Biologia do desenvolvimento, crescimento e controle de Dactyloctenium aegyptium (L.) Willd

Abstract

The species Dactyloctenium aegyptium (L.) Willd . (crowfootgrass) is found on five continents, among the species of the genus, it is amongsrt the 20 most widespread among weeds, compromising the agricultural production of 19 crops in 45 countries. In Brazil, it is found in an area with different management of sugarcane and its seeds present in several layers of the soil seed bank, and its management is extremely important to reduce the harmful effects on crops of economic interest. Domains of the physiology of its growth is essential for adopting control strategies and showing the best time to intervene in the weed. Therefore, the objective of this work was to evaluate the growth of crowfootgrass and to choose effective herbicides for its control in times of greater susceptibility. Seeds were collected in different environments, management and cultures, and three experiments were set up at the UFAL Engineering and Agricultural Sciences Campus, Rio Largo, AL. Experiment 1 was carried out in pots arranged in the field, using a randomized block design in a factorial scheme (4x 6) with five repetitions, the factors being populations of D. aegyptium (Traipu. Usina Coruripe, Santana do Mundaú and Rio Largo) and 6 evaluation times (15, 30, 45, 60, 75 and 90) days after transplantation DAT). The development, accumulation and distribution of dry mass and growth rates were evaluated. Subsequently, two simultaneous experiments were set up with a mix of six populations. Experiment 2 evaluated the efficacy of D. aegyptium control with pre- emergence herbicides conducted in a greenhouse with a randomized block design with four replications composed of 15 treatments, having one without application (control) and experiment 3 evaluated the suppression of D. aegyptium imposed by herbicides applied in post-emergence at three stages of development, based on the results of experiment 1. It was carried out in pots distributed in the field in a factorial arrangement (5 x 3) with four replications, the factors corresponding to 5 treatments of herbicide having a control (no application) combined in three growth stages (initial post-emergence, tillering and flowering. The plants of D. aegyptium , showed growth peak between 30 and 45 DAT, reaching greater leaf area, growth rates and dry mass accumulation The herbicide oxyfluorfen, isolated and mixed with diuron , showed 100% efficacy in pre- emergence control in all evaluation periods up to 6 3 days after application (DAA) and the less effective herbicides diclosulam and hexazinone with control below 6.2% at 63 DAA and greater accumulation of weed dry mass. The best control and post-emergence efficacy was obtained in the control times proposed in the conclusions of experiment 1, in the initial post-emergence before the beginning of the growth peak and at the beginning of flowering when there is a greater reduction in dry mass and in the roots, contributing to less reserve and low weed regrowth capacity. Keywords: Dactyloctenium aegyptium; crowfootgrass; chemical control