Insect Natural Enemies Research Articles

Ecological requirements drive the variable responses of wheat pests and natural enemies to the landscape context

Abstract Semi‐natural habitats (SNH) are considered essential for pest‐suppressive landscapes, but their influence on crop pests and natural enemies can be highly variable. Instead of SNH per se, the availability of resources, such as pollen and nectar, may be more relevant for supporting pest control. Here, we assessed the spatiotemporal variation of multiple insect pests (cereal leaf beetles and aphids) and natural enemies (predators and aphid parasitoids) in wheat fields and their responses to landscape context and flower availability. We combined detailed information on pollen use by natural enemies with the specific distribution of pollen‐providing plants across a gradient of landscape composition and configuration. The abundance of wheat pests was tightly linked to wheat development stage. Syrphids colonised the fields early in the season, while the abundance of other enemies increased later in the season. The responses of pests to landscape structure were variable and, while some pests had low abundances in landscapes with high edge density and SNH cover, Sitobion avenae abundance was positively associated with SNH cover. Lacewings, syrphids and cereal leaf beetles were abundant in landscapes with diverse and abundant flower resources, whereas the abundance of parasitoids and Nabis sp. was driven by aphid abundance. We detected no significant indirect effects of landscape on pests via natural enemies. Synthesis and applications. Our findings highlight the need for conservation biological control to go beyond ‘one size fits all’ and consider the specific ecology of the involved organisms, even for a single crop type. Landscapes with high edge density and flowering woody plants may support natural enemies, in particular syrphids, which colonised the fields early in the season. Incentives for pest‐suppressive landscapes should focus on tailored strategies that disfavour dominant cereal pests and simultaneously enhance natural enemies according to their ecological requirements.

The first chromosome-level genome assembly of a green lacewing Chrysopa pallens and its implication for biological control.

Many lacewing species (Insecta: Neuroptera) are important predators of pests with great potential in biological control. So far, there is no chromosome‐level published genome available for Neuroptera. Here we report a high‐quality chromosome‐level reference genome for a green lacewing species Chrysopa pallens (Neuroptera: Chrysopidae), which is one of the most important insect natural enemies used in pest biocontrol. The genome was sequenced using a combination of PacBio and Hi‐C technologies and assembled into seven chromosomes with a total size of 517.21 Mb, occupying 96.07% of the genome sequence. A total of 12,840 protein‐coding genes were identified and approximately 206.21 Mb of repeated sequences were annotated. Phylogenetic analyses indicated that C. pallens diverged from its common ancestor with Tribolium castaneum (Coleoptera) approximately 300 million years ago. The gene families involved in digestion, detoxification, chemoreception, carbohydrate metabolism, immunity, nerves and development were significantly expanded, revealing the potential genomic basis for the polyphagia of C. pallens and its role as an excellent biocontrol agent. This high‐quality genome of C. pallens will provide an important genomic resource for future population genetics, evolutionary and phylogenetic investigations of Chrysopidae as well as comparative genomic studies of Neuropterida and other insects.

Suitability of Hybrid and Landrace Maize Plants Within Conventional and Organic-Polyculture Maize Agroecosystems for Hosting Parasitic Wasps

Abstract Polycultures and conventional monoculture have different effects on insect pests and natural enemies. Little is known about the parasitoid response to landrace and hybrid plants damaged by insect pests within organic-polyculture agroecosystems vs. monoculture ones. The aim of the present study was to compare the suitability of these agroecosystems for hosting parasitic wasps by evaluating the parasitism rate, parasitoid abundance, and species composition on landrace and hybrid maize races within organic-polyculture and conventional maize agroecosystems. This study was performed within the Mesoamerican region where maize was originally domesticated and where the maize insect pest Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae) originated. Maize plants of landrace and hybrid varieties were used to attract egg parasitoids of D. maidis within each of the two agroecosystems; conventional maize monoculture and an organic-polyculture of landrace maize, beans, and squash, which also included weed plants. Four treatments were conducted in this field experiment: 1) landrace-within organic agroecosystem, 2) hybrid-within organic agroecosystem, 3) landrace-within conventional agroecosystem, and 4) hybrid-within conventional agroecosystem. A community of parasitic wasps, of which the micro-wasp Paracentrobia sp. (Hymenoptera: Trichogrammatidae) was the most abundant member, was found attacking the D. maidis eggs in both agroecosystems. The parasitism rate and parasitoid abundance were similar among the four treatments. However, the abundance of parasitoids was greater in the conventional maize monoculture. Bait plants (landrace and hybrid maize) within each agroecosystem did not show differences in either parasitoid abundance or parasitism rate.

