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

Abstract

-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. Relação entre ocorrência da bicheira-da-raiz e profundidade da água em arroz irrigado por inundaçãoResumo -O objetivo deste trabalho foi determinar a relação entre profundidade da água de irrigação e infestação larval de Oryzophagus oryzae em arroz irrigado por inundação. A profundidade da água e a infestação larval foram avaliadas no leiveiro superior, no centro do quadro e no leiveiro inferior. Os dados foram submetidos às análises estatística descritiva e geoestatística. A maior infestação larval ocorre em áreas da lavoura de maior profundidade da água, típica do leiveiro inferior. A distribuição espacial das larvas de O. oryzae é do tipo agregada e dependente da maior profundidade da lâmina de irrigação.Termos para indexação: Oryza sativa, Oryzophagus oryzae, geoestatística, distribuição espacial.

Morphoanatomical and biochemical factors associated with rice resistance to the South American rice water weevil, Oryzophagus oryzae (Coleoptera: Curculionidae)

“…Seedlings produced in a greenhouse were transplanted into plots 20 days after emergence, in October. Three days after transplanting seedlings, the flood was gradually increased to a depth of approximately 15 cm, which is the preferred condition for the natural infestation of O. oryzae 63 . The plots were kept flooded until they were drained for harvest.…”

Differential response to the South American rice water weevil (Coleoptera: Curculionidae) damage of rice cultivars with contrasting levels of resistance: implications for field management

“…2(A)] until it stabilized at 15 cm, a depth favorable for the RWW. 38 The plants in the cages did not receive fertilizer or insecticide and herbicide applications. The fungicide tricyclazole [Bim® PM, 75.0% ai (active ingredient); Dow AgroSciences Industrial Ltda, São Paulo, Brazil ] was applied at 0.3 kg ha −1 between R 1 and R 2 rice stages, and trifloxystrobin+tebuconazole (Nativo® SC, 10.0 + 20.0% ai; Bayer SA, São Paulo, Brazil) was applied at 0.7 L ha −1 at R 4 rice stage 39 (rice phenological stages according to the Counce et al 36 scale).…”

Spatial Dependence Index for Cubic, Pentaspherical and Wave Semivariogram Models

“…The SDI has the potential to evaluate spatial dependence from the semivariograms adjustment, which may be the only index used for such evaluation (Pazini et al, 2015;Buttow et al, 2017;Pelissari et al, 2017), or be used in conjunction with other measures of spatial dependence (Oldoni, Bassoi, 2016).…”

“…Spatial dependence measures are useful to make classifications and comparisons among different spatial dependence scenarios (different spatial phenomena) (Biondi et al, 1994) without the necessity to take the whole semivariogram. In addition, as an index, they can be used to evaluate the quality of model fit to the semivariogram (Ávila, et al, 2010;Pazini, et al, 2015;Oldoni, Bassoi, 2016;Buttow et al, 2017) and, in consequence, to indicate whether the kriging interpolation will result in good quality maps. Even though the Cubic, Pentaspherical and Wave models have potential applicability in the Environmental Sciences, Geosciences, Soil Sciences and others, there is not a spatial dependence index that considers their specifications.…”