Row spacing, cultivar and fungicide application affect the incidence of soybean stem blight

Nédio Rodrigo Tormen,Luiz Eduardo Bassay Blum

doi:10.14393/bj-v36n5a2020-42123

Abstract

Brazil is a major soybean production country and cultivate yearly more than 36 million hectares. Several factors have been reported reducing soybean production and occurrence of diseases is one of the most important. Some diseases such as the pod and stem blight (Diaporthe phaseolorum var. sojae) can limit soybean yield by shortening plant cycle and reducing seed quality. Field experiments were conducted aiming to evaluate the effect of row spacing, soybean cultivar and fungicide application on the incidence of pod and stem blight on soybean. The trial was carried out twice, with planting date at 11/15/2012 and 12/15/2012, in Planaltina-DF, Brazil. Treatments were arranged in a split-split plot scheme obeying the randomized block design. The factors evaluated were row spacing (42, 60 and 75 cm), soybean cultivars (“Syn1180RR” and “Syn1080RR”) and spray or not the fungicide Boscalid (500 g a.i./ha) at R1 and R3 soybean growth stages. Disease incidence was assessed on stems at the harvest time and on seeds after harvest and yield was estimated. Results obtained show that broader row spacing increased disease incidence on stems and seed, cultivar “Syn1180RR” was more susceptible than “Syn1080RR” and fungicide application reduced disease incidence. Pod and stem blight significantly reduced soybean yield.

Highlights

Several factors limit soybean yield in Brazil and occurrence of diseases is certainly among the most important ones
In the trial 2, there was no interaction among the factors and just the main effect of row spacing, soybean cultivar and fungicide application affected pod and stem blight (PSB) incidence
Results are presented in the interaction row spacing vs. fungicide, with soybean cultivars separated (Figure 1)

Summary

Introduction

Several factors limit soybean yield in Brazil and occurrence of diseases is certainly among the most important ones. Resistant cultivars to the major diseases are scarce and farmers have used fungicides extensively to control major foliar diseases (CRUZ et al 2014). For the stem canker (Diaporthe phaseolorum f.sp meridionalis) infection, in the disease complex, the main control method is plant resistance (HILLEN et al 2006). Occurrence and damage potential of some diseases, commonly referred as “secondary diseases”, like those caused by the Diaporthe / Phomopsis complex, have been underestimated. Where the environmental conditions are favorable, PSB has limited soybean yield (PEDERSEN; GRAU, 2010). Reports available about this disease at Brazilian conditions are scarce and farmers lack information about control practices

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Results

Conclusion