Tracing the distribution of natural enemies of non-native invasive eucalypt insect pests in sub-Saharan Africa

Eucalypt forestry in sub-Saharan Africa is challenged by non-native eucalypt-feeding insects. In recent studies, six invasive eucalypt insect pests, namely Blastopsylla occidentalis, Glycaspis brimblecombei, Gonipterus sp.n.2, Leptocybe invasa, Thaumastocoris peregrinus and Ophelimus maskelli were confirmed present in sub-Saharan Africa. We investigated the diversity and distribution of natural enemies of these pests in six countries in the region. Plant parts (leaves, petioles and stem) infested with the insect pests were sampled from multiple sites in each country. The emerged natural enemies were identified using morphological characteristics and DNA sequence data. Nine species of natural enemies were confirmed present in the surveyed countries, namely Anaphes nitens, Closterocerus chamaeleon, Megastigmus sp., M. pretorianensis, Psyllaephagus blastopsyllae, P. bliteus, Quadrastichus mendeli, Selitrichodes kryceri and S. neseri. No natural enemies were found in Ghana and Sierra Leone despite the presence of L. invasa in both of those countries. Interestingly, most of these natural enemies were unintentionally introduced into the surveyed countries. Results of this study showed that both insect pests and natural enemies introduced into one country are likely to affect many other countries in the region. These findings call for a more coordinated approach to the management of plantation pests in the region.

Biological control technology and application based on agricultural unmanned aerial vehicle (UAV) intelligent delivery of insect natural enemies (Trichogramma) carrier.

Agricultural pests and diseases affect grain yield and quality. In addition to the use of chemical agents, the biological control of diseases and insect pests has attracted more and more attention due to an urgent need for environmental protection. However, traditional operational methods do not integrate well with biological control technology. With the advantages of simple operation, low operating cost, high operating efficiency and wide application range, use of multirotor unmanned aerial vehicles (UAVs) in biological control is of great significance. An intelligent delivery system comprising an insect natural enemy (Trichogramma) capsule based on an M45 electric multirotor UAV was built to release Trichogramma ostriniae in corn fields under full autonomous mode. During operation, the M45 UAV can fly accurately in accordance with operational requirements; average deviation between the actual and planned routes was 0.24 m, the average flight speed was 9.18 m s-1 and the average altitude was 5.08 m. The effective coverage rate of natural enemies was 99.33% and the coverage redundancy was 36.75%. After delivery, an investigation into the field control effect showed an average control effect of 83.70%, which can result in effective pest control. A natural enemy carrier intelligent delivery system based on an M45 electric multirotor UAV was found to have good flight performance. In addition, natural enemies were evenly distributed, giving even coverage of the target fields. The system had a good control effect. © 2021 Society of Chemical Industry.

Contact toxicity of a new acaricide, SYP-9625, to the natural predator, Chrysopa pallens

• We first evaluated the contact toxicity of an acaricide, SYP-9625, on C. pallens . • SYP-9625 only had mild detrimental impacts on insect growth and metamorphosis. • SYP-9625 had significant adverse effects on adult survival and Vg expression. • The paper will strengthen the compatibility of acaricide and natural predators. SYP-9625 is a novel acaricide synthesized by using cyenopyrafen as lead compound. It is characterized by high acaricidal activity and low toxicity to mammals and has been widely used in Chinese farming areas. However, to date, the toxicity of SYP-9625 to natural enemy insects remained unclear. Here, we evaluated the effects of SYP-9625 on survival, growth, metamorphosis and reproduction of a common natural predator, Chrysopa pallens . Contact toxicity bioassay revealed that SYP-9625 had no significant detrimental impacts on egg hatchability, larval survival and duration, pupation rate, pupal mass, emergence rate, digestive enzyme activity, reproductive output and offspring quality, but drastically reduced adult survival rate, adult lifespan, secondary follicle size and vitellogenin (Vg) transcripts by 27.8%, 15.4%, 33.4% and 59.4%, respectively, suggesting a low contact toxicity of SYP-9625 to C. pallens . This study will strengthen the compatibility of chemical acaricide and natural enemy insects in integrated pest management.

