies associated with environmental impact reduction, leading theoretically to more biodiversity and higher ecological functioning, underpinning better ecosystem service delivery. The combination of these two farming strategies is increasingly seen as an opportunity to mitigate shortcomings of each of them taken individually. However, combining organic and conservation agriculture is undeniably challenging, since it leaves nocurativeoption (neither synthetic pesticides nor soil plowing) for pest control (phytophagous, pathogens, and weeds). Hence, the latter must be ensured by effective restoration of predatory communities. The present research investigated the potential of combining organic and conservation agriculture to support two major ground-dwelling natural enemy communities: carabids and spiders. We used pitfall traps to sample these two communities in paired adjacent cereal fields conducted under organic-conservation (OC) and conventional (CV) agriculture in Belgium. Community assemblages were significantly different across system types, both in terms of species diversity and functional trait diversity. OC parcels showed higher alpha and beta species diversities for both carabids and spiders and species composition differed between OC and CV parcels. OC systems were associated with higher variation of species assemblages among parcels than CV systems Functional traits also differed across system types for both groups. We found more herbivorous and granivore carabids in OC parcels, and more predator species in CV parcels. We found larger spiders, more hunting spiders and more wetland spiders in OC parcels, whereas we found more web weavers and more forest spiders in CV ones. Functional diversity was higher in OC parcels for carabids, but not for spiders. In brief, OC parcels supported more diverse communities, both taxonomically and functionally. These outcomes show that OC systems are promising systems to support these natural enemy communities. Further studies should assess whether combining organic and conservation agricultural enables sufficient pest control levels to achieve high levels of food production and farmers income.

Sublethal and transgenerational effects of exposures to the thiamethoxam on the seven-spotted lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

The seven-spot ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae) has been used as the major natural enemy insect against many kinds of aphids in environment. Thiamethoxam is a second-generation neonicotinoid insecticide and commonly used to control various aphids, but it also has adverse effects on natural enemies. Therefore, the sublethal effects of thiamethoxam on the offspring of C. septempunctata were studied. For the adults of C. septempunctata, the LD30 of F0, F5, F10 and F15 generations were 0.039, 0.136, 0.243, 0.417 μg adult−1, respectively. The LD50 of F0, F5, F10 and F15 generations were 0.072, 0.275, 0.435, 0.819 μg adult−1, respectively. The resistance ratio of the F15 generation was 11.4-fold higher than that of the F0 generation. The preadult duration ( F0 = 17.4 d, F5 = 20.0 d, F10 = 19.1 d, F15 = 18.0 d) and adult preoviposition period ( F0 = 7.39 d, F5 = 8.07 d, F10 = 9.32 d, F15 = 8.03 d) of C. septempunctata were prolonged, and the fecundity ( F0 = 1690.10, F5 =1686.93, F10 = 1119.40, F15 = 752.87), oviposition period ( F0 = 42.84 d, F5 =40.33 d, F10 = 40.72 d, F15 = 30.84 d) and total longevity ( F0 = 86.7 d, F5 =81.3 d, F10 = 82.0 d, F15 = 74.0 d) were reduced by long-term exposure to sublethal dosage (LD30) of thiamethoxam. Population parameters (r, λ, R0, and T) were significantly reduced in F5, F10 and F15 generation. In addition, the predation function of F15 generation was reduced by sublethal dosage exposure of thiamethoxam. These results showed the negative impacts of sublethal thiamethoxam on the offspring of predators.

Comparative efficacies of modules against major insect pests and natural enemies in rice (Oryza sativa)

A field experiment was conducted at regional Research and Technology Transfer Station (OUAT), Chiplima,Sambalpur, Odisha, during rainy season (kharif) 2019–20 to determine the comparative efficacies of variousinsecticides and botanicals modules against major insect pests and natural enemies of rice (Oryza sativa L.). Therewere 9 modules and overall data revealed that the all the treated plots recorded significantly lower per cent of deadheart; white ear-head caused by stem borer; silver shoot caused by gall midge; leaf folder infested leaves and planthoppers. Among them, module consists of fipronil 5 sc @1500 ml/ha at 25–30 DAT, rynaxypyr 20 sc @150 ml/ha at45–50 DAT and triflumezopyrim 106 sc @240 ml/ha at 65–70 DAT treated plot recorded significantly higher per centreduction of stem borer infestation, leaf folder, plant hoppers and produced higher grain yield than the other modules as well as highest benefit cost ratio B : C (1.89) and next best was carbosulfan 25 ec @875 ml/ha, rynaxypyr 20 sc @150 ml/ha and flonicamid 50 wg @150 g/ha containing module. So, the module containing fipronil, rynaxypyr and triflumezopyrim may be adopted for the effective management of major insect pests of rice and helps the farmers from unwanted spraying of insecticides many times.

