Field Pests Research Articles

Regulation of conidiation, polarity growth, and pathogenicity by MrSte12 transcription factor in entomopathogenic fungus, Metarhizium rileyi

Metarhizium rileyi, a well-known filamentous biocontrol fungus, is the main pathogen of numerous field pests, especially noctuid pests. To explore the potential factors involved in the fungal pathogenicity, MrSte12, an important and conserved functional transcription factor in mitogen-activated protein kinase pathway was carried out by functional analysis. Homologous recombination was used to disrupt the MrSte12 gene in M. rileyi. The deletant fungal strain exhibited malformed hyphae and impaired conidiogenesis, and conidia could not be collected from △MrSte12 in vitro towards SMAY medium. Although conidia could be collected again supplemented with KCl within SMAY medium, the conidial germination, growth and stress tolerance were much weaker compared with that in WT. Additionally, △MrSte12 showed a dramatic reduction in virulence in intra-hemolymph injections and no pathogenicity in topical inoculations against noctuid pests, which is due to the failure of appressorium formation. Moreover, the content of chitin and β-1, 3-glucan in cell wall significantly reduced in mutant conidia. These results indicate that the MrSte12 gene markedly contributes to invasive growth and conidiation, as well as the major pathogenicity in M. rileyi.

IN1167--Minor] Rice Water Weevil (Coleoptera: Curculionidae) Distribution and Management in Florida

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most widely distributed and destructive pest of rice, Oryza sativa L., in the United States (Way 1990). The following report provides a description of the rice water weevil, its distribution in the state of Florida, methodology for scouting, and options for managing this pest in commercial rice fields. The rice water weevil belongs to the family Curculionidae and feeds on a wide variety of plants belonging to the families Poaceae and Cyperaceae (Tindall and Stout 2003, Lupi et al. 2009). The rice water weevil is native to the southeastern United States and has been reported from all rice producing states in the United States (Whitehouse et al. 2019). Registered seed and foliar treatments can be applied as preventative control for anticipated economic damage by future weevil populations. Application of this permanent flood is the most important external influence on the interaction between the rice water weevil and rice (Stout et al. 2002).

Ecological Benefit Evaluation of Agricultural Heritage System Conservation—A Case Study of the Qingtian Rice-Fish Culture System

In order to better understand the developmental conditions and trends of the biodiversity at agricultural heritage sites, the structure and function of the ecosystem and ecological environment in Qingtian Rice-Fish Culture System is examined in the decade since the implementation of the GIAHS project. Through the collection of historical data and sample-plot survey, this study collates the data from 2005 to 2013 related to the heritage site to evaluate the ecological benefit of the Agricultural Heritage System conservation. The results show that: (1) Since the implementation of heritage conservation, the variety of traditional rice grown at the heritage sites basically remains stable, the varieties of other crops basically remain unchanged and the varieties of fruit trees and medicinal plants have developed at faster rates. As the ecological environment at the heritage sites gradually improved, the species and richness of the biodiversity in the ecosystem have increased, especially the increasing growth of egrets and boars. (2) From 2005 to 2013 in the Fangshan Town of Qingtian County, the ecosystem areas identified as river, forest, urban and bare land have increased. The increased area of the urban ecosystem is the largest one of them, which is up to 20.30 ha; while the area of the forest ecosystem has increased to 7.29 ha. The areas of wetland, reservoir, farmland and grassland have been reduced, and the area of grassland ecosystem has been reduced the most with a reduction of 28.87 ha. From the changes in the values of the ecosystem services of different ecosystem types, the values of forest ecosystem services have achieved the most growth, reaching up to 92000 yuan yr-1 and the growth of the river and bare land ecosystem service values are not obvious. (3) Over nearly a decade, the soil nutrients and the water quality of rice fields at the heritage site have not obviously changed and the plant diseases and insect pests in the rice fields have not been aggravated. The monitoring indexes are far better than the standard values. With the great support of the local government, the production and living conditions and the living environments of farmers in the villages of the heritage sites have been greatly improved through road reconstruction, water improvement, toilet enhancements and the greening, brightness and beautification of the villages.