Microclimate structures communities, predation and herbivory in the High Arctic.

In a warming world, changes in climate may result in species‐level responses as well as changes in community structure through knock‐on effects on ecological interactions such as predation and herbivory. Yet, the links between these responses at different levels are still inadequately understood. Assessing how microclimatic conditions affect each of them at local scales provides information essential for understanding the consequences of macroclimatic changes projected in the future.Focusing on the rapidly changing High Arctic, we examine how a community based on a common resource species (avens, Dryas spp.), a specialist insect herbivore (Sympistis zetterstedtii) and natural enemies of lepidopteran herbivores (parasitoids) varies along a multidimensional microclimatic gradient. We ask (a) how parasitoid community composition varies with local abiotic conditions, (b) how the community‐level response of parasitoids is linked to species‐specific traits (koino‐ or idiobiont life cycle strategy and phenology) and (c) whether the effects of varying abiotic conditions extend to interaction outcomes (parasitism rates on the focal herbivore and realized herbivory rates).We recorded the local communities of parasitoids, herbivory rates on Dryas flowers and parasitism rates in Sympistis larvae at 20 sites along a mountain slope. For linking community‐level responses to microclimatic conditions with parasitoid traits, we used joint species distribution modelling. We then assessed whether the same abiotic variables also affect parasitism and herbivory rates, by applying generalized linear and additive mixed models.We find that parasitism strategy and phenology explain local variation in parasitoid community structure. Parasitoids with a koinobiont strategy preferred high‐elevation sites with higher summer temperatures or sites with earlier snowmelt and lower humidity. Species of earlier phenology occurred with higher incidence at sites with cooler summer temperatures or later snowmelt. Microclimatic effects also extend to parasitism and herbivory, with an increase in the parasitism rates of the main herbivore S. zetterstedtii with higher temperature and lower humidity, and a matching increase in herbivory rates.Our results show that microclimatic variation is a strong driver of local community structure, species interactions and interaction outcomes in Arctic ecosystems. In view of ongoing climate change, these results predict that macroclimatic changes will profoundly affect arctic communities.

Abundance and diversity of arthropods in transgenic Bt and non-Bt cotton fields under Indian conditions

Two-year field studies during Kharif 2015 and 2016 were conducted to assess the abundance and diversity of arthropod communities of Bt cotton carrying Cry1Ac and Cry2Ab proteins and non-Bt cotton under sprayed and unsprayed conditions. The experiment was conducted in a randomized block design with four treatments of BG-II and non-Bt cotton. The treatments were non- transgenic cotton with no insecticide treatment, non-transgenic cotton with insecticide treatment, transgenic cotton with no insecticide treatment and transgenic cotton with an insecticide treatment. Arthropod community categorized as target insect pests, sucking insect pests, natural enemies and non-target insects were recorded at different phases of the cotton crop. The sucking insect pests contributed the highest abundance among the total arthropods recorded during the period of study. The abundance and diversity of bollworms that were recorded from non-Bt cotton only suggested effectiveness of BG II cotton against target insect pests. The abundance, species richness and diversity indices with respect to populations of beneficial predaceous arthropods and non-target insects were similar in BG-II and its non-Bt counterpart under unsprayed conditions. On the contrary, these parameters were significantly on the lower side under sprayed regimes for both genotypes. The spray of insecticides in early season against sucking insect pests significantly reduced their abundance and diversity indices in both BGII and non-Bt cotton. As monocropping of BG-II cotton is common on large parts of India, there is a need to monitor the populations of non-target insect species with special emphasis on sucking insect pests on a continuous basis to understand the long-term impact of Bt crops on insect biodiversity for sustainable integrated pest management practices.

