Alternative products isolated and associated with fungicide at different sowing times to control soybean powdery mildew

Abstract

Soybean (Glycine max) is the most important legume cultivated in the world. With the aim of studying alternative products isolated and associated with fungicide on the efficiency of controlling powdery mildew (Microsphaera diffusa), in two sowing seasons, field experiments were conducted in Ponta Grossa, PR, Brazil, during the 2016/2017 and 2017/2018 seasons. The treatments were: 1- control (water), 2- Bacillus subtilis lineage QST, 3- Bacillus subtilis lineage QST associated with fungicide, 4- 1% chitosan, 5- 1% chitosan associated with fungicide, 6- sulfur, 7- sulfur associated with fungicide, 8- sodium hypochlorite, 9- sodium hypochlorite associated with fungicide, 10- fungicide (2 applications) and 11- fungicide (3 apllications). In all fungicide treatments, azoxystrobin + benzovindiflupyr with adjuvant was used. The variables evaluated were: powdery mildew severity and yield. The severity data made it possible to calculate the area under the disease progress curve (AUDPC). AUDPC values were higher in the second sowing season. Sulfur, chitosan and B. subtilis, isolated, reduced AUDPC, but when associated with the fungicide they obtained superior results. Sulfur, whether or not associated with the fungicide, provided less severity of the disease. The fungicide applied three times showed better control than two applications. The highest yield averages were, obtained in the first sowing season. There was no difference between the treatments during sowing in October for yield, this was affected by the treatments, only in the second sowing season, highlighting the sulfur associated with the fungicide.