Insect pest in rice field with legumes embankment applied by Beauveria bassiana vuill

The objectives of research is to determine the diversity of insect pests in rice fields and the effect of B. bassiana spraying around the ecosystem. The collection and observation of pest populations in rice and legumes embankments was held in Mappadaelo village, Tanasitolo District, Wajo Regency, South Sulawesi. Experiments used Mekongga rice varieties in four different fields with a distance between rice fields of around 200 - 300 m. Legumes in the embankment was planted a week after planting rice, the types of legumes: green beans, long beans and cowpeas. The research used Randomized Block Design eight treatment and four replication. Observation of pest insect of rice started from 14 days after planting used ten sample of legume plant in embankment (five samples legumes without B. bassiana spraying and five samples of plants sprayed B. bassiana). The insects were collected on the embankment used D-Vac, then the sample put in a bottle contain alcohol 70%. The interval collected sample used D-Vac was seven days. The results was showed the diversity of insect pests in rice field without spraying B. bassiana was 2.48 with the highest diversity index in treatment P1 of 0.71. The lowest insect diversity index on plants in rice field without B. bassiana spray as P3 treatment of 0.65. The diversity of pest insect in rice fields sprayed with B. bassiana was 2.28. The highest diversity index was found in treatment P7 of 0.75. The lowest insect diversity index in rice fields sprayed with B. bassiana was treatment P6 of 0.45. The conclusion of the study spraying the entomopathogenic fungi B. bassiana affected the diversity index of pest insect attacked rice plant.

Transcriptomics identifies key defense mechanisms in rice resistant to both leaf-feeding and phloem feeding herbivores

BackgroundOutbreaks of insect pests in paddy fields cause heavy losses in global rice yield annually, a threat projected to be aggravated by ongoing climate warming. Although significant progress has been made in the screening and cloning of insect resistance genes in rice germplasm and their introgression into modern cultivars, improved rice resistance is only effective against either chewing or phloem-feeding insects.ResultsIn this study, the results from standard and modified seedbox screening, settlement preference and honeydew excretion tests consistently showed that Qingliu, a previously known leaffolder-resistant rice variety, is also moderately resistant to brown planthopper (BPH). High-throughput RNA sequencing showed a higher number of differentially expressed genes (DEGs) at the infestation site, with 2720 DEGs in leaves vs 181 DEGs in sheaths for leaffolder herbivory and 450 DEGs in sheaths vs 212 DEGs in leaves for BPH infestation. The leaf-specific transcriptome revealed that Qingliu responds to leaffolder feeding by activating jasmonic acid biosynthesis genes and genes regulating the shikimate and phenylpropanoid pathways that are essential for the biosynthesis of salicylic acid, melatonin, flavonoids and lignin defensive compounds. The sheath-specific transcriptome revealed that Qingliu responds to BPH infestation by inducing salicylic acid-responsive genes and those controlling cellular signaling cascades. Taken together these genes could play a role in triggering defense mechanisms such as cell wall modifications and cuticular wax formation.ConclusionsThis study highlighted the key defensive responses of a rarely observed rice variety Qingliu that has resistance to attacks by two different feeding guilds of herbivores. The leaffolders are leaf-feeder while the BPHs are phloem feeders, consequently Qingliu is considered to have dual resistance. Although the defense responses of Qingliu to both insect pest types appear largely dissimilar, the phenylpropanoid pathway (or more specifically phenylalanine ammonia-lyase genes) could be a convergent upstream pathway. However, this possibility requires further studies. This information is valuable for breeding programs aiming to generate broad spectrum insect resistance in rice cultivars.

Biological Control of Insect Pests by Bacterial Species Present in the Environment: المكافحة الحيوية للآفات الحشرية بفعل أنواع بكتيرية متواجدة في البيئة

Because of the severe damage caused by insect pests in agricultural fields, which cost billions of dollars annually, countries used chemical pesticides to eliminate these pests. The continuous use of chemical pesticides led to many environmental impacts, besides the emergence of resistance to insect pests. Therefore, it was necessary to search for an effective treatment for insect pest problems that was environmentally friendly and safe for human health. Biological control of insect pests has gained considerable importance in agricultural fields for its efficiency and safety for humans and other non- target organisms. In addition to its natural presence in the environment, cheaper cost, and more environmentally friendly, And a better alternative to synthetic chemical pesticides as well as being environmentally safe, they not only help establish food security by fighting against insect pests but also ensure food safety, they have enormous potential for achieving agricultural sustainability and environmental safety. In this review, we will highlight the definition and classification of insect pests, microbial pesticides. Besides, the advantages and disadvantages of these kinds of pesticides. We will also focus on the most effective bacterial species used in the production of pesticides and protein toxins that kill insect pests, their mechanism of action, method of marketing, and application to insect pests. We have looked at future research in eradicating insect pests.

