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Efeito residual e tempo de exposição à abamectina em Aceria guerreronis Keifer: implicações do uso de adjuvantes em campo

Wed, 01 Jan 2025 00:00:00 GMT

Título: Efeito residual e tempo de exposição à abamectina em Aceria guerreronis Keifer: implicações do uso de adjuvantes em campo Autor(es): Moura, Wesley da Silva Abstract: Controlling Aceria guerreronis Keifer in coconut crops is a challenge for producers, as the growth of colonies on bracts protects them from contact with acaricides. Therefore, control depends on the contamination of mites during their dispersal by the residual effect of applied products, and the addition of adjuvants can improve this effect, even prolonging it. This study aimed to determine the contamination time of the commercial product VERTIMEC® 18 EC (Abamectin) on A. guerreronis to cause mortality and to evaluate the effect of adding adjuvants on its residual time in the field. For the bioassay for exposure time and mortality in the laboratory, experimental arenas with leaflet fragments (2x4 cm) were immersed in VERTIMEC® 18 EC (300 ml/ha) and control (distilled water) treatments, and left to dry exposed to air for 20 minutes. Then, 30 larger A. guerreronis individuals were transferred and exposed to waste for 15 min, 30 min, 60 min, and 120 minutes. After each time point, the mites were transferred to a new experimental arena with a fragment without product, and mortality was evaluated after 12 hours. For the residual time bioassay in the field, 4 plants were sprayed with the following treatments: Negative control (water only), Positive control (VERTIMEC® 18 EC (300 ml/ha)), VERTIMEC® 18 EC + Silwet 0.25% v/v, and VERTIMEC® 18 EC + Speed Oil 0.25% v/v. Leaflets were collected at 24h, 72h, and 144h after spraying to set up the experimental units. Thirty of the largest A. guerreronis individuals were transferred, and mortality was assessed after 12h. For the contamination time bioassay, the mortality rate differed significantly between treatments (χ² = 82.33; df = 4; p < 0.001), with the 120-minute treatment showing significantly higher mortality than all others. For the field bioassay, the Vertimec and Vertimec + Speed Oil treatments, 144 h after application, showed a significant difference in mortality (χ² = 16.50; df = 2; p < 0.001), where the VERTIMEC® 18 EC treatment showed significantly higher mortality than the control (p = 0.005), while VERTIMEC® 18 EC + Speed Oil did not differ from the control (p = 0.447). For the VERTIMEC® 18 EC + Silwet AG treatment, the mortality rate differed significantly between treatments 24 h after the interval (χ² = 28.34; df = 1; p < 0.001), showing significantly higher mortality compared to the control, a result corroborated by the Wilcoxon rank-sum test (W = 34.5; p < 0.001). However, 72 hours after the date, no statistically significant difference was detected in the mortality rate between the control (χ² = 3.68; df = 1; p = 0.055). Abiotic factors such as rainfall can influence the persistence of products with different bases in ways that are not yet fully understood, especially when they occur less than 24 hours after the explosion, weakening the efficiency of the applications. However, more studies are needed to understand how the interaction between the spray solutions and these factors occurs, so that strategies can be developed to mitigate it . Tipo: TCC

Phenotypic stratification of corn stunt tolerance in a tropical public maize panel reveals contrasting extreme phenotypes

Thu, 01 Jan 2026 00:00:00 GMT

Título: Phenotypic stratification of corn stunt tolerance in a tropical public maize panel reveals contrasting extreme phenotypes Autor(es): Lima, Thiago de Oliveira Abstract: Corn stunt is one of the most important diseases affecting maize (Zea mays L.) production in tropical regions of the Americas and is caused by a complex of pathogens transmitted by the corn leafhopper (Dalbulus maidis). The quantitative nature of tolerance to this disease, combined with strong environmental effects and heterogeneous infection pressure under field conditions, poses major challenges for the identification and selection of superior genotypes. The objective of this study was to perform phenotypic stratification of corn stunt tolerance in a tropical public maize panel in order to identify extreme phenotypes and support future genomic analyses. A total of 360 inbred lines were evaluated under natural infection using three complementary traits: sanity score in survivor plants, proportion of survivor plants, and whole sanity score. Substantial phenotypic variation was observed among lines, with continuous trait distributions, confirming the quantitative inheritance of corn stunt tolerance. Phenotypic stratification allowed the identification of highly tolerant and highly susceptible genotypes, indicating the presence of favorable allelic combinations within the evaluated germplasm. The proposed approach proved effective for characterizing genotype responses to corn stunt and provides a robust phenotypic foundation for extreme phenotype–based genome-wide association studies, in addition to contributing to the identification of potential parental lines to be used in breeding programs, contributing to maize breeding efforts aimed at improving tolerance to insect-vectored diseases in tropical environments. Tipo: TCC

