Neotropical Entomology最新文献

Insects, due to their unrestricted reproduction, have been a long-known nuisance causing significant damage to various crops. Besides the synthetic chemical pesticides, the bioactive compounds derived from medicinal plants also make a positive contribution against the control of pests. In this concern, the present study investigated the biological activity of essential oil and isolated sesquiterpene alcohols, τ-cadinol and β-bisabolol, from Clausena indica leaves against three insect pests, Spodoptera litura, Helicoverpa armigera, and Tribolium castaneum. Four different concentrations (25, 50, 75, and 100 g L^-1) of oil, τ-cadinol, and β-bisabolol in both normal and microencapsulated forms were tested for their efficacy in the field trial. Among all the compounds, τ-cadinol exhibited strong toxicity (LD₅₀ = 35.93-52.94 µg larva^-1), antifeedant activity (DC₅₀ = 52.51-75.93 µg cm^-2), and oviposition deterrent activity (OD₅₀ = 56.73-67.18 µg cm^-2) against all the tested pests followed by β-bisabolol and leaf essential oil. Additionally, both the compounds demonstrated noteworthy acetylcholinesterase inhibitory activity with IC₅₀ values of 24.53-30.98 μg mL^-1 and 32.15-40.41 μg mL^-1 respectively comparable to the positive control, galantamine. Moreover, both τ-cadinol and β-bisabolol exhibited the strongest cytotoxicity against Sf9 cells lines with IC₅₀ of 15.27 and 17.82 µg mL^-1 respectively while IC₅₀ of 5.02 µg mL^-1 was shown by azadirachtin on the same cell line. Results of the field trial reveal that all tested compounds showed considerable mortality of S. litura and H. armigera. Although the treatments showed good insecticidal activity in the field trial, but modifications are required for the concentration of active ingredients in the formulation or even in the formulation to enhance the effect. The results obtained lay a foundation for future field applications of oil and isolated compounds as crop protectants.

Diamondback moth, Plutella xylostella (L.), is a major pest of cruciferous crops, whereas Aphis craccivora is a major sucking pest of leguminous crops. Indiscriminate use of synthetic insecticides for the control of insect pests leads to insecticide resistance, harmful to natural enemies of pests, pollinators, the environment, and consumers' health. Therefore, it is necessary to screen/identify alternate strategies to control the target pests. Steroidal saponins, a group of specialized amphiphilic metabolites, are known for their various biological properties. There are a few reports on insecticidal activities of steroidal saponins. In the present study, insecticidal activities of nine diverse steroidal saponins isolated from Trillium govanianum were evaluated against Plutella xylostella and Aphis craccivora. Among the molecules, govanoside E (3) was found more effective against Plutella xylostella (LD₅₀ = 0.91 µL/insect) after 96 h of treatment followed by govanosides D and F (1.44 and 1.56 µL/insect, respectively). Similarly, govanoside E was also found effective against Aphis craccivora (LD₅₀ = 1.04 µL/insect) followed by dehydroxy-diosgenin and pennogenin-triglycoside (1.19 and 1.36 µL/insect, respectively). Furthermore, govanoside E (3) showed promising repellency (RC₅₀ = 1043.20 µL/L) against Plutella xylostella. The molecules also showed a dose-dependent relationship with inhibitory effects on the reproduction of Aphis craccivora. In vitro enzyme inhibition/mechanism study confirmed that govanoside E (3) inhibited glutathione-S-transferase (GST) and carboxylesterase (CES1) in test insects. The present study suggested the potential utilization of steroidal saponins for the control of target pests based on field bio-efficacy results.

The genus Chrysomela includes several species known to be pests of willow (Salix spp.) and poplar (Populus spp.) trees, primarily distributed across North America. However, these species are expanding beyond their natural range. This study presents the first record of C. scripta in Colombia where it feeds and reproduces on Salix humboldtiana; additionally, this species is also recorded for the first time from Ecuador and Peru based on participative science records; furthermore, another species, C. texana, is also recorded from Colombia. The introduction of these species raises concerns for timber-producing regions, particularly in Argentina and Chile, and on the existing pressures on Salix humboldtiana, the only native species of this genus in the region.

Introgressive hybridization involves the integration of genetic material from one population into another genetically distinct population. Despite its widespread occurrence in nature, the mechanisms and consequences of introgression remain poorly understood. In this study, we examine the hypothesis that the mitochondrial gene COI from Drosophila antonietae has been introgressed into the gene pool of a specific population of D. gouveai. Additionally, we extended our analysis to include other genes associated with the COX complex, such as mitochondrial (COII) and nuclear genes (CoVa, CG9603, and levy), across various populations of both species from different locations. We estimated indices of genetic diversity, constructed haplotype networks in both mitochondrial and nuclear genes, and performed selection tests to assess the evolutionary dynamics of mitochondrial genes. Our results confirm the hypothesis of a historical secondary contact between D. gouveai and D. antonietae in the region of Analândia, SP, showing asymmetric unidirectional introgression, with signs of positive selection in the mitochondrial genes.

Here, we studied Askola specimens sampled from streams in the Caatinga and Atlantic Forest ecoregions of Brazil. We associate nymphs and adults of A. mucuge using molecular tools (COI sequences). The nymph of this species can be differentiated from the two other known nymphs of the genus by the internal denticle medially located at the external incisor of the left mandible and by abdominal terga without marks. In addition, Automatic Barcode Gap Discovery revealed the possibility of cryptic species under the name of Askola froehlichi, suggesting three independent lineages. Our results reduce the Haeckelian and Linnean shortfalls for Askola, since we describe the third nymph of the genus and shed light on the possibility that the most widely distributed Askola species includes putative cryptic species.