Entomopathogenic Fungi on Fabae bean Aphid, Aphis craccivora (Koch) (Hemiptera: Aphididae)

The Aphids, Aphis craccivora (Koch) is a serious pest in agricultural fields in Egypt. Entomopathogenic fungi are biological control agents of insects. The study was carried out on the aphid by using of Bio Catch, Verticillium lecanii, Bio Power, Beauveria bassiana and Bio Magic, Metarhizium anisopliae on A. craccivora. Laboratory experiments were done to measure the pathogenicity of three commercial compounds from entomopathogenic fungi, Bio Catch, V. lecanii, Bio Power, B. bassiana, and Bio Magic, M. anisopliae against adults and nymphs of A. craccivora. Three concentrations were used from all compounds, 107 , 108 and 109 spores/ml. at 22 ± 2°C and 75 ± 5 R.H. The concentration (109 spores/ml.) gave 100% mortality with V. lecanii and B. bassiana then M. anisopliae. The Lowest LC50 value of 2.1 x 106 spores/ml. was recorded by V. lecanii, which showed higher virulence compared to other entomopathogenic fungi. The LC50 values of V. lecanii, B. bassiana and M. anisopliae were 2.1 x 106 , 4.3 x 106 and 6.4 x 107 spores ml., respectively. At the highest concentration of 109 spores/ml., the Median LT50 values for V. lecanii, B. bassiana and M. anisopliae were 4.2, 5.2 and 7.0 days, respectively.

Potential ofFicus caricaextracts againstEuschistus heros: Toxicity of major active compounds and selectivity against beneficial insects

Using plant-based extracts and their constituents has been suggested as an alternative tool to replace or integrate with the synthetic compounds used to manage insect pests. Here, we evaluated the potential of extracts obtained from Ficus carica Linn (Moraceae) branches and leaves against the Neotropical brown stink bug, Euschistus heros, one of the most prevalent insect pests in soybean fields. We further isolated and evaluated the toxicity of the extracts' major components against E. heros. Additionally, by using computational docking analysis and toxicological approaches, we assessed the physiological basis for the selectivity of these extracts against beneficial insects such as pollinator bees (i.e. Apis mellifera and the Neotropical stingless bee Partamona helleri), ladybeetles (Eriopis connexa and Coleomegilla maculata), and lacewings (Chrysoperla externa). Our results demonstrate that branch (LC50 =5.9 [4.7-7.1] mg mL-1 ) and leaf (LC50 =14.1 [12.5-15.4] mg mL-1 ) extracts exhibited similar toxicity against E. heros. Our phytochemical analysis revealed psoralen and bergapten furanocoumarins as the major components of the extract. Based on our computational predictions, these molecules' differential abilities to physically interact with the acetylcholinesterases of E. heros and beneficial insects play relevant roles in their selectivity actions. The estimated LC90 values of branch (30.0mg mL-1 ) and leaf (30.0mg mL-1 ) extracts killed less than 12% of the beneficial insects. Overall, our findings revealed that furanocoumarin-rich extracts obtained from F. carica extracts have the potential to be used as alternative tools in the integrated management of stink bug pests. © 2021 Society of Chemical Industry.

Different Performance of Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae) among Four Potato Tuber Varieties under Laboratory Condition.

