Field Pests Research Articles

Life history traits and rearing protocol of <i>Microvelia pulchella</i> (Hemiptera: Veliidae): a potential biological control agent and model for behavioral and ecological studies

Microvelia pulchella, a semiaquatic predatory bug widely distributed in the Neotropics, holds great potential as a biocontrol agent against disease-vector mosquitoes and pests in paddy rice fields. Moreover, insects belonging to the genus Microvelia have served as valuable model organisms for ecological and behavioural research. Considering this, our study aimed to establish an enhanced laboratory rearing protocol for M. pulchella based on existing methodologies. The protocol encompasses a decision-making flowchart to optimize the rearing process, a standardized method for accurately determining egg and nymph ages, and photographs illustrating all life stages and sexes of the insect. Additionally, we sought to characterize key life history traits of this species. Our detailed rearing procedure involves utilizing different containers tailored to each insect stage and specific requirements. We observed an average development time of 20.6 days from egg to adult at a temperature of 25°C (room temperature). Interestingly, male adults reared in the laboratory exhibited smaller sizes compared to their field-collected counterparts, while females displayed similar sizes across conditions. Female M. pulchella demonstrated an average egg production of 211.77 eggs, with the highest fecundity occurring within the first five weeks. Fertility followed a similar pattern, peaking during this period. In terms of longevity, females exhibited an average survival time of 74 days, whereas males lived for approximately 91 days. M. pulchella proves to be a convenient model organism for conducting non-invasive experiments, given the multitude of informative traits that can be measured. Additionally, the rearing procedure is cost-effective, straightforward, and requires minimal space.

Overexpression of Brassica napus COMT1 in Arabidopsis heightens UV-B-mediated resistance to Plutella xylostella herbivory.

UV-B radiation regulates numerous morphogenic, biochemical and physiological responses in plants, and can stimulate some responses typically associated with other abiotic and biotic stimuli, including invertebrate herbivory. Removal of UV-B from the growing environment of various plant species has been found to increase their susceptibility to consumption by invertebrate pests, however, to date, little research has been conducted to investigate the effects of UV-B on crop susceptibility to field pests. Here, we report findings from a multi-omic and genetic-based study investigating the mechanisms of UV-B-stimulated resistance of the crop, Brassica napus (oilseed rape), to herbivory from an economically important lepidopteran specialist of the Brassicaceae, Plutella xylostella (diamondback moth). The UV-B photoreceptor, UV RESISTANCE LOCUS 8 (UVR8), was not found to mediate resistance to this pest. RNA-Seq and untargeted metabolomics identified components of the sinapate/lignin biosynthetic pathway that were similarly regulated by UV-B and herbivory. Arabidopsis mutants in genes encoding two enzymes in the sinapate/lignin biosynthetic pathway, CAFFEATE O-METHYLTRANSFERASE 1 (COMT1) and ELICITOR-ACTIVATED GENE 3-2 (ELI3-2), retained UV-B-mediated resistance to P. xylostella herbivory. However, the overexpression of B. napus COMT1 in Arabidopsis further reduced plant susceptibility to P. xylostella herbivory in a UV-B-dependent manner. These findings demonstrate that overexpression of a component of the sinapate/lignin biosynthetic pathway in a member of the Brassicaceae can enhance UV-B-stimulated resistance to herbivory from P. xylostella.

Acute sublethal exposure to ethiprole impairs physiological and oxidative status in the Neotropical fish Astyanax altiparanae

Ethiprole, a phenylpyrazole insecticide, has been increasingly used in the Neotropical region to control stink bug pests in soybean and maize fields. However, such abrupt increases in use may have unintended effects on non-target organisms, including those inhabiting freshwater ecosystems. Here, we evaluated the effects of acute (96 h) sublethal exposure to ethiprole (up to 180 μg/L, which is equivalent to 0.013% of the recommended field dose) on biomarkers of stress in the gills, liver, and muscle of the Neotropical fish Astyanax altiparanae. We further recorded potential ethiprole-induced effects on the structural histology of A. altiparanae gills and liver. Our results showed that ethiprole exposure increased glucose and cortisol levels in a concentration-dependent manner. Ethiprole-exposed fish also exhibited higher levels of malondialdehyde and greater activity of antioxidant enzymes, such as glutathione-S-transferase and catalase, in both gills and liver. Furthermore, ethiprole exposure led to increased catalase activity and carbonylated protein levels in muscle. Morphometric and pathological analyses of the gills revealed that increasing ethiprole concentration resulted in hyperemia and loss of integrity of the secondary lamellae. Similarly, histopathological analysis of the liver demonstrated higher prevalence of necrosis and inflammatory infiltrates with increasing ethiprole concentration. Altogether, our findings demonstrated that sublethal exposure to ethiprole can trigger a stress response in non-target fish species, which may lead to potential ecological and economic imbalances in Neotropical freshwater systems.

