Reflectance as a decision-making tool for the application of fungicide to the Asian Soybean Rust

Resumen

The objective of this study was to evaluate the application of GreenSeeker® (radiometer) the ideal time of application of fungicide on soybeans and the relationship between NDVI (Normalized Difference Vegetation Index) and productivity. Two experiments were conducted at the Universidade Estadual de Londrina (2012/2013 and 2013/2014 crops), both with experimental design of random blocks (6x4). The treatments aimed at obtaining a disease gradient (Asian soybean rust) by means of different numbers and times of application of fungicide. The quantification of the severity of the disease was made through the diagram scale and the readings of NDVI. Were analyzed the total mass, the 1.000 grains mass, the humidity, and productivity in kg ha^-1. A decrease in productivity was observed in connection with the delay in the application of the fungicide and the same happened in the area below the NDVI curve. At the same time when a statistical difference between the treatments of the severity was observed there was also a significant statistical difference (P<0.05) between the values of NDVI. The NDVI contributes to decision making about the best moment for the application of fungicide in the culture of soy for the control of Asian rust and presents regular results for the estimation of productivity.