Side Effects of Lambda Cyhalothrin and Thiamethoxam on Insect Pests and Natural Enemies Associated with Cotton

Side Effects of Lambda Cyhalothrin and Thiamethoxam on Insect Pests and Natural Enemies Associated with Cotton

Diversity of sarcosaprophagous Diptera (Calliphoridae, Sarcophagidae) in organic and conventional mango plantations in the Brazilian semi-arid region

Increase on intensive monocultures is an important threat to Caatinga biodiversity decrease. The use of chemical insecticides directly affects insect natural enemies of crops, but also non-target species. We aimed to test whether the diversity of sarcosaprophagous flies would be affected by agricultural management (conventional and organic). Adult dipterans were collected monthly, from July 2015 to January 2016, using a grid composed of 12 suspended traps distant 20 m from each other, baited with 150 g of sardine or bovine spleen, in each type of management. We first calculated α-diversity by Hill numbers, then evaluated the difference of diversity metrics by ANOVA. We also graphically visualise the species composition distribution by NMDS. We recorded a total of 4,651 specimens of 15 Calliphoridae and Sarcophagidae species. Chrysomya spp. were the dominant species (93.7% of all blowflies). Sarcophagidae species were sampled in low abundance, but with exclusive presence of some species in each treatment (e.g. B laesoxipha stallengi and Ravinia belforti in organic management). Although there was no difference on sarcosaprophagous fly diversity between treatments, we demonstrate empirically that mango plantations in the Caatinga harbour diverse and abundant assemblages of sarcosaprophagous dipterans, whose richness of species is comparable to other ecosystems such as rainforests and urban areas. Our results expand the known geographical range for forensically relevant species by providing a checklist of sarcosaprophagous dipterans that can thrive in agroecosystems in the Caatinga and, potentially, colonize cadavers disposed in that type of environment.

Diversity, Abundance, and Distribution Patterns of Natural Enemy Insects on Chili (Capsicum annum L.) in Bincau Village, Banjar Regency, South Kalimantan

Chili is a widely cultivated plant by the community because of its profit. Currently, in maintaining the quality of chili, people commonly use a lot of pesticides. In contrast, naturally, there are biological agents in the shape of natural enemy insects, more effective, and environmentally friendly. This study aims to determine the diversity, abundance, and distribution patterns of natural enemy insects in chili plantation (Capsicum annum L.) at Bincau Village, Martapura District, Banjar Regency, South Kalimantan. The sample is collected by pitfall trap, yellow pan trap, and sweep net method. Obtained data are analyzed by Shannon Wienner index (H'), Meyer abundance index, Morisita index (Id), and PCA method for environmental parameter analysis. The results showed the diversity of natural enemy insects on chili plants was moderate (H' = 2.396). Furthermore, the highest abundance in research is demonstrated on Hymenoptera order, which consisted of 9 families, 16 species, and 1,009 individuals. The distribution pattern of natural enemy insects in chili plantations is clustered (Id > 1). Based on the PCA analysis method, the temperature has the most impact on natural enemy insects' presence in this study.

Beyond the Headlines: The Influence of Insurance Pest Management on an Unseen, Silent Entomological Majority

For most of the last two decades, insect pest management in key grain and oilseed crops has relied heavily on an insurance-based approach. This approach mandates a suite of management tactics prior to planting and in the absence of pest data. Because there is little flexibility for using these tactics individually, most producers have adopted this full suite of practices despite mounting evidence that some components do not provide consistent benefits. In North America in particular, this preventive approach to insect pest management has led to steep increases in use of neonicotinoid insecticides and subsequent increases in neonicotinoids in soil and water within crop fields and beyond. These increases have been accompanied by a host of non-target effects that have been most clearly studied in pollinators and insect natural enemies. Less attention has been given to the effects of this practice upon the many thousands of aquatic insect species that are often cryptic and offer negligible, or undefined, clear benefits to humans and their commerce. A survey of the literature reveals that the non-target effects of neonicotinoids upon these aquatic species are often as serious as for terrestrial species, and more difficult to address. By focusing upon charismatic insect species that provide clearly defined services, we are likely dramatically under-estimating the effects of neonicotinoids upon the wider environment. Given the mounting evidence base demonstrating that the pest management and crop yield benefits of this approach are negligible, we advocate for a return to largely-abandoned IPM principles as a readily accessible alternative path.