Characterization and functional analysis of an α-adrenergic-like octopamine receptor in the small brown planthopper Laodelphax striatellus

As an important biogenic amine in invertebrates and corresponding to the neurotransmitter norepinephrine in vertebrates, octopamine (OA) regulates diverse physiological and behavioral processes by binding to specific octopamine receptors (OARs) in invertebrates. At present, OARs have been identified and characterized in several insects. However, less is known about the OARs of Laodelphax striatellus, one of the most destructive pests in East Asian rice fields. In the present study, an α1-adrenergic-like OAR (LsOA1) from L. striatellus was cloned. LsOA1 has the typical characteristics of G-protein coupled receptors and is clustered with other insect homologs. The transcript level of LsOA1 varied in various stages and tissues, and was highly expressed at the egg stage and in the brain. Silencing of LsOA1 causes a reduction in vitellogenin (LsVg) and vitellogenin receptor (LsVgR) expression. Although LsOA1 interference did not affect the fecundity and survival of L. striatellus, the hatching rate of L. striatellus was significantly reduced, and the hatching period was prolonged. The decrease in the amount of honeydew excreted after silencing LsOA1 indicates that LsOA1 may be involved in regulating the feeding behavior of L. striatellus. In addition, the interference of LsOA1 significantly reduced the expression of capsid protein (CP) and viral RNA3 segment (RNA3) in rice stripe virus (RSV)-viruliferous L. striatellus, but did not affect the vertical transmission rate of RSV. The present study demonstrated that LsOA1 played a crucial role in the physiological and behavioral processes of L. striatellus, which will provide the basis for developing a new target gene for pest control.

Farm2Fork through the lens of community ecology: concepts and applications in postharvest storage

The environment in which postharvest crops are processed and stored is a dynamic ecosystem influenced not only by environmental factors such as temperature and humidity, but also by biotic influences such as humans and insects. Abiotic influences such as variation in landscapes of warehouses, processing facilities, storage and shipping containers, and urban and agricultural settings can also drive changes in ecosystem processes for insects living in a postharvest system. Principles of community ecology can help to tease apart broad interactions among the environment including succession, interactions with conspecifics that lead to competition and niche partitioning, behavioral ecology variation, and physiology and developmental changes. Focusing on these concepts for integrated pest management (IPM) for stored product insect pests can help pest managers to better predict risk thresholds and develop targeted approaches for treatments. Typically, pest management decisions focus on single species without regards to the interactions with other species. Without consideration of the entire ecosystem, targeted treatments for one species can have both direct and indirect impacts on other species that may have equally detrimental effects on stored products. Current knowledge of stored product ecosystems lags behind what is known for field pest ecosystems, and hinders our ability to design effective control strategies for the whole system. Here, we present a review of work on stored product insect pests using a community ecology lens. We analyze how the current state of the knowledge regarding species interactions and variation and incorporating factors such as movement, species interactions, energy transfer models in succession, behavior, and effects of climate change in ecological modeling can be used to better develop and implement more effective postharvest IPM. Implementing these concepts will significantly improve management of these insects and can help reduce time and cost associated with managing and treating insect infestations.

