Journal of Plant Diseases and Protection最新文献

Meloidogyne hispanica infects many economically important crops worldwide and has been listed as a quarantine pest in many countries and as an invasive alien species in China. Accurate identification of this pathogen is essential for the establishment of efficient and sustainable integrated pest management programs. During the field investigations in Hainan, China, we discovered galled roots caused by nematode infestation in the pepper field. Further identification of the nematode isolated from the root galls, including morphological and molecular techniques, confirmed that the isolated population infesting the pepper roots belonged to the species M. hispanica. Upon artificial inoculation under greenhouse conditions, the isolated nematodes induced symptoms that closely resembled those observed in the field. To the best of our knowledge, this is the first documented case of M. hispanica parasitizing pepper crops in China, which will provide valuable basis to formulate targeted control strategies.

In response to the pressing agricultural concern posed by insect pests, leading to substantial crop losses and compounded by the challenges of distinguishing between similar species, this study presents an innovative solution using convolutional neural networks (CNNs) for rapid and accurate insect species recognition, addressing the agricultural challenge of insect pests and species differentiation. Initially, six pre-trained CNN base models (VGG16, VGG19, ResNet50, Inception-V3, Xception, and MobileNet) are fine-tuned and perform classification on our unique dataset from Kerala, India, called KSDAgriPest dataset with 33 insect classes. Later, four best-performing base models, VGG16, Inception-V3, Xception, and MobileNet, were modified and retrained using appropriate transfer learning and fine-tuning strategies and are ensembled via all possible combinations of three base models using genetic algorithm (GA) optimized weighted voting, is called GAEnsemble and the generated models are called Ensemble Variants (EV). In the final stage, two top-performing EVs are ensembled. The proposed “Genetic Algorithm-based Ensemble of Ensemble” (GA2Ensemble) achieves an impressive 99.34% accuracy on the KSDAgriPest dataset and competitive results on other datasets (DO: 98.99%, SMALL: 96.21%, IP102: 69.56%). GA2Ensemble proves effective for insect pest species identification, particularly on challenging datasets.

The corn stunt disease is a major threat to maize production in Brazil. In addition to the more common insect vector Dalbulus maidis (Hemiptera: Cicadellidae), the African species Leptodelphax maculigera (Hemiptera: Delphacidae) was recently found in the Brazilian states of Goiás, Paraná and Santa Catarina, raising concern regarding its potential ability to transmit stunt pathogens. We confirmed the presence of L. maculigera in the state of Rio Grande do Sul by conducting a population survey with yellow sticky traps and light traps in three different sites, although it corresponded to only 2.3% of the D. maidis population captured during the same period. Molecular analysis via RT-qPCR multiplex confirmed the simultaneous infection of L. maculigera by two corn stunt pathogens—Maize rayado fino virus (MRFV) and Maize bushy stunt phytoplasma (MBSP)—in 76.9% of the samples, while the remaining 23.1% showed single infection by MRFV. The confirmation of infectivity by two stunt pathogens in L. maculigera will aid in the outlining of management strategies for this insect vector.

Meloidogyne incognita (root-knot nematode) is one of the most destructive pests of crops worldwide. Injudicious use of synthetic nematicides has led to environmental toxicity, development of resistance, and disruption of ecological balance, necessitating the need for safer and effective alternatives. Essential oil from Mentha spicata (Spearmint) has been reported to have nematicidal activity but the activity of its polar constituents is unexplored against the nematodes, infesting agricultural crops. Six compounds, stigmasterol (1), β-sitosterol-3-O-β-D-glucoside (2), 3β,13β-dihydroxy-urs-11-en-28-oic acid (3), 5,6-dihydroxy-7,8,4′-trimethoxyflavone (4), 5,6,4′-trihydroxy-7,8,3′-trimethoxyflavone (5), and 5,6,4′-trihydroxy-7,8-dimethoxyflavone (6), were isolated from methanolic extract of Mentha spicata (spearmint) and identified by NMR (1D & 2D) spectral analysis. Compound 3 was identified for the first time from genus Mentha. In vitro nematicidal activity of pure compounds (2 and 4–6) was carried out against Meloidogyne incognita, and results showed significant mortality (LC₅₀ values ranging between 62.64 and 74.19 ppm after 96 h). Molecular docking study revealed the favourable binding of the test compounds with acetylcholinesterase enzyme, facilitated by H-bond, electrostatic interactions, and hydrophobic interactions. The binding energy of the tested compounds with the target protein was found highest in 5 (− 10.0 kcal/mol) and 6(− 9.9 kcal/mol) followed by 2 (− 9.2 kcal/mol) and 4 (− 8.9 kcal/mol). The minimum binding energy was recorded in carbofuran (−7.5 kcal/mol), a positive control, and was also corroborated with in vitro nematicidal activity. This study showed the potent nematicidal activity of compounds (2 and 4–6), which can be further used for the development of nematicides against M. incognita in agriculture.