Simple SummaryPhthorimaea operculella is considered one of the most damaging potato pests in both field and storage. Learning the developmental performance of P. operculella on different potato varieties is necessary before developing management practices.The potato tuber moth Phthorimaea operculella Zeller is one of the most damaging potato pests in the world and is difficult to control as the larvae feed only inside potatoes. Evaluating the effects of performance of P. operculella on different potato varieties may help to facilitate the development of effective pest management practices. In our study, P. operculella reared on potato variety Lishu6 showed strong performance and on Qingshu 9 exhibited the poorest performance, while P. operculella fed on Hezuo 88 and Yunshu 304 performed moderately. Firstly, larval performance of P. operculella fed on Lishu 6 with that on Hezuo 88, Yunshu 304, and Qingshu 9 was compared by using an age-stage two-sex life table. Compared with larvae fed on Lishu 6, those fed on Qingshu 9 exhibited significantly lower survival, with only 5.56% developing to the adult stage. Secondly, the pupal weight experiment showed that the pupae weight of P. operculella feeding on Lishu 6 tubers (0.0123 g) was significantly heavier than that those feeding on Qingshu 9 (0.0102 g) (p < 0.001). Thirdly, female oviposition and larvae feeding preference indicated that females oviposited on Lishu 6 in preference to Qingshu 9 (p < 0.05, p < 0.001). Overall, this study demonstrated that Qingshu 9 is the least suitable host, and planting this variety over a large scale can provide a basis for the next step of P. operculella control.

A Comparative Analyses of the Complete Mitochondrial Genomes of Fungal Endosymbionts in Sogatella furcifera, White-Backed Planthoppers.

Sogatella furcifera Horvath, commonly known as the white-backed planthoppers (WBPH), is an important pest in East Asian rice fields. Fungal endosymbiosis is widespread among planthoppers in the infraorder Fulgoromorpha and suborder Auchenorrhyncha. We successfully obtained complete mitogenome of five WBPH fungal endosymbionts, belonging to the Ophiocordycipitaceae family, from next-generation sequencing (NGS) reads obtained from S. furcifera samples. These five mitogenomes range in length from 55,390 bp to 55,406 bp, which is shorter than the mitogenome of the fungal endosymbiont found in Ricania speculum, black planthoppers. Twenty-eight protein-coding genes (PCGs), 12 tRNAs, and 2 rRNAs were found in the mitogenomes. Two single-nucleotide polymorphisms, two insertions, and three deletions were identified among the five mitogenomes, which were fewer in number than those of four species of Ophiocordycipitaceae, Ophiocordyceps sinensis, Hirsutella thompsonii, Hirsutella rhossiliensis, and Tolypocladium inflatum. Noticeably short lengths (up to 18 bp) of simple sequence repeats were identified in the five WBPH fungal endosymbiont mitogenomes. Phylogenetic analysis based on conserved PCGs across 25 Ophiocordycipitaceae mitogenomes revealed that the five mitogenomes were clustered with that of R. speculum, forming an independent clade. In addition to providing the full mitogenome sequences, obtaining complete mitogenomes of WBPH endosymbionts can provide insights into their phylogenetic positions without needing to isolate the mtDNA from the host. This advantage is of value to future studies involving fungal endosymbiont mitogenomes.

Eleocharis dulcis (Burm.f) as a promising trap plant for the biocontrol of rice white stem borer, Scirpophaga innotata (Walker)

The rice white stem borer, Scirpophaga innotata Walker (Family: Crambidae) is a major lepidopteran pest of rice from seedling to ear setting stage. Due to their hidden life style, no satisfactory means of control other than systemic pesticide application, habitat management, and egg parasitism have been prescribed yet. It is observed that S. innotata use a plant, the Chinese water chestnut (Eleocharis dulcis (Burm. F.)) (Family: Cyperaceae) for oviposition. We investigated why and how S. innotata is benefited by using E. dulcis for oviposition to prescribe it as a trap plant for managing the pest. We surveyed moths and egg clutches, and studied functional traits of eggs, egg hatching, and egg parasitism in eggs deposited on rice and the chestnut for three years in Kaipad rice fields of peninsular India. We observed 20 times more egg clutches on the chestnut than on rice. The egg density in clutches and hatching rate were high in eggs deposited on the chestnut. Egg parasitism was meager and restricted only to the eggs deposited on rice. However, no larvae hatched on the chestnut in the lab survived. The results suggest that E. dulcis could be a dead-end trap plant for biological control of S. innotata. We do not rule out the probability of the moth using E. dulcis for oviposition, escaping from egg parasitoids, and most importantly for rapid spread of neonates to rice. We recommend using E. dulcis as a trap plant to trap the eggs and removing them to manage this pest in rice fields.

The overexpression of insect endogenous microRNA in transgenic rice inhibits the pupation of Chilo suppressalis and Cnaphalocrocis medinalis.