Diversity and Abundance of Insect in Conventional Apple (Malus sylvestris (L.) Mill) Plantation at Kota Batu, East Java

Apple is a plant that susceptible toward pests and diseases. Application of pesticide to suppress insect pest population gave negative impact toward natural enemies and insect pollinators. The purpose of this research was to determine the diversity and dominance of insect pests, pollinators, and natural enemies of each phase of apple plant development in conventional plantations in Kota Batu, East Java. This research was conducted in February to May 2016 in each phase of apple growth namely, after defoliation, early flower, late flower, early fruit, and late fruit. Plot size was 10x10 m2 with total 5 plots and total plants in each plot were 60 trees. Collection methods were active collection (hand picking, insect net, and beating tray) and passive collection (yellow trap, pitfall trap, light trap, and stainer trap). Preservation methods used in this research were dry preservatoin and wet preservation. Identification was conducted in Laboratorium of Entomology, Faculty of Biology UGM and Laboratorium Entomology, Zoology Division, Research Centre for Biology Indonesian Institute of Sciences, Cibinong. Data analyzed by using Shannon-Wiener Diversity Index, Simpson Dominance Index and Abundance Formulation. The results showed that total insects that was caught consist of 38 species belong to 9 orders. Diversity index in each phase of apple growth were: after defoliation (0.69), early flower (1.39), late flower (1.86), early fruit (0.66), and late fruit (1.24). Domination index each phase of apple growth were after defoliation (0.50), early flower (0.34), late flower (0.21), early fruit (0.75), and late fruit (0.40). Diversity index of potential insect as pest (1.46), as pollinator (1.29), and as natural enemies (1.18). The highest abundance of insect as pollinator was Apis cerana, as natural enemy was Pantala flavescens, and as pest was Aphis gossypii.

Morphological and molecular identification of Xylocoris flavipes (Hemiptera: Anthocoridae) in southern China

Abstract During the investigation of natural enemy insects in grain depots, we've found an Anthocoridae insect accounted for a high proportion of natural enemy insects. We identify the enemy insects from morphology and molecular biology, so as to realize more accurate and effective control of storage pests by using the enemy insect. The images of the insects under the ultra-depth microscope (VHX-5000) showed that the insect adults were black brown in colour; the antennas of both the female and male had four segments, which increase in length sequentially from the base to the end, and had a length of 756.2 μm for the female and 741.1 μm for the male. The rostrums of both the female and the male insects were composed of three segments, the male's rostrum (596.8 μm) were shorter than the female's (734.6 μm), and the former two segments of the female's rostrum were significantly longer than the male's. The abdomen of the insect was bilaterally symmetrical, the female's abdomen was wider than the male, and the male insect had a dent between its eighth and ninth segments of the left abdomen, in which its male genitalia was located. In addition, the nymphs as a whole were tangerine in colour, and the eggs were elliptic with creamy white gloss and gridding patterns on the surface. The cytochrome C oxidase I (COI) gene sequences of the insects were identified by DNA barcoding technique, and the determined COI sequences were then submitted to the Genbank database for Blast alignment, and the results showed that the COI gene sequences had a high degree of similarity (99%) with X. flavipes records in the Genbank database. Therefore, we could determine that the insect was X. flavipes. In addition, the neighbor joining (NJ) was used to construct the evolutionary tree, and 1,000 repeated tests were conducted on the confidence levels of each branch. Based on the phylogenetic tree, we've found that X. flavipes belongs to Xylocoris genus. Based on morphology and COI sequence identification, we confidentiy determined that the collected natural enemy insect was X. flavipes. This is the first time that the identification of X. flavipes is being investigated from morphology and molecular biology. The research results are helpful to identify and distinguish the species of flower bugs, and beneficial for the better application of X. flavipes in biological control.

Attraction characteristics of insect pests and natural enemies according to the vertical position of yellow sticky traps in a strawberry farm with high-raised bed cultivation