Tetranychus urticae Koch is a major pest in cotton crops; in Brazil, the predatory mite Neoseiulus californicus (McGregor) is used for its biological control. Although the standard recommendation for controlling T. urticae is to release around 20,000 individuals per hectare, this is a general guideline and may not be suitable for cotton crops. The present study examined the effect of N. californicus on T. urticae populations in semi-field conditions to identify the predator density needed to reduce pest infestation and the percentage of infested plants. We tested predator-to-prey ratios of 0:50, 3:50, 5:50, and 10:50 on cotton plants maintained in a greenhouse. Tetranychus urticae individuals and the proportion of infested plants were counted daily for the first 5 days, then every 3 days until day 29. All tested densities of N. californicus reduced T. urticae infestation; however, only the release of 5 or 10 predators per 50 T. urticae individuals resulted in infestation levels below the economic threshold level (ETL) recommended for controlling the two-spotted spider mite in cotton crops.

Commercially available in Brazil since the 2013/2014 crop season, the adoption of Bt soybean rapidly increased to > 80% after only eight crop seasons (2020/2021). The widespread use of Bt soybean has achieved regional suppression of key lepidopteran pests and reduced insecticide use, providing economic and environmental benefits for all in Brazilian agriculture. Due to the high efficacy of Bt soybean in controlling key soybean lepidopteran pests and the simplicity of its use, most soybean farmers have adopted Bt soybean in extensive areas, reaching 94% adoption in the 2023/2024 crop season. However, the high adoption of Bt soybean associated with low refuge compliance has led to the first cases of pest resistance to Cry1Ac (Crocidosema sp. and Rachiplusia nu) in Brazil, representing major challenges to the future of this technology. Unfortunately, farmers wrongly believe that non-Bt soybean cultivars cannot be as profitable and productive as Bt soybean cultivars. Therefore, more than 10 years after Bt soybean adoption in Brazil, this review discusses the most important benefits and challenges of Bt soybean use and what can be expected for the next decade of this technology.

Feltia repleta (Walker, 1857), popularly known as "greater cutworm" in the USA and Canada and "cortador grande" in Latin America, is an important pest species occurring throughout the Americas. The popular name refers to its size and the habits of the larvae, which frequently cut shoots of seedlings, causing severe injuries or death of the host plant. Despite its importance to crops management, the immature stages of this species were never described in detail; moreover, they are frequently confused with many other agrotines, specially with species of Feltia Walker, 1856 and Agrotis Oschenheimer, 1816. Therefore, this study aims to describe the external morphology and the tegument ultra-structure of the immature stages of Feltia repleta based on exemplars obtained from a female collected in Planaltina, Brasília, Distrito Federal, Brazil, whose larvae were fed with artificial diet. Descriptions of the morphology with illustrations are presented, based upon observations through scanning electron microscopy and stereoscopic and optic microscopes attached to a camera lucida. Descriptions and illustrations of the eggs, first and last instars head capsule, chaetotaxy, tegument, and setae, and both sexes pupae are presented and the morphological characters are discussed and compared with immature stages of other species of agrotines. Additionally, a comprehensive list of host plants and a geographic distribution map based both on literature and new data based on studied specimens are provided.

The Neotropical region is a vast and heterogeneous ecozone harboring diverse Drosophilidae Fallén 1823 species. However, these species' distribution patterns and climatic requirements are poorly understood. In this study, we aimed to estimate differences in the climatic niche and distribution patterns among species to test the hypothesis that endemic and cosmopolitan species occurring in the Neotropics present different climatic niches, such that distribution range and niche breadth are highly correlated among species. For this task, we evaluated the geographic distributions and the climatic niches of 47 endemic and cosmopolitan drosophilids occurring in subtropical regions of the Neotropics using raw climatic data from collection records and environmental niche models (ENMs). We showed that the studied species varied in two highly correlated properties: the distribution ranges and the environmental niche breadth. Moreover, significant differences were observed between endemic and cosmopolitan drosophilids in terms of variable importance and climatic niches. Most of the studied species are distributed in regions under mild climatic conditions, but there are many species inhabiting harsher environments. Generally, the results suggest that several Neotropical drosophilid species may be highly vulnerable to global warming, potentially serving as bioindicator species for assessing the impact of climate change.

Tetranychus urticae Koch (Acari: Tetranychidae), commonly known as the two-spotted spider mite, is a major polyphagous pest that affects a wide range of vegetable crops. Infestation of T. urticae is more prominent on eggplant which causes 50-80% yield loss if no control measures initiated. The economic threat posed by T. urticae is constantly increasing because of the development of pesticide resistance and resurgence. One of best alternative management strategies is use of plant-based pesticides like secondary metabolites and essential oils (EOs) which provides sustainable and long-term protection. In the present study, EO extracted from a billygoat weed, Ageratum conyzoides L. (Asterales: Asteraceae), and its binary compounds were evaluated against T. urticae. The A. conyzoides EOs showed highest mortality (97.5% with the LC₅₀ 10.61 µL/mL), due to the presence of Precocene I (32.32%), Geraniol (1.23%), and Neral (0.55%). Among the binary compounds, Geraniol (95%) showed highest mortality having LC₅₀ (95%) of 9.59 µL/mL followed by Citronellol (77.5%) and Alpha-pipene (75%). Significant increase in the activity of esterases, glutathione S-transferase, and acetylcholine esterases contributed for the toxicity in T. urticae following exposure to essential oils (EO) and their binary compounds. SEM images revealed shrinking of the bodies of treated T. urticae along with reduced body measurements compared to the untreated individuals. The present study indicates that A. conyzoides EO could be used for development of new acaricides for sustainable management of T. urticae.