Effect of Time of Spraying of Fungicide and Foliar Nutrient on Soybean Powdery Mildew

Abstract

With the objective of determining the effects of initial infection level (% leaf area infected, % l.a.i.) at the time of fungicide and foliar nutrient application for the control of powdery mildew, a study was carried out under greenhouse conditions at Embrapa Soja, Londrina, P.R. The fungicide tebuconazole (100 g a.i./ ha/application) and sulphur fungicide (2.0 kg a.i./ha/ application), sprayed at 20, 30, 40 and 50% l.a.i. (growth stages V3 and V5, between R5.1 and R5.3), and three applications (at V3, V4 and R5.1, beginning at 20% l.a.i.) of tebuconazole were compared with sulphur foliar nutrient (sulphur at the dose of 125 g a.i./ha/ application). The highly susceptible BR-16 cultivar was used in a completely randomized design with 11 treatments, five replications (pots) and five plants per pot. The parameters evaluated were: % l.a.i., % yellowing leaf when the control reached growth stage R7.2 (between 50 and 75% yellow/mature leaves), % defoliation (% defol.) when the control plants reached R8.2 (pre-harvest maturity), number of pods and seeds and seed weight (s.w.) per plant. The area under the disease progress curve (AUDPC) was determined based on disease progress. The % l.a.i. and AUDPC of the control (98% and 65.41) differed from other treatments (3.5-64.2% l.a.i. and 13.57-40.59 AUDPC). The % l.a.i. for the sulphur fungicide treatment (41.9-64.2%) and sulphur foliar nutrient (49.8%) were greater than for tebuconazole (3.5-28%). The % defol. of the control (90%) differed from tebuconazole applied at 30% initial infection (48%), with three applications (45%), and from sulphur foliar nutrient (47%). The s.w./plant of the control (2.23 g) was lower than that of tebuconazole treated at 40% IL (3.03 g) and at 20% IL (3.35 g) and for sulphur foliar nutrient (3.7 g). The initial disease severity (20-50% l.a.i.) did not affect the level of powdery mildew control and the sulphur foliar fertilizer resulted in greater number and higher s.w./plant.

Impact and Control of Powdery Mildew on Irrigated Soybean Varieties Grown in Southeast Australia

“…Microsphaera diffusa)-is an important disease of soybeans, particularly in the United States, Paraguay, Brazil and Bolivia. However, this disease has only recently been observed in Australia [1][2][3][4][5][6]. The fungus is an obligate parasite and is characterised by white-grey mycelia and conidia growth which can be observed on all above-ground plant parts [1,6].…”

“…However, this disease has only recently been observed in Australia [1][2][3][4][5][6]. The fungus is an obligate parasite and is characterised by white-grey mycelia and conidia growth which can be observed on all above-ground plant parts [1,6]. During the early disease development stages, fine off-white or white fugal growth appears on the top surface of leaves [1].…”

“…It is likely that the disease survives between seasons on legume hosts, such as volunteer soybean, field pea and other broadleaf weeds within its host range, before re-infecting crops in the following season [10]. The application of fungicides and the selection of resistant cultivars have been identified as two effective, commonly used approaches of managing powdery mildew [6].…”

Modeling the relationship between estimated foliar fungicide use and soybean yield losses due to foliar fungal diseases in the United States

“…Several studies have demonstrated no significant increase in soybean yield with fungicide applications in the absence of disease [20–23], while other studies suggested that yield increases can occur with foliar fungicide application even in the absence of disease [7, 23–25]. Therefore, the economic return following a fungicide application does not intuitively follow a linear trend due to its apparent dependency on multiple factors such as disease pressure, class of fungicide being used (i.e., active ingredient), time of application (growth stage of the plant), and environmental conditions [19, 26, 27].…”

Effects of organic fertilizer (NPK 5-9-19) and mineral (NPK 12-11-18) on soil chemical properties in tomato crop in the South and Mid-west of the Ivory Coast

“…Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License (Soro et al, 2015). Many producers make more and more use of liquid organic fertilization due to these constraints (William et al, 2004;Yorinori et al, 2004). These producers act thus, in the direction of improving the soil fertility and allowing a better availability of the soil nutrients for the plant, in order to guarantee a better productivity.…”