Fosfito de potássio no manejo da ferrugem asiática da soja

Abstract

Asian Rust (Phakopsora pachyrhizi) causes up to 90% reduction in soybean production. Fungicides are the main form of disease control, but they suffer crop damage. Therefore, the use of potentiometer has been used as an alternative for the management of plant diseases. Thus, this study aimed to evaluate or control Asian soybean rust and research increments using two sources of potassium phosphite. The experiment was carried out in the experimental area of Unipampa / Campus Itaqui, in a randomized block design (DBC) with four treatments and five replications. For this, it was used to cultivate Don Mario 66i68, and two sources of potassium phosphites were used, a commercial fungicide and a control as treatment. Two applications of each treatment were performed, the first in R2 and the second in R5. Severity assessments began at seven days after the first application and occurred weekly in ten plants of each treatment. The upper, middle and lower third of the plant were evaluated separately. From the severity data, the area below the disease severity progress curve (AACPSD) was determined. Data were subjected to analysis of variance by the F test and means grouped by the Scott & Knott test (P≤0.05) using the Sisvar software. No disease incidence was observed in the upper third of the plant during the evaluations. In the middle third, it was found that fungicide was the most effective in reducing AACPSD, controlling the disease by 78.72%, followed by Phosphite¹ and Phosphite², which showed control percentages of 55.43 and 49.2%, respectively. The same occurred in the lower third, where the fungicide reduced 78.58% of the disease, followed by Phosphite¹ and Phosphite², with control of 44.45 and 52.26%. Regarding yield, the fungicide also showed 15% increments, followed by the two sources of phosphite, which showed increases of 7.2 and 6.97% in soybean crop yield. In evaluating the weight of one thousand soybeans, both sources of phosphite and fungicide showed the same behavior. The use of potassium phosphites decreases the severity of Asian rust leading to significant increases in crop yield increases.