Monitoring and characterization of field‐evolved resistance to diamide insecticides in Spodoptera litura collected from eastern China

AbstractSpodoptera litura is a notoriously destructive pest, which infests horticultural plants and economically important crops worldwide. Several generations of diamide insecticides have been used to combat S. litura throughout the world, causing various levels of resistance to this class of insecticides among wild S. litura populations. In this work, we monitored resistance to five diamide insecticides among 10 S. litura populations sampled from eastern China in 2022. In comparison with Lab‐S the susceptible strain, five of the tested populations displayed high susceptibility to three of the five diamide insecticides (cyantraniliprole, broflanilide and tetraniliprole). In contrast, there was significant resistance to the other two tested diamide insecticides, flubendiamide and chlorantraniliprole, in seven of the field‐collected populations. The Shanghai (SH) population showed high resistance to chlorantraniliprole (77.0‐fold), flubendiamide (25.5‐fold) and cyantraniliprole (27.8‐fold), respectively, than the strain of Lab‐S. Results of synergism tests in the SH population revealed that diethyl maleate (DEM) and piperonyl butoxide (PBO) greatly inhibited chlorantraniliprole resistance. The progeny of reciprocal crosses between the Lab‐S and SH populations presented dominance degrees of F1 progenies, suggesting that the chlorantraniliprole resistance was autosomal and incompletely recessive in SH. Above results of the current work offer useful knowledge for future formulation of field pest management strategies, allowing farmers to delay the development of resistance to diamide insecticides and thus promote sustainable management of S. litura.

Identification and characterization of Prx5 and Prx6 in Chilo suppressalis in response to environmental stress.

The antioxidant proteins, peroxiredoxins (Prxs), function to protect insects from reactive oxygen species-induced toxicity. In this study, two Prx genes, CsPrx5, and CsPrx6, were cloned and characterized from the paddy field pest, Chilo suppressalis, containing open reading frames of 570 and 672 bp encoding 189 and 223 amino acid polypeptides, respectively. Then, we investigated the influence of various stresses on their expression levels using quantitative real-time PCR (qRT-PCR). The results showed expression of CsPrx5 and CsPrx6 in all developmental stages, with eggs having the highest level. CsPrx5 and CsPrx6 showed higher expression in the epidermis and fat body, and CsPrx6 also showed higher expression in midgut, fat body, and epidermis. Increasing concentrations of insecticides (chlorantraniliprole and spinetoram) and hydrogen peroxide (H2 O2 ) increased the expression levels of CsPrx5 and CsPrx6. In addition, the expression levels of CsPrx5 and CsPrx6 were almost markedly upregulated in larvae under temperature stress or fed by vetiver. Thus, CsPrx5 and CsPrx6 upregulation might increase the C. suppressalis defense response by reducing the impact of environmental stress, providing a better understanding of the relationship between environmental stresses and insect defense systems.

Cyantraniliprole seed treatment effectively controls wireworms (Pleonomus canaliculatus Faldermann) and white grubs (Anomala corpulenta Motschulsky) in maize fields

Wireworms and white grubs are destructive underground pests in maize fields in China. Cyantraniliprole has good control effect on coleoptera pests. Here, we evaluated the toxicity of cyantraniliprole to the second instar larvae of Anomala corpulenta Motschulsky and third-instar of larvae of Pleonomus canaliculatus Faldermann and the effects of sublethal concentrations on the activity of antioxidant and detoxification enzymes. We also explored the efficacy of cyantraniliprole on underground pests under indoor and field conditions. The LC50 of cyantraniliprole for the third instar larvae of P. canaliculatus was 23.3712 mg/L, and that for the second instar larvae of A. corpulenta was 5.9715 mg/L. Cyantraniliprole can activate the activity of superoxide dismutase (SOD), peroxidase (POD), and glutathione S-transferase (GST) to different degrees at a sublethal dose. According to the pot experiment and the control efficacy test in the field, the indoor control effect of cyantraniliprole seed treatment on P. canaliculatus and white grubs was approximately 80%, and the maximum increase in yield achieved through cyantraniliprole application was approximately 15% in the field efficacy test. Cyantraniliprole has a strong control effect on wireworms and white grubs, so it can be used to treat seeds to control underground pests in maize fields.

Ovicidal potential of plant extract mixtures against the Asian spongy moth (Lymantria dispar asiatica)

The Asian spongy moth (ASM, Lymantria dispar asiatica) is a destructive pest of forests, agricultural fields, and urban areas. Plant extract mixtures were evaluated as alternative tools for integrated pest management targeting the overwintering eggs of ASM. When formulated with an adjuvant able to penetrate the hairy egg mass, plant extract mixtures inhibited egg hatching. The extract mixture (cinnamon extract 5% + citronella oil 10% + citrus oil 30% + derris extract 10% + neem extract 20% + penetrating surfactant 25%) with the highest ovicidal activity (97.6% mortality) is a potential botanical insecticide for use against ASM eggs. Susceptibility to mortality from plant extract mixtures increased with egg maturation. Optimal timing for control of overwintering ASM eggs corresponded to the period in spring when larvae inside eggs were fully differentiated. These results will help improve control efficacy with a day-degree model that predicts egg hatch as well as future development nano-formulations.

