Relationship between the occurrence of the rice water weevil and water depth in flooded rice crop

The objective of this work was to assess the relationship between the depth of irrigation water and larval infestation by Oryzophagus oryzae in flooded rice crop. Water depth and larval infestation were evaluated in the upper levee, in between levees, and in the lower levee. The data were subjected to the descriptive statistical and geostatistical analyses. The highest larval infestation occurs in field areas with greater water depth, which is typical of the lower levee. The spatial distribution of O. oryzae larvae is of the aggregate type and depends on the greater irrigation water depth.

Index terms:
Oryza sativa; Oryzophagus oryzae; geostatistics; spatial distribution.

Authorship

Germano Tessmer Büttow

Universidade Federal de Pelotas, Departamento de Fitossanidade, Avenida Eliseu Maciel, s/no, Campus Universitário Capão do Leão, CEP 96010-900 Pelotas, RS, Brazil. E-mail: germanotbuttow@hotmail.com, julianopazzini@hotmail.com, adgrutzm@ufpel.edu.brUniversidade Federal de PelotasBrazilPelotas, RS, BrazilUniversidade Federal de Pelotas, Departamento de Fitossanidade, Avenida Eliseu Maciel, s/no, Campus Universitário Capão do Leão, CEP 96010-900 Pelotas, RS, Brazil. E-mail: germanotbuttow@hotmail.com, julianopazzini@hotmail.com, adgrutzm@ufpel.edu.br

Juliano de Bastos Pazini

Enio Júnior Seidel

Universidade Federal de Santa Maria, Departamento de Estatística, Avenida Roraima, no 1.000, Cidade Universitária, Camobi, CEP 97105-900 Santa Maria, RS, Brazil. E-mail: enioseidel@gmail.comUniversidade Federal de Santa MariaBrazilSanta Maria, RS, BrazilUniversidade Federal de Santa Maria, Departamento de Estatística, Avenida Roraima, no 1.000, Cidade Universitária, Camobi, CEP 97105-900 Santa Maria, RS, Brazil. E-mail: enioseidel@gmail.com

Fernando Felisberto da Silva

Universidade Federal do Pampa, Rua Luiz Joaquim de Sá Britto, s/no, Promorar, CEP 97650-000 Itaqui, RS, Brazil. E-mail: fernandosilva@unipampa.edu.brUniversidade Federal do PampaBrazilItaqui, RS, BrazilUniversidade Federal do Pampa, Rua Luiz Joaquim de Sá Britto, s/no, Promorar, CEP 97650-000 Itaqui, RS, Brazil. E-mail: fernandosilva@unipampa.edu.br

Anderson Dionei Grützmacher

José Francisco da Silva Martins

Embrapa Clima Temperado, Rodovia BR-392, Km 78, 9º Distrito, Monte Bonito, Caixa Postal 403, CEP 96010-971 Pelotas, RS, Brazil. E-mail: jose.martins@embrapa.brEmbrapa Clima TemperadoBrazilPelotas, RS, BrazilEmbrapa Clima Temperado, Rodovia BR-392, Km 78, 9º Distrito, Monte Bonito, Caixa Postal 403, CEP 96010-971 Pelotas, RS, Brazil. E-mail: jose.martins@embrapa.br

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Figures | Tables

Figures (1)
Tables (1)

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Figure 1.
Semivariograms and prediction maps of Oryzophagus oryzae larval population in flooded rice (Oryza sativa) crop, in the sampling sites: upper levee (UL), by the Gaussian model; center of the area limited by both levees (CA), by the exponential model; and lower levee (LL), by the Gaussian model.

Thumbnail

Table 1.
Descriptive statistics for irrigation water depth (cm) and number of Oryzophagus oryza e larvae, as well as geostatistical parameters for the semivariogram models on the larval population in the upper levee (UL), center of the area between both levees (CA), and lower levee (LL) in flooded rice (Oryza sativa) crop⁽¹⁾.

Figure 1. Semivariograms and prediction maps of Oryzophagus oryzae larval population in flooded rice (Oryza sativa) crop, in the sampling sites: upper levee (UL), by the Gaussian model; center of the area limited by both levees (CA), by the exponential model; and lower levee (LL), by the Gaussian model.

Table 1. Descriptive statistics for irrigation water depth (cm) and number of Oryzophagus oryza e larvae, as well as geostatistical parameters for the semivariogram models on the larval population in the upper levee (UL), center of the area between both levees (CA), and lower levee (LL) in flooded rice (Oryza sativa) crop⁽¹⁾.

Sampling site	Variable	Minimum value	Maximum value	Mean	Standard deviation	CV (%)	I	Model	Nugget effect	Sill	Range (m)	MD (m)	SDI (%)
UL	Water depth	3.00	19.00	8.87	3.64	41.01	-	Gaussian	4.61	3,090.88	8,951.51	162.67	50.32
UL	No. of larvae	0.00	11.00	3.49	2.51	71.87	1.81	Gaussian	4.61	3,090.88	8,951.51	162.67	50.32
CA	Water depth	1.00	15.00	5.96	2.61	43.84	-	Exponential	0.63	1.28	65.17	162.67	12.90
CA	No. of larvae	0.00	6.00	1.46	1.40	96.40	1.34	Exponential	0.63	1.28	65.17	162.67	12.90
LL	Water depth	6.00	20.00	13.96	3.28	23.49	-	Gaussian	9.65	5,120.05	9,337.13	180.74	50.31
LL	No. of larvae	1.00	16.00	6.62	3.26	49.29	1.61	Gaussian	9.65	5,120.05	9,337.13	180.74	50.31

⁽¹⁾CV, coefficient of variation; I, variance/mean ratio; MD, maximum distance between points in the area; and SDI, spatial dependence index, ranging in the interval 0%≤ SDI ≤50.40% in the Gaussian model and 0%≤ SDI ≤31.70% in the exponential one (Seidel & Oliveira, 2014SEIDEL, E.J.; OLIVEIRA, M.S. de. Novo índice geoestatístico para a mensuração da dependência espacial. Revista Brasileira de Ciência do Solo, v.38, p.699-705, 2014. DOI: 10.1590/S0100-06832014000300002.
https://doi.org/10.1590/S0100-0683201400... ). Number of samples per site was 79.

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Relationship between the occurrence of the rice water weevil and water depth in flooded rice crop

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[TFN1] ⁽¹⁾CV, coefficient of variation; I, variance/mean ratio; MD, maximum distance between points in the area; and SDI, spatial dependence index, ranging in the interval 0%≤ SDI ≤50.40% in the Gaussian model and 0%≤ SDI ≤31.70% in the exponential one (Seidel & Oliveira, 2014SEIDEL, E.J.; OLIVEIRA, M.S. de. Novo índice geoestatístico para a mensuração da dependência espacial. Revista Brasileira de Ciência do Solo, v.38, p.699-705, 2014. DOI: 10.1590/S0100-06832014000300002.
https://doi.org/10.1590/S0100-0683201400... ). Number of samples per site was 79.