Renan Ricardo Zandoná

In cropping systems, the persistence of weed seed banks is a major challenge for sustainable weed management. This study aimed to evaluate the efficiency of pre-sowing and post-emergence herbicide management, combined with pre-harvest physical control, in reducing the ryegrass and wild radish seed bank over five seasons in a wheat-soybean succession. The experiment was conducted in a randomized complete block design with a split-plot arrangement. The seed bank evaluation periods (November 2021, July 2022, and November 2022) were allocated to the main plots, and four desiccation management strategies were allocated to the subplots: glyphosate (900 g ha-1); glyphosate + clethodim (900 + 120 g ha-1); glyphosate + saflufenacil (900 + 35 g ha-1); glyphosate + clethodim + saflufenacil (900 + 120 + 35 g ha-1). For the latter treatment, the remaining plants were manually uprooted prior to harvest. The chemical control alone, regardless of herbicide combinations, was ineffective in reducing the ryegrass and wild radish seed bank after five years of cultivation. In contrast, the integration of herbicide applications and manual weed removal was the most effective strategy, resulting in improved weed control and higher wheat grain yield. Increasing weed infestation over time in areas under exclusive chemical desiccation management compromised the wheat grain production, rendering harvest unfeasible.

Background: Hairy beggarticks (Bidens pilosa L.) is a highly adaptable weed species that thrives in diverse environmental conditions. Understanding the environmental factors that influence its germination is essential for developing predictive emergence models and supporting integrated management strategies. Objective: The present study aimed to estimate the cardinal temperatures and water potentials for B. pilosa germination, assess seed bank longevity, and develop a field-based emergence model. Methods: Laboratory experiments were conducted to determine base temperature and water potential thresholds for [...] Abstract Background: Hairy beggarticks (Bidens pilosa L.) is a highly adaptable weed species that thrives in diverse environmental conditions. Understanding the environmental factors that influence its germination is essential for developing predictive emergence models and supporting integrated management strategies. Objective: The present study aimed to estimate the cardinal temperatures and water potentials for B. pilosa germination, assess seed bank longevity, and develop a field-based emergence model. Methods: Laboratory experiments were conducted to determine base temperature and water potential thresholds for

Background: Ryegrass is considered an important weed in crops in the state of Rio Grande do Sul, Brazil, for being resistant to the herbicide glyphosate. Objective: This study evaluates ryegrass control by applying different spray volumes and doses of clethodim alone or in combination with glyphosate and/or 2,4-D. Methods: Two field experiments were conducted in a 5 x 3 factorial design. In experiment I, factor A consisted of clethodim (96 g a.i. ha-1); clethodim (96 g a.i. ha-1) + [...] Background: Ryegrass is considered an important weed in crops in the state of Rio Grande do Sul, Brazil, for being resistant to the herbicide glyphosate. Objective: This study evaluates ryegrass control by applying different spray volumes and doses of clethodim alone or in combination with glyphosate and/or 2,4-D. Methods: Two field experiments were conducted in a 5 x 3 factorial design. In experiment I, factor A consisted of clethodim (96 g a.i. ha-1); clethodim (96 g a.i. ha-1) +

Conyza spp. é uma espécie de difícil controle, principalmente quando se encontram com maior estatura e em estádios mais avançados de desenvolvimento. O estudo objetivou avaliar a eficiência de controle de 2,4-D colina e da mistura formulada de 2,4-D colina e glifosato em Conyza spp. com diferentes estaturas e estádios de desenvolvimento. Os fatores avaliados foram três estaturas de Conyza spp. (1-2; 10-12 e 25-30 cm); dois herbicidas [2,4-D colina (EC) e 2,4-D colina + glifosato (ED)]; e doses destes herbicidas correspondentes a 0x, 1/2x, 1x, 2x e 4x a dose recomendada. O herbicida ED proporcionou melhor controle comparativamente ao EC em todas as doses e estaturas avaliadas. O controle de Conyza spp. deve ser realizado em estágios iniciais de desenvolvimento, pois ambos os herbicidas nas doses iguais ou superiores as doses de registro são eficazes para o controle, o que não ocorre em estatura maiores que 10 cm ou estágio de 19 folhas.