The influence of Ahy1 strain of Acremonium hansfodii on functional response of Neoseiulus barkeri to Tetranychus urticae

The two spotted spider mite (TSSM) Tetranychus urticae is one of the most economically key mite pests of fields and greenhouse crops over the world. In order to clarify the control efficacy of Neoseiulus barkeri on Tetranychus urticae in the presence of entomopathogenic fungus (EPF) Acremonium hansfodii. This study was conducted to evaluate the control of combining N. barkeri with A. hansfodii against T. urticae. The results showed that the functional response of N. barkeri treated with Ahy1 strain to T. urticae was Holling type II equation. Among these, the highest predation number and the shortest attack time were obtained for the predator feeding on eggs, then followed by feeding on nymphs, female adults ranked as the lowest. That of N. barkeri to T. urticae treated with Ahy1 strain was also Holling type II equation. The predation capacity of N. barkeri on nymphs and female adults of T. urticae treated by Ahy1 strain increased with the increase of the concentration of Ahy1 strain, but that when feeding eggs had no significant difference. Therefore, the combination of EPF with N. barkeri on control of TSSM had synergistic effects, which will provide the guidance to carry out combined utilization of entomogenous fungi with predatory mites.

ANALYSIS OF FARMERS' INCOME AFFECTED ATTACKS OF PLANT DISTURB ORGANISMS IN SUSOH DISTRICT SOUTHWEST ACEH DISTRICT

Paddy field in Susoh District, Southwest Aceh Regency are very vulnerable to the impacts of climate change such as drought and floods which have caused the intensity of attacks by Paddy field Pest Organisms (OPT) decreased as it had in the previous growing season. Some farmers make mitigation efforts by spraying pesticides according to the recommendations of the local Plant Pest Organism Observer (POPT), but some other farmers do not carry out mitigation due to considerations of production costs that are quite large and ultimately affect the total revenue and income of farmers. This study aims to look at the differences in total production and average income between farmers who mitigate and farmers who do not mitigate pest attacks. The sample was divided into two categories, each category was taken by 28 farmer respondents randomly. The results of the independent test sample t-test on production obtained t-count (4.056) greater than t-table () while for income obtained t-count (4.056) greater than t-table (2.46) indicating there is a difference in production and average income between mitigating and non-mitigating farmers. Total GKP production obtained by mitigating farmers was an average of 2.608 tons and farmers who did not mitigate an average of 2.011 tons. The average income of farmers who mitigate pest attacks is IDR 4,821,834.79 per 0.4 hectare or IDR 12,054,600 per hectare, while farmers who do not mitigate pest attacks are IDR 2,888,103.86 per 0.4 hectare or IDR 7,220,260 per hectare per planting season.

Nicotine-mediated dopamine regulates short neuropeptide F to inhibit brown planthopper feeding behavior in tobacco-rice rotation cropping.

The tobacco-rice rotation cropping (TRRC) is an ecologically friendly system that can both alleviate soil nicotine pollution and decrease the brown planthopper (BPH, Nilaparvata lugens Stål) fitness on rice. However, few studies on this green and effective rotational cropping system have been reported. In particular, the underlying mechanisms of TRRC on the significant reduction of field pest population at the molecular level is still unknown. Field investigation showed that BPH population decreased significantly in TRRC than in rice-rice successive cropping (RRSC) field. In addition, the short neuropeptide F (NlsNPF) and its receptor NlA7 of BPH had half-times lower levels in the TRRC field. Behavioral bioassay indicated a 1.93-fold increase in the number of salivary flanges of the dsNlsNPF group, while BPH fitness parameters, such as honeydew, weight gain, and mortality decreased significantly. Dopamine (DA) content in BPH decreased by ~11.1% under the influence of nicotine, and its presence increased the expression levels of NlsNPF and NlA7. Exogenous DA application eliminated the inhibitory effects of nicotine on BPH feeding and restored the fitness levels of its parameters. Independent application of either a mixture of dsNlsNPF with a nanocarrier or nicotine to the normal rice field revealed that the latter could produce better effects in combination with dsRNA. These findings confirmed that DA regulated NlsNPF to inhibit the BPH feeding behavior in TRRC. The results not only provided novel findings on the mechanism of pest-host interactions, but also presented new method for integrated pest management. © 2023 Society of Chemical Industry.

