Efeito da aplicação de fungicida protetor multissítio em diferentes épocas na cultura da soja

Abstract

The asian soybean rust, caused by the fungus Phakopsora pachyrhizi, is one of the main diseases that threaten productivity of soybean in virtually all regions. The application of fungicides is the tool most used and providing greater efficiency in the control of damage caused by the disease. The adoption of management strategies, such as the association of fungicides multissítios to place-specific, has contributed to increasing the effectiveness of the control of the disease and reducing the risk of the appearance of resistant populations of the pathogen, especially when applied at the right time, since the "beginning of control" is the key to increased efficiency of the products. In this way this purpose of this study was to evaluate the effect of the application of protective fungicide multissítio in different seasons in soybean culture. The experiment was conducted in the period between the months of December 2015 and April 2016, in the experimental area of Universidade Federal da Fronteira Sul – Campus Cerro Largo, situated in the northwest of the state of Rio Grande do Sul. The experiment was conducted in 3 x 3 factorial scheme (start times x control control programs) with four repetitions. The experimental design used was the random block (DBC). Fungicides were applied at three times, and each time were used three types of programs. The times were in the appearance of the first symptoms of the Asian rust, stadium V6 of culture and stadium R1 of soy culture. The programs used were: Program 1: first application - multissítio + site-specific, second application - site-specific and third application - site-specific; Program 2: first application - multissítio + site-specific, second application - multissítio + site-specific-place and third application - site-specific; Program 3: first application - site-specific, second application - site-specific and third application - site-specific. The multissítio fungicide used was mancozeb (1500 g a.i. ha-1) and the site-specific were Azoxystrobin + Cyproconazole (60 + 24 g ha-1) and Azoxystrobin + Benzovindiflupir (90 + 45 g ha-1). Evaluations were made of rust severity, level of defoliation in soybean plants and income components of culture. It was possible to conclude that the application of fungicide multissítio provided AACPD reduction of the rust, depending on the time when the control has been started and control program adopted, in the lower and middle thirds of the soybean plants, as well as on the productivity and number of pods per plant. As for the other components of income and level of defoliation, no significant interactions were observed.