Peach tree thinning is essential to harvest quality fruits and to keep balanced production for several years. Manual thinning of peach trees demands much work force and increases production costs. Chemical thinning may be an alternative solution, but efficiency depends on doses and species. This study aimed at evaluating the effect of metamitron – applied at different concentrations – on chemical thinning of peach trees in the south of Brazil. The experiment was carried out in a commercial peach tree orchard where ‘Sensação’ cultivars, in Morro Redondo, Rio Grande do Sul (RS) state, Brazil. The following metamitron concentrations were applied at concentrations of 100 mg L^-1, 200 mg L^-1, 300 mg L^-1, 400 mg L^-1, manual thinning was carried out 40 days after full bloom (DAFB) and to the treatment where the plants have no thinning. Fruit abscission, effective fructification, total number of plants per plant, production per plant, mean mass and fruit diameter were evaluated. Concentrations of 300 and 400 mg L^-1 metamitron 40 DAFB provides promoted high fruit abscission, besides decreasing the number of fruits and production. Therefore, concentrations of 100 and 200 mg L^-1 of metamitron 40 DAFB provides results in an efficient thinning practice similar to manual thinning for production, mass and fruit diameter.

Introduction A. hybridus interference in soybeans varies with population size and may be quantified by mathematical models that allow establishing the threshold levels. Objective Determine the interference of A. hybridus escaped from an herbicide program and with multiple resistance to EPSPs and ALS-inhibiting herbicides on soybean yield and its economic threshold (ET). Methods Two experiments were conducted in a randomized block design. The treatments consisted of populations of A. hybridus ranging from 0 to 41 plants m-2 (2018/19) and [...] Abstract Introduction A. hybridus interference in soybeans varies with population size and may be quantified by mathematical models that allow establishing the threshold levels. Objective Determine the interference of A. hybridus escaped from an herbicide program and with multiple resistance to EPSPs and ALS-inhibiting herbicides on soybean yield and its economic threshold (ET). Methods Two experiments were conducted in a randomized block design. The treatments consisted of populations of A. hybridus ranging from 0 to 41 plants m-2 (2018/19) and

The objective of this work was to evaluate the effect of chemical thinning with metamitron on fruit of the Maciel and Sensação peach (Prunus persica) tree cultivars, as well as to identify its relation to the carbohydrate content in their branches. The experimental design was randomized complete blocks, and the treatments were trees with no thinning, manual fruit thinning, and chemical thinning with 200 mg L-1 metamitron applied at 20, 40, and 60 days after full blooming. The evaluated variables were: abscission percentage, yield per plant, number of fruit, presence of lignin in fruit, and carbohydrate content in the branches. The carbohydrate content was evaluated in trees with and without chemical thinning seven days after the application of the product. The use of metamitron promotes fruit thinning in the ‘Maciel’ and ‘Sensação’ peach trees, with a decrease in the carbohydrate content in their branches. Metamitron application 20 and 40 days after full blooming favors fruit abscission in both studied cultivars.

Barnyard grass (Echinochloa sp.) is one of the main rice weeds. Knowledge of its emergence can support management measures. The present study models barnyard grass emergence at different flooded rice sowing periods. Furthermore, the effectiveness of the hydrothermal time model in estimating barnyard grass emergence is analyzed. Field emergence was monitored three times a week during two sowing times (October and November) and two growing seasons (2017/18 and 2018/19), in rice sown and unsown areas. Data were converted to cumulative emergence based on total seedlings. Soil temperature and moisture data were used to determine hydrothermal time. The sowing in October led to a continuous emergence of barnyard grass, while the sowing in late November led to different emergence rates. The highest emergence rates of barnyard grass occur in the first sowing time. The hydrothermal time model is adequate to estimate barnyard grass emergence in both sowing times.