Population Dynamics and Estimation of Damage of the Spittlebug Aeneolamia varia on Sugarcane in Colombia by Using remote Sensing and Machine Learning Tools

The spittlebug (Aeneolamia varia) is one of the most important sugarcane pests in Colombia, where a recent increase in population and distribution specially in southwestern Colombia have led to the need for new technologies for integrated pest management. The objectives of this study were to determine the spatial distribution of this pest in commercial sugarcane fields and to validate machine learning (ML) tools for indirect injury detection and impact on yield (damage) using satellite images. This study was carried out in fields grown with the CC 01-1940 variety in El Cerrito, Valle del Cauca, Colombia, where systematic sampling of the populations (number of adults and nymphs per stem) was carried out. The spatial aggregation and distribution were determined using Moran’s index and point patterns, sequence observations, and analysis with distance indicators (Sadie). The indirect injury detection and quantification of the impact on production were carried out with a ML approach using satellite image products with 10 m spatial and five days temporal resolutions, obtained from a Sentinel-2 sensor using Google Earth Engine. The results indicated that spittlebug populations had an aggregate spatial behavior and high spatial dependence. In addition, the ML algorithms predicted spittlebug injury, and the effect on production was estimated at 26.4 tons of cane per hectare, which represented a 17% reduction in the expected yield. The use of spatial analysis and remote sensing tools are an alternative for indirect detection of injury and for understanding population dynamics of the pest in sugarcane, so they can become instrumental for decision-making on an integrated pest management program.

Pemanfaatan Tumbuhan Penghasil Pestisida Ramah Lingkungan Terhadap Mortalitas Hama Keong Mas (Pomacea canaliculata Lamarck) Pada Tanaman Padi Sawah

One of the main pests and many damaging rice plants is gold snails. The damage caused can reach 13.2–96.5%. This pest is difficult to control despite the application of pesticides. The purpose of the study was to determine the effect of organic pesticide-producing plants on the mortality of gold snail pests in rice fields. The experiment using Complete Randomized Design consisted of 5 treatments, namely: P0 (control), P1 (tubal root extract), P2 (soursop leaf extract), P3 (lemongrass extract), P4 (papaya leaf extract) and P5 (jatropha leaf extract). The results showed that the highest average consumption rate was found at P1 (70.73%) and the lowest at P0 (1.73%). The highest average mortality rate from this pest was found at P1 (80) and lowest at P0 (0) during the observation period 4 hours after application. While at 8-hour observations the average mortality was highest at P4 and P5 (60) and lowest at P0 (13) after application. The highest average death time velocity was observed at P1 (3) and lowest at P0 (0) in the observation period 4 hours after application, while the highest average death time speed 8 hours after application was found at P4 and P5 (5) and lowest at P0 (2).

In vivo and in silico comparison analyses of Cry toxin activities toward the sugarcane giant borer

The sugarcane giant borer, Telchin licus licus, is an insect pest that causes significant losses in sugarcane crops and in the sugar-alcohol sector. Chemical and manual control methods are not effective. As an alternative, in the current study, we have screened Bacillus thuringiensis (Bt) Cry toxins with high toxicity against this insect. Bioassays were conducted to determine the activity of four Cry toxins (Cry1A (a, b, and c) and Cry2Aa) against neonate T. licus licus larvae. Notably, the Cry1A family toxins had the lowest LC50 values, in which Cry1Ac presented 2.1-fold higher activity than Cry1Aa, 1.7-fold larger than Cry1Ab, and 9.7-fold larger than Cry2Aa toxins. In silico analyses were performed as a perspective to understand putative interactions between T. licus licus receptors and Cry1A toxins. The molecular dynamics and docking analyses for three putative aminopeptidase N (APN) receptors (TlAPN1, TlAPN3, and TlAPN4) revealed evidence for the amino acids that may be involved in the toxin-receptor interactions. Notably, the properties of Cry1Ac point to an interaction site that increases the toxin's affinity for the receptor and likely potentiate toxicity. The interacting amino acid residues predicted for Cry1Ac in this work are probably those shared by the other Cry1A toxins for the same region of APNs. Thus, the presented data extend the existing knowledge of the effects of Cry toxins on T. licus licus and should be considered in further development of transgenic sugarcane plants resistant to this major occurring insect pest in sugarcane fields.

