African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 5765

Full Length Research Paper

Estimated damage caused by ramularia leaf spots on cotton

Thiago Alexandre Santana Gilio
  • Thiago Alexandre Santana Gilio
  • Universidade Estadual de Maringá (UEM), Maringá, Paraná, Brazil.
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Dejania Vieira de Araujo
  • Dejania Vieira de Araujo
  • Universidade do Estado de Mato Grosso (UNEMAT), Tangará da Serra, Mato Grosso State, Brazil.
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Kelly Lana Araujo
  • Kelly Lana Araujo
  • Universidade do Estado de Mato Grosso (UNEMAT), Cáceres, Mato Grosso State, Brazil.
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Thomas Edson Fregonese
  • Thomas Edson Fregonese
  • Universidade do Estado de Mato Grosso (UNEMAT), Tangará da Serra, Mato Grosso State, Brazil.
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Rodrigo Chimenez Franzon
  • Rodrigo Chimenez Franzon
  • Universidade Estadual de Maringá (UEM), Maringá, Paraná, Brazil.
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Jaqueline Aguila Pizzato
  • Jaqueline Aguila Pizzato
  • Universidade do Estado de Mato Grosso (UNEMAT), Tangará da Serra, Mato Grosso State, Brazil.
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  •  Received: 19 September 2016
  •  Accepted: 14 December 2016
  •  Published: 05 January 2017

Abstract

The objectives of this study are to establish damage functions for the Ramularia areola pathosystem and characterize the damage in cultivars susceptible and resistant to it. The experiment was conducted in the city of Tangará da Serra in the 2012/2013 harvest season. The experimental design was randomized blocks with four replications in a factorial arrangement of four cultivars × four gradients. The plots were divided into two subplots (twin plots). The division I received fungicide applications at intervals of 15, 30 and 45 days and no applications to establish the gradients of the disease, and the division II received weekly applications of fungicide in order to be kept without the disease or at minimum levels. FiberMax 993, FMT 701, FMT 707 RX and IAC 25 RMD cultivars were used with different reactions to ramularia spots. Disease severity was weekly determined and used to calculate the area below the disease progress curve (ABDPC). In addition to area below the severity progress curve (ABSPC), the variables related to the following production components were obtained: seed cotton productivity, damage, percentage of damage to productivity, average number of bolls per plant, weight of one hundred seeds, percentage of fiber, and components related to fiber technological characteristics. Analyses of variance were conducted and data were adjusted by the linear integral model. The ABSPC variable showed a high relation with damage and percentage of damage to productivity. Estimates reached levels of up to 975.42 kg ha-1, or 36.83%, of damage to productivity.

 

Key words: Damage, functions, Ramularia areola, Gossypium hirsutum, fiber technological characteristics (HVI).