Multi-scale approach to biodiversity proxies of biological control service in European farmlands

Intensive agriculture has profoundly altered biodiversity and trophic relationships in agricultural landscapes, leading to the deterioration of many ecosystem services such as pollination or biological control. Information on which spatio-temporal factors are simultaneously affecting crop pests and their natural enemies is required to improve conservation biological control practices. We conducted a study in 80 winter wheat crop fields distributed in three regions of North-western Europe (Brittany, Hauts-de-France and Wallonia), along intra-regional gradients of landscape complexity. Five taxa of major crop pests (aphids and slugs) and natural enemies (spiders, carabids, and parasitoids) were sampled three times a year, for two consecutive years. We analysed the influence of regional (meteorology), landscape (structure in both the years n and n-1) and local factors (hedge or grass strip field boundaries, and distance to boundary) on the abundance and species richness of crop-dwelling organisms, as proxies of the service/disservice they provide. Firstly, there was higher biocontrol potential in areas with mild winter climatic conditions. Secondly, natural enemy communities were less diverse and had lower abundances in landscapes with high crop and wooded continuities (sum of interconnected crop or wood surfaces), contrary to slugs and aphids. Finally, field boundaries with grass strips were more favourable to spiders and carabids than boundaries formed by hedges, while the opposite was found for crop pests, with the latter being less abundant towards the centre of the fields. We also revealed temporal modulation—and sometimes reversion—of the impact of local elements on crop biodiversity. To some extent, these results cause controversy because they show that hedgerows and woodlots should not be the unique cornerstones of agro-ecological landscape design strategies. We point out that combining woody and grassy habitats to take full advantage of the features and ecosystem services they both provide (biological pest control, windbreak effect, soil stabilization) may promote sustainable agricultural ecosystems. It may be possible to both reduce pest pressure and promote natural enemies by accounting for taxa-specific antagonistic responses to multi-scale environmental characteristics.

A Review of Franklinothrips vespiformis (Thysanoptera: Aeolothripidae): Life History, Distribution, and Prospects as a Biological Control Agent.

Simple SummaryPredatory species are a small but significant part of the Thysanoptera, which is often overlooked. Franklinothrips are found throughout the tropics and are regarded as major natural enemies of thrips and other small arthropod prey. In this review, we summarized the geographical background, morphology, and prey associations, with an emphasis on Franklinothrips vespiformis, the most widely distributed predatory thrips species. This literature review could serve as a foundation for future research into Franklinothrips as biocontrol agents for economically important insect and mite pests in China.Predatory species comprise a small but important and often overlooked component of the Thysanoptera. A case in point, the ant-mimicking Franklinothrips are widely distributed in the tropics and are considered important generalist natural enemies for thrips and some other small arthropod prey. Franklinothrips present an addition to biocontrol applications, i.e., greenhouse or commercial application for certain target pests and situations. Current knowledge, including distribution, biological features, life history pa rameters, prey specificity, host plant associations and lass production is yet insufficient to decide to what extent Franklinothrips could contribute for biological control programs. In this review, we summarized the geographical background, morphology, and prey associations, with a focus on F. vespiformis, the most widely distributed species of predatory thrips. This literature review serves as the basis for future research into the use of Franklinothrips as biocontrol agents for economically significant insect and mite pests in China and elsewhere.

Unexpected parasitism of Douglas-fir seed chalcid limits biocontrol options for invasive Douglas-fir in New Zealand

Douglas-fir seed chalcid (DFSC) Megastigmus spermotrophus, a small (3 mm long) host-specific seed-predatory wasp, was accidentally introduced into New Zealand in the 1920s. Concern over DFSC reducing Douglas-fir seed production in New Zealand led to an attempt at biocontrol in 1955 with the release, but failed establishment, of the small (2.5 mm long) parasitoid wasp, Mesopolobus spermotrophus. We investigated why DFSC causes little destruction of Douglas-fir seed in New Zealand (usually <20%) despite the apparent absence of major natural enemies. Douglas-fir seed collections from 13 New Zealand sites yielded the seed predator (DFSC) but also potential parasitoids, which were identified using morphology and partial COI DNA sequencing. DFSC destroyed only 0.15% of Douglas-fir seed. All parasitoids were identified as the pteromalid wasp, Mes. spermotrophus, the host-specific biocontrol agent released in 1955. Total parasitism was 48.5%, but levels at some sites approached 90%, with some evidence of density-dependence. The discovery of the parasitoid Mes. spermotrophus could indicate that the biocontrol agent released in 1955 did establish after all. Alternatively, Mes. spermotrophus could have arrived accidentally in more recent importations of Douglas-fir seed. The high level of parasitism of DFSC by Mes. spermotrophus is consistent with DFSC being under successful biological control in New Zealand. Suppression of DFSC populations will benefit commercial Douglas-fir seed production in New Zealand, but it also represents the likely loss of a potential biological control agent for wilding Douglas-fir.