Fungi of the Ceratocystis fimbriata complex are important pathogens in woody species, associated with symptoms of wilt, stem lesions and death of infected plants. In Eucalyptus plantations, these pathogens can reduce productivity and cause high mortality in the first years of planting. The objective of this work was to evaluate the symptoms and characterize isolates of Ceratocystis associated with Eucalyptus plantations in southern Bahia, Brazil. In this study, we observed that external symptoms manifested mainly in trees with up to 36 months of planting; however, asymptomatic diseased trees were found until the end of the cycle (7 years). Symptoms of wilt, wood discoloration, formation of adventitious shoots and bark lesions, and drying of branches and death have been observed in diseased trees. The discoloration of the wood began in the root system, which is probably the point of penetration of the causal agent. Symptoms of heartwood rot, along with the characteristic wood discoloration of Ceratocystis wilt, were observed in some of the diseased trees. Based on the sequencing of the rpbII, ms204 and bt1 gene regions, the Ceratocystis isolates obtained from diseased trees were identified as belonging to the species C. manginecans. The morphological characteristics and optimal development temperature of the studied isolates are consistent with those described in the literature for this pathogen. Although collected from geographically close locations, the Ceratocystis isolates studied exhibited different levels of aggressiveness against Eucalyptus clones. This result illustrates the difficulty in selecting materials resistant to Ceratocystis wilt. The present work improves the understanding of Ceratocystis wilt in Eucalyptus and its causal agent.

Sunflower, a highly cross-pollinated crop, relies significantly on both Apis and non-Apis bees for pollination. However, insect pests often necessitate pest management practices, which, while targeting pests, inadvertently disrupt pollinator foraging and visitation, resulting in reduced yields. Recognizing this, the impact of pest management modules on sunflower cultivation was studied, focusing on major insect pests, pollinators, and natural enemies. Over a two-year study, conducted at Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu (SKUAST-J), two major insect pests, Helicoverpa armigera, and Spodoptera litura (Noctuidae: Lepidoptera), alongside twenty-five pollinating bee species and five natural enemies were recorded within the sunflower ecosystem. Four pest management modules (M-I: deep plowing + hand picking + pheromone traps @ 4/acre + bird perches @ 10/acre + alternative spray of Bacillus thuringiensis @2 ml/lit and Spinosad 45 SC @0.2 ml/lit; M-II: deep plowing + hand picking + pheromone traps @ 4/acre + bird perches @ 10/acre + blanket spray of Neem oil @5 ml/lit and Beauvaria bassiana @ 2 ml/lit; M-III: deep plowing + hand picking + pheromone traps @ 4/acre + bird perches @ 10/acre + alternative spray of emamectin benzoate 5 SG @ 0.4 g/lit + chlorantraniliprole 18.5 SC @0.3 ml/lit; M-IV: control) were evaluated for their efficacy against major insect pests, bee visitation, and natural enemy populations. Module-III emerged as the most effective, reducing larval counts of H. armigera and S. litura by 81.05% and 82.98% over the control, respectively, comparable to Module-I. However, bee visitation varied among modules, with Module-III consistently exhibiting the lowest mean values and substantial reductions compared to the control (56.73%). Dynamics of natural enemies revealed significantly higher predator populations and parasitization rates in modules using non-synthetic chemical insecticides, namely Module-IV (control), Module-I, and Module-II, compared to Module-III. Seed yield analysis highlighted Module-I as the most influential, showcasing a 215.95% increase over the control, underscoring its agronomic and economic superiority (cost–benefit ratio: 1:1.89). These findings emphasize the importance of integrating non-synthetic chemical insecticides into pest management strategies to effectively combat major insect pests, yielding higher returns while maintaining harmony among pollinator and natural enemy populations.

This study aimed to evaluate the competitive ability of various maize, bean, and soybean cultivars when coexisting with different densities of Amaranthus hybridus, using a replacement series experiment conducted in completely randomized blocks with four replicates. The competitors included four maize cultivars, four bean cultivars, and two soybean cultivars, all tested against A. hybridus. The replacement series consisted of relative crop-to-A. hybridus ratios of 100:0, 75:25, 50:50, 25:75, and 0:100%, corresponding to 20:0, 15:5, 10:10, 5:15, and 0:20 plants per pot, respectively. Competitive ability was assessed using diagrams and relative competitiveness indices. Fifty days after plant emergence, the morphophysiological characteristics of the competing species were determined. Results indicate a negative impact on all species, with both the crop plants (maize, beans, and soybeans) and A. hybridus suffering due to competition for the same environmental resources. Interspecific competition was found to be more detrimental than intraspecific competition. Maize and bean cultivars showed greater competitive ability against A. hybridus, whereas soybeans were more adversely affected by the presence of the competitor.