Chilo suppressalis and Cnaphalocrocis medinalis are destructive rice pests co-occurring in major rice-growing areas in China. RNA interference (RNAi)-based insect-resistant genetically engineered (IRGE) crops provide a promising approach for pest management by suppressing gene expression or translation. A microRNA (miRNA)-mediated IRGE rice line expressing endogenous Chilo suppressalis miRNA Csu-novel-260, showing significant resistance against Chilo suppressalis, provides an attractive control strategy for Chilo suppressalis by suppressing the expression of the disembodied (dib) gene expression. However, whether this transgenic line also shows the resistance against Cnaphalocrocis medinalis remains unknown. A spatiotemporal expression analysis of Csu-novel-260 in the transgenic rice line was performed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) to determine the paddy field pest exposure dose. In diet feeding assays, a chemically synthesized Csu-novel-260 agomir at 200 fmol g-1 significantly inhibited Chilo suppressalis pupation. However, larval development, survival and pupal weight were not significantly affected. Additionally, the transgenic line significantly affected Cnaphalocrocis medinalis pupation but not larval survival. The qRT-PCR showed that Csdib and Cmdib expression levels were significantly suppressed when the two pests fed on the transgenic line. Additionally, the transgenic line significantly decreased Cry1C-resistant and Cry1C-susceptible Chilo suppressalis larval survival in detached rice tissue feeding assays, indicating that Cry1C-resistant Chilo suppressalis was not cross-resistant to Csu-novel-260 expressed in miRNA-mediated IRGE rice. Our study demonstrated that miRNA-mediated IRGE rice significantly inhibited Chilo suppressalis and Cnaphalocrocis medinalis pupation. The results provide a new viewpoint for the application of RNAi-based plants and the inspiration for environmental risk assessment.

Susceptibility of the Egyptian Cotton Leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) to Entomocidal Crystal Proteins Cry1Ac and Cry 2Ab Baseline Responses

The present study maybe is the first attempt in Egypt to evaluate the effect of Entomocidal proteins (Cry toxins) from Bacillus thuringiensis (Bt)Cry 1Ac and Cry 2Ab againstthe Egyptian cotton leafworm Spodoptera littoralis. The cotton leafworm one of the important Lepidopteran species is the most important pests in cotton fields. It can be controlled using Genetically Modified (GM) crops expressing insecticidal Bt proteins like Bt cotton and Bt corn. The long-term success of this technology demands pest resistance management. Important information for the successful management of resistance is the baseline susceptibility of the different target pests to the different Bt proteins. The data on baseline susceptibility should enable risk assessors and managers to assess whether GM cotton produces a Bt protein in a high-dose to specific target organisms and resistance has evolved during the commercial cultivation of this GM cotton event. During this study, the toxicity of Cry 1Ac and Cry 2Ab from the bacterium Bacillus thuringiensis to larvae of S. littoralis was assessed using first instar larvae with diet incorporation bioassays. Larvae reared (4 generations) from 2 populations of S. littoralis collected from major cotton-growing regions of Sohag and Assuit Governorates were tested. The LC50 for the Assuit strain was 140.11 and 88.54 µg/ml forCry 1Ac and Cry 2Ab, respectively. While, the LC50 for the Sohag strain was 410.75 and 37.62 µg/ml for Cry 1Ac and Cry 2Ab, respectively. On the other hand, the laboratory strain was more sensitive for the same Cry’s (Cry 1Ac and Cry 2Ab) the LC50 was13.40 and 0.23 µg/ml, respectively. The lethal concentration (LC50) against S. littoralis for 2nd and 4th instars larvae when using the B. thuringiensis as spores (commercial product) was 1.16 and 2.49 for 2nd and 4th instars, respectively. This study is very important as a preliminary step and baseline ahead of the commercial cultivation and production of Genetically Modified cotton (Bt cotton).