Identification and characterization of ABC proteins in an important rice insect pest, Cnaphalocrocis medinalis unveil their response to Cry1C toxin

Rice leaffolder (Cnaphalocrocis medinalis) is an important insect pest in paddy fields. Due to their essential role in the physiology and insecticidal resistance, ATP-binding cassette (ABC) proteins were studied in many insects. In this study, we identified the ABC proteins in C. medinalis through genomic data and analyzed their molecular characteristics. A total of 37 sequences with nucleotide-binding domain (NBD) were identified as ABC proteins and belonged to eight families (ABCA-ABCH). Four structure styles of ABC proteins were found in C. medinalis, including full structure, half structure, single structure, and ABC2 structure. In addition to these structures, TMD-NBD-TMD, NBD-TMD-NBD, and NBD-TMD-NBD-NBD were found in C. medinalis ABC proteins. Docking studies suggested that in addition to the soluble ABC proteins, other ABC proteins including ABCC4, ABCH1, ABCG3, ABCB5, ABCG1, ABCC7, ABCB3, ABCA3, and ABCC5 binding with Cry1C had higher weighted scores. The upregulation of ABCB1 and downregulation of ABCB3, ABCC1, ABCC7, ABCG1, ABCG3, and ABCG6 were associated with the C. medinalis response to Cry1C toxin. Collectively, these results help elucidate the molecular characteristics of C. medinalis ABC proteins, pave the way for further functional studies of C. medinalis ABC proteins, including their interaction with Cry1C toxin, and provide potential insecticide targets.

Developmental toxicity of a pymetrozine photo-metabolite, 3-pyridinecarboxaldehyde, in zebrafish (Danio rerio) embryos: Abnormal cardiac development and occurrence of heart dysfunction via differential expression of heart formation-related genes

Pymetrozine (PYM) is worldwide used to control sucking insect pests in rice-cultivated fields and it is degraded into various metabolites including 3-pyridinecarboxaldehyde (3-PCA). These two pyridine compounds were used to determine their impacts on aquatic environments, particularly on the aquatic animal model zebrafish (Danio rerio). PYM did not show acute toxicities in terms of lethality, hatching rate, and phenotypic changes in zebrafish embryos in the tested ranges up to a concentration of 20 mg/L. 3-PCA exhibited acute toxicity with LC50 and EC50 values of 10.7 and 2.07 mg/L, respectively. 3-PCA treatment caused phenotypic changes including pericardial edema, yolk sac edema, hyperemia, and curved spine, at a concentration of 10 mg/L after 48 h of exposure. Abnormal cardiac development was observed in 3-PCA-treated zebrafish embryos at a concentration of 5 mg/L with reduced heart function. In a molecular analysis, cacna1c, encoding a voltage-dependent calcium channel, was significantly down-regulated in the 3-PCA-treated embryos, indicating synaptic and behavioral defects. Hyperemia and incomplete intersegmental vessels were observed in 3-PCA-treated embryos. Based on these results, it is necessary to generate scientific information on the acute and chronic toxicity of PYM and its metabolites with regular monitoring of their residues in aquatic environments.