Background

The privileged geographical position of Morocco as a Mediterranean country confers upon it a pivotal role in both regional and global food security. Leveraging its diverse geography and varying climate, the country contributes significantly to the worldwide supply chain by cultivating a wide array of crops. However, the extensive use of chemicals in the production process, particularly for pest management, has led to substantial degradation of environmental resources. Plant parasitic nematodes (PPNs) pose a significant threat to agricultural productivity, causing considerable crop yield losses. With growing concerns about the environmental and human health impacts of nematicides, restrictions on their usage have prompted the exploration of alternative control strategies for effective safe PPNs management.

Main body

The present review provides a comprehensive overview of research on plant parasitic nematodes (PPNs) in Morocco. It covers PPN taxa inventory, diversity, prevalence on different crops, and responses to environmental factors. The review also maps the distribution of the most dangerous genera, analyzes biological control methods for root knot nematodes Meloidogyne particularly, and identifies gaps and future research needs for sustainable PPN management. A total of 61 genera of PPNs were identified in Morocco, with Meloidogyne spp. being the most prevalent and dangerous genus, posing a serious threat to crop production in the country. The extensive distribution of PPNs, notably root knot, may be attributed to factors such as contaminated plant material and a lack of farmer awareness. Biological agents from Morocco’s ecosystems, including plant extracts, nematophagous fungi, and entomopathogenic nematodes, showed great potential as control agents for root knot nematodes. This review significantly contributes to Mediterranean and global nematological knowledge by providing insights into the diversity and sustainable management of plant parasitic nematodes.

Conclusion

The biological richness of Moroccan ecosystems can provide valuable resources for researchers in developing commercial effective bionematicides for plant pests.

Jambu plants (Acmella oleracea) exhibiting necrotic angular leaf spots were collected in Belém—Pará, Brazil. Suspected to be a disease caused by nematodes, the jambu leaves were processed and the presence of nematodes from Aphelenchoides genus was observed using a light microscope. These nematodes were reared on Fusarium sp. and subsequently morphologically and molecularly characterized to species level. Aphelenchoides sp. associated with jambu exhibited morphological and morphometric characteristics similar to those within the A. besseyi complex (A. besseyi sensu stricto, A. oryzae and A. pseudobesseyi). Still, these characteristics were insufficient to confirm the identity of this population. However, the Bayesian inference analysis, utilizing the expansion segment of the large subunit (D2-D3 LSU) of nuclear ribosomal DNA, yielded results with a high posterior probability, indicating that the Aphelenchoides sp. associated with jambu belongs to the A. pseudobesseyi species. Under controlled conditions, the reproduction of the nematode in the leaf tissues (RF > 1) was observed, resulting in disease symptoms. The highest reproductive rate of A. pseudobesseyi (RF = 2.6) was observed from inoculation with 100 nematodes per leaf (500 nematodes per plant). Based on Seinhorst analysis, the tolerance limit in jambu plants infected with A. pseudobesseyi was 250 nematodes. It is concluded that A. pseudobesseyi is the etiological agent of the jambu angular leaf spot. For future evaluation of jambu resistance on A. pseudobesseyi, an inoculate maximum of 100 nematodes per leaf is recommended.

The main objective of this study was to estimate and compare substitution matrixes of nucleotide frequencies for Tomato leaf curl New Delhi virus (ToLCNDV) with recently identified begomoviral isolates from two medicinal false daisy (Eclipta prostrata) and tomato (Solanum lycopersicum) plants. The ToLCNDV has become a significant limitation to vegetables production in many countries. A polymerase chain reaction was conducted to conserve the existence of begomoviral infection. The acquired amplicon was amplified using primers appropriate to the sequence in order to retrieve the full genome. The sequence analysis has confirmed the presence of ToLCNDV in symptomatic plants. The complete genome sequence having a 2.6–2.7 kb entire genome of ToLCNDV was obtained. An investigation of the phylogenetic and evolutionary history has verified the connection between this virus and other closely related viruses. The available nucleotide frequencies of codon regions (A, T/U, C, G) with newly isolates revealed 20–28% substitution matrixes. There was a minimal difference of nucleotide frequencies’ with already submitted database of this virus. Substitution matrixes, which quantify the probability of nucleotide substitutions evolving over a period of time, offer valuable information about mutation patterns and the forces driving evolution. This comparative analysis enhanced the comprehension of the genetic diversity of ToLCNDV and its possible consequences on medicinal plants. It also assisted in the formulation of efficient control measures and the preservation of begomoviruses in medicinal plant biodiversity. The information presented here is highly valuable for understanding the ToLCNDV biology and epidemiology, and it would also assist in disease management in the future.