Herança genética da resistência por antibiose à mosca-minadora na linhagem de meloeiro EATMEL 20230024

Thu, 01 Jan 2026 00:00:00 GMT

Título: Herança genética da resistência por antibiose à mosca-minadora na linhagem de meloeiro EATMEL 20230024 Autor(es): Silva, Sávio Eufrásio da Abstract: The leafminer fly (Liriomyza sativae Blanchard) is one of the main pests of melon (Cucumis melo L.), causing significant damage to the crop and increasing production costs due to the intensive use of insecticides. In this context, genetic resistance constitutes a sustainable alternative for managing this pest. The present study aimed to elucidate the genetic inheritance of antibiosis resistance to the leafminer fly in the melon line EATMEL 20230024. To this end, a population was structured from the cross between the resistant line EATMEL 20230024 (P1) and the susceptible line EHMEL 200910 (P2). Parental generations (P1 and P2), filial generations (F1 and F2), and backcrosses (RC1 and RC2) were evaluated under cage and field conditions, considering the number of mines per plant, larval and pupal viability of the insect, and the phenotypic classification of the plants regarding resistance. Statistical analysis, performed using the GENES program, employed the Chi-square test to assess the fit of the data to the proposed genetic models. The results showed phenotypic uniformity in the F1 generation, an approximate segregation of 3:1 in F2, and 1:1 in the backcross with the susceptible parent, confirming that resistance is controlled by a single dominant gene. The reduction in larval and pupal viability of the leafminer fly in resistant plants indicated that the resistance mechanism acts predominantly through antibiosis, with no antixenosis-type resistance observed. Validation under field conditions confirmed the stability of the trait expression. It is concluded that the genetic inheritance of the EATMEL 20230024 lineage is conditioned by a single gene with two alleles and a complete dominance relationship, constituting a promising source of genetic resistance to L. sativae, with potential application in melon breeding programs and integrated pest management strategies. Tipo: TCC

Levantamento fitossociológico de plantas daninhas na cultura do coqueiro na empresa Cohibra, Amontada-CE

Thu, 01 Jan 2026 00:00:00 GMT

Título: Levantamento fitossociológico de plantas daninhas na cultura do coqueiro na empresa Cohibra, Amontada-CE Autor(es): Ferreira, Tatiane Maria Sampaio Abstract: The phytosociological survey of weed species is a fundamental tool for understanding the dynamics of weed communities in agricultural systems, especially in perennial crops such as coconut. This study aimed to conduct a survey of the weed species present in the coconut seed production area of the company COHIBRA, located in the municipality of Amontada, Ceará, Brazil. The evaluated area corresponds to a coconut plantation of the Green Dwarf variety from Jiqui, managed under an irrigated system with intensive management. Sampling was carried out through the random placement of inventory quadrats within the projection of the coconut tree canopy, a region considered the most representative of infestation due to greater water availability. The collected species were identified and classified according to botanical families, growth habits, and reproduction forms. Subsequently, the phytosociological parameters of frequency, density, abundance, importance value index, and relative importance were analyzed. Sixteen weed species were identified, distributed among 12 botanical families, belonging to the monocotyledonous and eudicotyledonous classes, with emphasis on the Poaceae, Cyperaceae, and Asteraceae families, which are commonly observed in agricultural areas. Among the identified species, Cyperus spp., Commelina benghalensis L., and Cyperus aggregatus (Willd.) Endl. presented the highest importance value index values, thus being the main contributors to infestation in the area. The results indicate that the adopted management practices, combined with edaphoclimatic conditions and the irrigation system, directly influence the composition and structure of the weed community. Therefore, the phytosociological survey proved to be essential for supporting more efficient integrated weed management strategies, aiming to reduce weed pressure, optimize production costs, and promote the sustainability of the production system. Tipo: TCC