Constraints Faced By the Small-Scale Farmers in the Production of Major Crops Sorghum and Maize in Awdal Region, Somaliland

The study aimed at exploring constraints faced by small-scale farmers in the production of major crops such as Sorghum and Maize; and find out their relationship with the selected characteristics of the farmers with the constraints they faced. The small-scale farmers of Baki, Dilla, Sabawanag, and Idhanks under the Borama and Baki districts were the respondents of the study. Data were collected by using a pre-tested structured interview schedule with a randomly selected sample of 92 farmers from a population of 1,250 farmers. Results indicated that among ten selected characters of the farmers, education, cosmopolites, training received, knowledge of climate change, and extension media contact showed a positive significant relationship with the constraints faced by the small-scale farmers in the production of major crops like sorghum and maize. On the other hand, farm size, land cultivation area, and annual income showed a negative significant relationship. The rest of the characteristics such as age and farming experience did not show any significant relationship with the constraints faced by the farmers. The results also showed that the highest proportion of the farmers (65.2 percent) faced medium constraints, while 22.8 percent and 12.0 percent of them faced low and high constraints, respectively. Among the 18 selected constraints, the highest constraints facing index (CFI) was found for ‘attack of diseases and pests in crop field’ which is 276 and the lowest was ‘lack of co-operation from family members with a score of 56. The study suggests that these constraints need to be solved to ensure food security and increase agricultural production in Awdal Region, Somaliland.

An efficient mobile model for insect image classification in the field pest management

Accurately recognizing insect pest in their larva phase is significant to take the early treatment on the infected crops, thus helping timely reduce the yield loss in agricultural products. The convolutional neural networks (CNNs)-based classification methods have become the most competitive methods to address many technical challenges related to image recognition in the field. Focusing on accurate and small models carried on mobile devices, this study proposed a novel pest classification method PCNet (Pest Classification Network) based on lightweight CNNs embedded attention mechanism. PCNet was designed with EfficientNet V2 as the backbone, and the coordinate attention mechanism (CA) was incorporated in this architecture to learn the inter-channel pest information and pest positional information of input images. Moreover, combining the feature maps output by mobile inverted bottleneck (MBConv) with the feature maps output by average pooling to develop the feature fusion module, which implements the feature fusion between shallow layers and deep layers to address the loss of insect pest features in the down-sampling procedures. In addition, a stochastic, pipeline-based data augmentation approach was adopted to randomly enhance data diversity and thus avoid model overfitting. The experimental results show that the PCNet model achieved recognition accuracy of 98.4 % on the self-built dataset consisting of 30 classes of larvae, which outperforms three classic CNN models (AlexNet, VGG16, and ResNet101), and four lightweight CNN models (ShuffleNet V2, MobileNet V3, EfficientNet V1 and V2). To further verify the robustness on different datasets, the proposed model was also tested on two other public datasets: IP102 and miniImageNet. The recognition accuracy of PCNet is 73.7 % on the IP102 dataset, outperforming other models and 94.0 % on miniImageNet dataset, which is only lower than that of ResNet101 and MobileNet V3. The number of PCNet parameters is 20.7 M, which is less than those of traditional classic CNN models. The satisfactory accuracy and small size of this model makes it suitable for real-time pest recognition in the field with resource constrained mobile devices. Our code will be available at https://github.com/pby521/PCNet/tree/master.

Earliness and Crop Morphological Traits Modulate Field Pest Infestation in Green Gram.

Breeding has significantly improved drought tolerance in green gram but marked yield losses continue due to damage by insect pests. Important pests of green gram are pod borers, Maruca vitrata (F.), aphids, Aphis gossypii Glover and whiteflies, Trialeurodes vaporariorum (Westwood). Management of these pests has partly been constrained by the limited understanding of crop traits that modulate their infestation. Field experiments were conducted in southeastern Kenya to evaluate a collection of old and new green gram varieties for tolerance to field pests, and to identify traits that confer resistance. The old varieties were KS20 and N26, both released in 1990s whereas the modern counterparts were Biashara, Karembo, and Ndengu-Tosha. Results showed significant differences among the varieties in maturity, leaf area, leaf hair density, leaf moisture content, and pod wall thickness. Earliness significantly reduced pest infestation, whereby KS20 matured early while N26 was late, and the new varieties were intermediate. On average, across the three environments, leaf area (R2 ≥ 0.32) and leaf moisture content (R2 ≥ 0.18) positively correlated with pest infestation while leaf hair density (R2 ≥ 0.30), and pod wall thickness (R2 ≥ 0.54) showed a negative association with pod borer and aphid counts. However, results did not reveal any particular traits that associated with the varieties, which implied that breeding of green gram in Kenya has not selected for tolerance to field pests. Nonetheless, green gram field pest management practices could select for varieties with early maturity, open plant canopy, pubescent leaves, and thicker pod walls.