Abstract The objectives of study was to evaluate the vertical space of flying insects using YST (yellow sticky traps) trapping in a strawberry farm with a high-raised bed system; with assuming the presence of species-specific flying zone. The experimental farm used styrofoam beds (width 30 cm, depth 20 cm) placed on a supporting frame 70 cm high. Small YSTs (12.5 × 7.5 cm, single sticky side) were installed vertically around the high-raised bed system in a 3 × 7 configuration (column × row) vertically at 30-cm intervals, reaching 270 cm high, and spaced 50 cm apart horizontally. The trap positions within the second-ranking (here referred to as ‘zone’) to attract thrips were 60 cm traps above the top of the bed center (TBC), 30 cm traps above the side of the bed (SOB), and 70 cm traps from the ground on the SOB. The attraction zone of whiteflies was the same as that of the thrips except of the 60 cm traps above the SOB. The zones for leafhoppers were formed in all 60 cm traps above the top of the bed (TOB), the 90 cm side traps above the TOB, and 30 cm traps above the TBC. Aphids were frequently attracted at all 90 cm traps above the TBC and 60 cm above the TBC. Sciarid pests were mostly attracted to the traps placed just below the bed center. The zones of natural enemies (total) were formed in 30 cm above the TBC and 70 cm from the ground at the SOB. Thus, the zone 60 cm above the TBC was common position where various pests were frequently attracted with reducing a harmful effect on natural enemies. Consequently, our results could be used as a guideline for the use of YSTs in strawberry farms with high-raised bed systems until new directions are developed.

Comparing the effects of GM and non‐GM soybean varieties on non‐target arthropods

AbstractIn order to guarantee the safety of genetically modified (GM) soybean crops, it is important to assess the potential toxicity of their expressed insecticidal proteins to non‐target organisms. In the present study, the effects of the GM soybean Insulin‐like Growth Factor (IGF), which is tolerant to the herbicide glufosinate, on plant‐dwelling non‐target insects and arachnids were evaluated in soybean agroecosystems. For comparison, the non‐GM parental cultivar of soybean Gwangan‐kong was used as a control. Data were collected in 2016 and 2017 via surveying at Ochang and Jeonju, Korea. In total, 13,031 individual insects and arachnids, representing 64 families in 11 orders, were captured during the study. Firstly, the results indicate that the GM soybean IGF did not negatively affect plant‐dwelling non‐target insects and arachnids. However, the numbers of captured individuals on both IGF and Gwangan‐kong were higher at Ochang in 2017. The occurrence of insect pests, natural enemies, and other insects differed significantly according to region, region and survey year, and survey year, respectively. In addition, the dominance, diversity, evenness, and richness indices for the collected insects varied significantly among the regions and survey years regardless of soybean variety. The score from PROXSCAL multidimensional scaling using combined data showed that insects and arachnids in different natural environments were separated by their cultivation regions and years irrespective of soybean cultivars.

Kelimpahan Dan Keragaman Serangga OPT (Organisme Pengganggu Tanaman) dan Musuh Alaminya pada Tanaman Jagung dan Padi dengan Sistem Rotasi Tanaman

Insects in agricultural ecosystem can play a role as pests or natural enemies. The abundance and diversity of insect pests and natural enemies are interconnected because insect pests are food for natural enemy insects. The aims of the study were to compare the abundance and diversity of pest insects and natural enemies of corn and rice plant, and to determine the similarity of pest insects and natural enemies of corn and rice plant using crop rotation systems. The sampling has performed four times i.e, in the vegetative phase of corn, generative corn, vegetative rice, and generative rice. The sampling method used sweep net method. The results showed that the number of individual pest insects and natural enemies of each growth phase of corn plants were lower than rice plants. The number of species pest insect and natural enemies of each growth phase of corn plants were lower than rice plants. In addition the diversity of pest insect of each growth phase of corn plants was higher than rice plants while the diversity of natural enemies in each growth phase of corn plants was lower than rice plants. The diversity index of pest insects and natural enemies of each growth phase in corn plants and rice plants was in the medium category. The presence of pest insects and natural enemies in each growth phase of corn and rice plants shows the species in the two compared ecosystems were different.

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.

Seasonal incidence and population dynamics of castor pests and their natural enemies in Tamil Nadu

Seasonal occurrence of insect pests and natural enemies on castor recorded consecutively for four years (2015-19 to 2018-19) showed that the sucking pests incidence was higher compared to defoliators and capsule borer. The peak incidence of leafhopper started from November to January in all the years with the peak population ranging from 24.8 to 84.5 leafhoppers/3 leaves/plant. Thrips population peaked during November and highest population of 432.8 thrips/spike was recorded during 2016-17. Whitefly population was recorded during December to January with peak population of 224.3/plant noticed in 2016-17. Defoliator population was recorded from October to November and the parasitisation of semilooper by Snellenius maculipennis was up to 66.6 per cent.