Tuesday, September 11, 2007

Comparison of Densities of insect pest and predators in the cotton crops in no tillage, two row distances, and with or without irrigation

Mrs. Maria Ana Sosa1, Mrs. Daniela E. Vitti Scarel1, and Mrs. Silvia M. Mazza2. (1) INTA EEA RECONQUISTA, CASILLA DE CORREO 1, RECONQUISTA (SANTA FE), 3560, Argentina, (2) Universidad Nacional del Nordeste., Departamento de Matemática y Estadística. Facultad de Ciencias Agrarias., Sargento Cabral 2131, Corrientes, 3400, Argentina

Alabama argillacea Hübner (Lepidoptera: Noctuidae) (ALA), and Horcias nobilellus Berg (Hemiptera: Miridae) (NH) damage cotton crops. The objective of this work was to compare densities of population of pest and predators in cotton crop under no tillage, two row distance (0.45 and 0.90 m), with and without irrigation. A three-year study was conducting in Reconquista (Argentina) with plots at random with three replications. Vertical cloth (0.5 m) was used for sampling insect, twice by plot, nine observations by year. The variables are: number by 0.90 m-2 of ALA, HN, predators (PRE), coccinellidae (COC), predator Hemiptera (HEMP); spiders (SPID).  Variance Multivariate Analysis (MANOVA) and Hotelling test (α=0.05) was used. The MANOVA (Wilks) detected significant differences between years (p<0.0001), irrigations (p=0.0406) and distances (p<0.0001). ALA and HN and SPID and COC registered differences between years, 2004 > 2003 > 2005. Irrigated plots have more HN, PRE, SPID and COC. When shortening the distance between rows the number of ALA, HN and PRE by surface increased, but it did not vary for COC, HEMP and SPID.

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