Damage, distribution and natural enemies of invasive fall armyworm Spodoptera frugiperda (J. E. smith) under rainfed maize in Karnataka, India

Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a polyphagous pest invaded India and seriously threatened maize and other crops. The detailed information on its occurrence and damage severity in the invaded regions are limited. In this study, we assessed the occurrence, incidence and damage severity of fall armyworm in 126 maize fields in 10 districts of Karnataka during the rainfed condition. Further, potential co-occurrence of this pest with native stem borers and its natural enemies explored to tackle this pest. Survey reports revealed that the fall armyworm was well distributed across the maize growing regions of Karnataka with 44–100% field infestation. The damage incidence of S. frugiperda was 22.13–46.83% with damage severity 0 to 4.9 on the 0 to 9 scale. The larval count was 0.93 ± 0.17 to 3.07 ± 0.58 per 10 plants across the locations. The co-occurrence of S. frugiperda with the native maize stem borers, Chilo partellus (Swinhoe) and Sesamia inferens (Walker) was less than 5% of the plants. It shows that S. frugiperda had dominated the native stem borers causing significant damage to maize. This study found five parasitoids parasitizing the egg, egg-larval, larval and larval-pupal stages of S. frugiperda. Trichogramma chilonis Ishii and Telenomus remus Nixon egg parasitism rates were 15.81–23.87% and 5.44–8.78%, respectively. The larval parasitoids caused 9.18% parasitism of S. frugiperda larvae. Trichogramma chilonis appeared as a major natural enemy. These data provide an important baseline for the development of sustainable management strategies for S. frugiperda.

A Bioclimate-Based Maximum Entropy Model for Comperiella calauanica Barrion, Almarinez and Amalin (Hymenoptera: Encyrtidae) in the Philippines.

Simple SummaryThe discovery of Comperiella calauanica a parasitoid confirmed to be the major natural enemy of the invasive diaspidid, Aspidiotus rigidus, has led to the promise of biological control in sustainable pest management of this devastating coconut pest. In this study, we employed Maximum Entropy (Maxent) to develop a bioclimate-based species distribution model (SDM) for the parasitoid from presence-only data recorded from field surveys conducted in select points the Philippines. Results of assessment of the generated model point to its excellent power in predicting either suitability of habitat, or potential occurrence or distribution of C. calauanica. Since the parasitoid is highly host-specific, the model may also apply to A. rigidus. Field surveys in select areas in the Philippines confirmed the occurrence of the invasive coconut scale in areas predicted by the model as having considerable probability of occurrence, or habitat suitability. Our findings strongly suggest the potential utility of Maxent SDMs as tools for pest invasion forecasting and GIS-aided surveillance for integrated pest management (IPM).Comperiella calauanica is a host-specific endoparasitoid and effective biological control agent of the diaspidid Aspidiotus rigidus, whose outbreak from 2010 to 2015 severely threatened the coconut industry in the Philippines. Using the maximum entropy (Maxent) algorithm, we developed a species distribution model (SDM) for C. calauanica based on 19 bioclimatic variables, using occurrence data obtained mostly from field surveys conducted in A. rigidus-infested areas in Luzon Island from 2014 to 2016. The calculated the area under the ROC curve (AUC) values for the model were very high (0.966, standard deviation = 0.005), indicating the model’s high predictive power. Precipitation seasonality was found to have the highest relative contribution to model development. Response curves produced by Maxent suggested the positive influence of mean temperature of the driest quarter, and negative influence of precipitation of the driest and coldest quarters on habitat suitability. Given that C. calauanica has been found to always occur with A. rigidus in Luzon Island due to high host-specificity, the SDM for the parasitoid may also be considered and used as a predictive model for its host. This was confirmed through field surveys conducted between late 2016 and early 2018, which found and confirmed the occurrence of A. rigidus in three areas predicted by the SDM to have moderate to high habitat suitability or probability of occurrence of C. calauanica: Zamboanga City in Mindanao; Isabela City in Basilan Island; and Tablas Island in Romblon. This validation in the field demonstrated the utility of the bioclimate-based SDM for C. calauanica in predicting habitat suitability or probability of occurrence of A. rigidus in the Philippines.