Comparison of Invasive Apple Snail (Pomacea canaliculata) Behaviors in Different Water Temperature Gradients

Pomacea canaliculata (known as invasive apple snail) is a freshwater snail native to South America that was introduced into many countries (including Asia and North America) as a food source or for organic farming systems. However, it has invaded freshwater ecosystems and become a serious agricultural pest in paddy fields. Water temperature is an important factor determining behavior and successful establishment in new areas. We examined the behavioral responses of P. canaliculata with water temperature changes from 25 °C to 30 °C, 20 °C, and 15 °C by quantifying changes in nine behaviors. At the acclimated temperature (25 °C), the mobility of P. canaliculata was low during the day, but high at night. Clinging behavior increased as the water temperature decreased from 25 °C to 20 °C or 15 °C. Conversely, ventilation and food consumption increased when the water temperature increased from 25 °C to 30 °C. A self-organizing map (an unsupervised artificial neural network) was used to classify the behavioral patterns into seven clusters at different water temperatures. These results suggest that the activity levels or certain behaviors of P. canaliculata vary with the water temperature conditions. Understanding the thermal biology of P. canaliculata may be crucial for managing this invasive snail.

Identification, behavior analysis, and control of snail pest in agricultural fields using signal analysis and nanoparticles

Giant African snail has been considered as the most challenging and evolving pest all over the world. This Pest is recognized as one of the topmost 100 destructive species in the world. This Snail is an agricultural pest devours only vegetables, fruits and sometimes sand. It also disturbs the households. It has the capacity to transmit both human and plant pathogens. This snail feeds on the stem, leaves, and flower of the cauliflower. This paper gives the brief study of various behavior of Giant African snail in acoustic environment. The Signals of various behavior of snails are recorded and analyzed using a MATLAB 2019 software. The time domain specification and frequency domain specification of pest Snails are done. Eradication of snail from its habitat is the tedious process. The eradication of snail is quite simple when it is detected automatically. This paper also suggests the identification of snails automatically by its acoustic signals and uses Machine Learning algorithm for effective detection. Added to above, the addition of the 5% of AgNP nanoparticles eliminated the presence of Giant African snail in the agricultural fields.

Design and development of a robot for spraying fertilizers and pesticides for agriculture

The agriculture industry is one that is highly resource- and labour-intensive. As such, farmers are increasingly turning to technology and automation to address this issue. However, agricultural robots are far too complicated, slow, and costly to be made publicly available. As a result, the agriculture sector still lags behind in integrating modern technologies. This research paper details the development of a low-cost agricultural robot for spraying fertilizers and pesticides in agriculture fields as well as for general crop monitoring. The prototype system is a two-wheeled robot that consists of a mobile base, a spraying mechanism, a wireless controller for controlling the robot movement, and a camera for crop health and growth monitoring as well as detecting the presence of pests in the agriculture field. Tests conducted on the prototype system show that while the productivity of the robot in terms of crop coverage is slightly lower than a human worker, the labour cost savings afforded by the agricultural robot prototype is much greater as it functions completely in an autonomous mode and only requires the operator to control the robot when placing it at the start of the crop path. Furthermore, the prototype system also provides greater resource savings and reduction in the contamination of underground water sources due to leeching process, thus achieving precision agriculture goals. Lastly, the excellent battery life of the prototype system ensures that there will be no increase in the operation times and reduction in the efficiency of the fertilizer and pesticide spraying process due to the recharging times when replacing human workers. Future recommendations include making the agricultural robot fully autonomous, using either a rail- or line-following system, to further reduce the labour requirements and costs.

Diversity, relative abundance and temporal spread of insects associated with Roselle (Hibiscus sabdariffa L.) at Makurdi, Nigeria

Roselle, Hibiscus sabdariffa L., is cultivated extensively for food and income generation in Africa, but research on biotic constraints to its production has been scanty. A 48-plot (5m×5m wide each) field experiment laid in randomized complete block design was used to document the relative abundance (% RA), diversity, richness, and temporal spread of insect species infesting the crop at Makurdi, Nigeria. The insects were collected from all parts of early- and late-sown green-calyx (H. sabdariffa var. sabdariffa) and red-calyx (H. sabdariffa var. altissima) Roselle shoots. About 101 species (81 herbivores, 18 predators, 1 parasitoid, and 1 pollinator) in 45 families and 8 orders were collected. Shannon’s diversity index (2.1-2.4) and Margalef’s richness index (8.3-10.0) indicate a rich diversity of species on the crop. However, evenness of species, measured by Buzas and Gibson’s index, was low (0.1-0.41). The orders Coleoptera and Hemiptera accounted for 72.0% of the collection. Nineteen species were moderately (≥1 RA&lt;5%) to highly abundant (RA≥10%) on the crop and among them Monolepta thompsoni Allard and Nisotra sjostedti Jac. were ubiquitous causing extensive leaf perforation all through the entire crop growth period. At the reproductive stage of growth, Dysdercus volkeri Fab., Oxycarenus hyalinipennis Costa and Earias sp. were the dominant insects causing fruit and seed damage. The frequency of occurrence and densities of M. thompsoni Allard, N. sjostedti Jac., D. volkeri Fab., O. hyalinipennis Costa and Earias sp. as well as their extensive damage, indicate that they are the key field pests of Roselle at Makurdi.

