Estratégias de manejo da ferrugem asiática da soja e seu efeito sobre a severidade da doença e o desempenho da cultura

Abstract

During the soybean cycle, diseases such as Asian rust (Phakopsora pachyrizi) can bring economic losses to the producer, due to the reduction of grain yield, if management strategies are not adopted properly. The objective of this work was to evaluate different management strategies to minimize the harmful effects of Asian soybean rust on the agronomic performance of the crop. The research was carried out in the Experimental Area of UTFPR, Câmpus Dois Vizinhos, in the 2016/17 and 2017/18 crops. The tested cultivars: NS 5909 (susceptible to Asian rust), LG 60163 (tolerant) and TMG 7062 (resistant). The plants were submitted to fungicide applications, foliar fertilizers based on copper and potassium phosphites, with sprays in two phenological stages, R1 (beginning of flowering) and R5 (beginning of grain filling). The Asian rust severity assessments were performed on R1, and repeated every 14 days (up to 14 after R5), with three plants per plot in the lower, middle and upper thirds and the general average per plant to determine the Area Under the Disease Progression Curve (AUDPC) of both. The experimental design was a randomized block design, with three replications. Data submitted to analysis of variance, and compared by the Duncan test, at 5% probability. Isolated use of the fungicide reduced the AUDPC in both cultivars, without statistical differences of productivity. Use of fungicide and foliar fertilizers based on copper and potassium phosphite, when applied together reduced the AUDPC in cultivar NS 5909, susceptible. The isolated application of foliar fertilizers based on copper and potassium phosphite did not reduce the AUDPC of the respective cultivars. Comparing cultivar NS 5909 (susceptible), LG 60163 (tolerant) and resistant (TMG 7062) to Asian soybean rust, the results show that the cultivar with genetic resistance (TMG 7062) presented lower AUDPC of the disease, followed by the cultivar tolerant (LG 60163), even so in the two experiments productivity did not differ statistically among the cultivars. At harvest, the following variables were evaluated: plant height, height of first pod insertion, number of pods, number of grains per plant, number of grains per pod, mass of one thousand grains and productivity for both cultivars, with productivity did not differ between treatments and cultivars.