Biodiversity and Population Dynamics of Natural Enemies in the Western Desert Agro-Ecosystem, Egypt

Extension of the newly reclaimed areas for agriculture in Egypt has obviously affected the microclimate of the insect pests, which seriously threatens the cultivated field crops. Besides, the role of the major natural enemies must be carefully understood. Therefore, a field study was conducted in El-Farafra Oasis, Western Desert, Egypt to assess biodiversity and population dynamics of major natural enemies found associated with three field crops (faba bean, cotton, and alfalfa) by sweep-net and beat and shake sampling. The species diversity of natural enemies included 27 species, 23 genera, 14 families belonging to six orders and the total abundance of these species was 5098 individuals sampled during 2018 and 2019. The most common insect order was Coleoptera (composing 42.2% of the total abundance) followed by Hymenoptera (28.1%) and Neuroptera (17.8%), whereas the smallest number of individuals found in Odonata (2.1%). Similar population dynamics of natural enemies in the three crop fields were observed during the two seasons, and most species showed a positive correlation with temperature and negative correlation with relative humidity. The values of species diversity, richness, and evenness indices were higher in the alfalfa field (2.529, 2.623, and 0.846, respectively).

Correlation the incidence of major insect-pest and natural enemies with weather parameters

Major insect pest of okra viz., jassid (Amrasca bigutulla biguttula), whitefly (Bemisia tabaci), and shoot and fruit borer (Earias vittella) damaged heavily during the kharif. The incidence of leafhopper, whitefly, shoot and fruit borer and natural enemies show correlation with weather parameters, minimum temperature showed significantly positive correlation (r = 0.611* and 0.807**) with jassid incidence during both the year of study. Maximum temperature showed non-significant negative correlation with jassid incidence during 2018 and significantly positive correlation during 2019 and correlation values in respective years were (r= -0.234 and 0.836**). Relative humidity and rainfall showed negative non-significant correlation with Whitefly incidence during both the years and correlation values in respective years were (r= -0.323, -0.092 and r= -0.562, -0.580). Minimum temperature showed positive significant correlation (r= 0.757** and 0.835**) during both the years. Maximum temperature showed non-significant negative correlation with per cent shoot damage during 2018 and significantly positive correlation during 2019 and correlation values in respective years were (r= -0.138 and 0.810**). Whereas, wind speed and sunshine showed positive non-significant correlation (r= 0.040 and 0.171) during first year and negative non-significant correlation (r= -0.373 and -0.064) during second year. minimum temperature and Clubiona sp. showed positive significant correlation (r= 0.438 and 0.493) during both the years.

Incidence of Major Insect Pests and Natural Enemies in Three Rice Growing Seasons of Bangladesh

Incidence of insect pests and their associated natural enemies was investigated from July 2017- June 2018 at six locations (Gazipur, Rajshahi, Barishal, Sonagazi, Rangpur, Cumilla) of Bangladesh to identify their major occurrence period as well as their incidence in three rice growing seasons, (Aus, T. Aman, and Boro). Among the tested locations, marked differences were found in the composition of insect pest and natural enemies. Higher number of pest population was found at Gazipur with 80,000 individuals for insect pest and 40,000 individuals for natural enemies. At least one peak for major insect pest and natural enemies suggested their specific occurrence period across the locations. Among the insect pests, major peak of GLH was found at Gazipur and Rajshahi during T. Aman season with 4,000 individuals for each location. In contrast, BPH population was as high as 10,000 individuals for Gazipur in October during T. Aman season. Additionally, it was high at Rajshahi in October and November with around 2,000 individuals of BPH. For WBPH, one major peak was found in October at Gazipur and Rajshahi with 10,000 and 2,000 individuals respectively. For YSB, it was higher at Rajshahi in October with over 6,000 individuals during T. Aman season. Moreover, one major peak also observed in Barishal with over 2,000 individuals in November. Among natural enemies, CDB population was observed mainly at three locations in between October and November with 900 individuals for Gazipur, 400 individuals for Rajshahi and 200 individuals for Barishal during T. Aman season. In contrast, for STPD population, two major peaks were found in Barishal with 6,000 and 5,000 individuals in December and March respectively during Boro season. For GMB population, it was observed at Gazipur in November with more than 20,000 individuals during T. Aman season whereas Rajshahi had around 2,000 individuals in the same month. However, higher incidence of GLH, BPH, and WBPH at Gazipur and Rajshahi suggested availability of insect pests during T. Aman season. In contrast, higher YSB incidence at Barishal and Rajshahi indicated their abundance in those areas. On the other hand, incidence of natural enemies at Gazipur indicated presence of greater biological control compared with other locations. In future, this information could serve as a reliable source in strengthening rice pest monitoring services as well as effective pest control in Bangladesh.
 Bangladesh Rice j. 2019, 23(1): 35-43

Population dynamics of major insect pests and natural enemies of sunflower

A field study was carried out during 2018-19 to evaluate the population fluctuation of insect pests and their natural enemies in sunflower ecosystem. The data revealed that thrips and lepidopteran pests viz., head borer, Helicoverpa armigera and defoliator pests such as Spodoptera litura and Spilarctia obliqua were found to be the major insect pests during kharif season. Whereas, the sucking pests viz., leafhopper and whiteflies were found to be the major insect pests during rabi season. Among natural enemies, lady beetles, Chrysoperla and spiders were found to be the major predators throughout the crop season.