Pest control using farming awareness: Impact of time delays and optimal use of biopesticides

We investigate a mathematical model in crop pest management, considering plant biomass, pest, and the effect of farming awareness. The pest population is divided into two compartments: susceptible pest and infected pest. We assume that the growth rate of self-aware people is proportional to the density of healthy pests present in the crop field. Impacts of awareness is modeled via a saturated term. It is further assumed that self-aware people will adopt biological control methods, namely integrated pest management. Susceptible pests are detrimental to crops and, moreover, there may be some time delay in measuring the healthy pests in the crop field. A time delay may also take place while becoming aware of the control strategies or taking necessary steps to control the pest attack. In agreement, we develop our model incorporating two time delays into the system. The existence and the stability criteria of the equilibria are obtained in terms of the basic reproduction number and time delays. Stability switches occur through Hopf-bifurcation when time delays cross critical values. Optimal control theory has been applied for the cost-effectiveness of the delayed system. Numerical simulations illustrate the obtained analytical results.

Toxicity, residue and risk assessment of tetraniliprole in soil-earthworm microcosms

Maize seed treatment with chemicals to control underground pests is a common agricultural practice, but inappropriate use of insecticides poses a considerable threat to plant development and soil nontarget organisms. In this study, the availability of tetraniliprole seed dressing to control the black cutworm Agrotis ipsilon (Lepidoptera: Noctuidae) in the maize seeding stage and its safety to earthworms (Eisenia fetida) were investigated. The selective toxicity (ST) of tetraniliprole between E. fetida and A. ipsilon was greater than 4000. No significant adverse effect of tetraniliprole seed treatment on the germination of maize seeds was observed at concentrations of 2.4–9.6 g a.i. /kg seed. Compared with the untreated control, seed treatment with tetraniliprole at 9.6 g a.i. /kg seed greatly reduced the percentage of damaged plants from 88.73% to 26.67%, and achieved the highest control effect of 69.91%. Tetraniliprole of 2.4 g a.i. /kg seed can effectively inhibit A. ipsilon until 14 days after seed germination, with the lowest mortality rate of 44.44%. During the entire exposure period, the maximum residual concentration of tetraniliprole detected in the soil (5.86 mg/kg) was considerably lower than the LC50 value of tetraniliprole to E. fetida (>4000 mg/kg). According to the low-tier risk assessment, the highest risk quotient (RQ) of tetraniliprole seed treatment to earthworms at test concentrations was 2.8 × 10−3, which was evaluated as acceptable. This study provided data support for tetraniliprole seed treatment to control underground pests in maize fields.

Identification of a novel trait associated with phytotoxicity of an insecticide etofenprox in soybean.

Synthetic insecticides are widely used to control pests in various crop fields. Especially in soybean [Glycine max (L.) Merr.] fields, the insecticide etofenprox, which is a pyrethroid derivative, has been used to manage hemiptera pests. To date, soybean phytotoxicity response has not been reported to etofenprox derivatives, two Korean cultivars, Danbaek and Kwangan, were first identified to show leaf shape shrinkage damage after etofenprox application. We confirmed that the causal substance for phytotoxicity is etofenprox and that it had dosage effects. Through genetic analysis using three F2 populations, sensitivity to etofenprox is confirmed to be managed by a single dominant gene, and that gene is the same in Danbaek and Kwangan. Although further genetic research is required to identify the gene responsible for sensitivity to etofenprox, the results of this study will help to elucidate the interaction between plants and chemicals when breeding new cultivars or developing pesticides.