Interference of itchgrass in sugar cane and the indaziflam and indaziflam + metribuzin selectivity applied on pre-sprouted seedlings in sugarcane

Author(s)

Neriane Hijano

• Document type: Master's Dissertation
• Press: Jaboticabal. 2016-09-16.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2016-07-20
• Advisor: Pedro Luis da Costa Aguiar Alves

Abstract

Weed interference in sugarcane is a determinant factor to maximum crop productivity and quality, especially among these itchgrass (Rottboellia cochinchinensis), whose importance has been growing in recent years. In order to manage these weeds aiming to minimize the interference, the knowledge of their periods of interference in sugar cane crops allows better placing of residual action herbicides. This work's objective is to determine the interference period of itchgrass in sugar cane, the critical density of itchgrass that interferes on the development of pré-sprouted seedlings of sugar cane and their resprouting and the selectivity of the herbicides Indaziflam and Indaziflam + Metribuzin on pré-sprouted seedlings of sugar cane. To determine the periods of interference of itchgrass on sugar cane, the experiment was carried out in a commercial area with the CTC14 variety planted on january. The periods of cohabitation or control were 0-23, 0-37, 0-44, 0-58, 0-72, 0-92, 0-122, 0-240, 0-300, 0-450 days after planting. Given a 5% productivity reduction tolerance on the sugar cane crop with infestation of itchgrass predominantly, the period before interference found was 54 days, and the total prevention period was 130 days. There was a 26,4% reduction on productivity when the total lack of weeds and the presence of weeds during the complete cycle are compared; the total retrievable sugar value diminished with the increase of cohabitation period. To determine the densities of R. cochichinensis that interfere on the develoment of pré-sprouted seedlings and their effect on resprouting, the outline applied was randomized blocks with four replications, with Itchgrass population of 1; 2; 4; 8 and 16 plants per vase for 'RB855156' and 1; 2; 8 and 16 plants per vase for 'CTC14', and the trial white sugarcane plant in the absence of itchgrass. For the Itchgrass the treatments were composed by the various densities in presence and absence of sugarcane. At 25, 55, 85 and 120 days after planting of seedlings were analyzed, for the main stalk, the height, diameter, number of leaves and tillers. At 120 days after planting were also assessed the leaf count, leaf area and dry matter. The plants were cut at the base, keeping the lower parts of both varieties in absence of weeds for 90 days to analyze the resprouting. The growth of the itchgrass' population did not interfere on the assessed characteristics of the main stalk, but lowered the tiller count, the number of leaves and also lowered tiller leaf area and dry matter. For the 'RB855156' there was no resprouting 90 days after cut. The weed suffered intraspecific competition on the larger tested densities. The selectivity experiment was split on four parts, applying two varieties of sugar cane (RB966928 and CTC14), with the pré-sprouted seedlings method, and two herbicides (Indaziflam and Indaziflam + Metribuzin). The outline applied was completely randomized with four replications, in a 2 x 4 factorial scheme, with two applying techniques (pre and post planting) and four doses of herbicide. At 10, 25, 40, 55 and 70 days after application the fitotoxicity symptoms were visually analyzed, and the main stem was characterized for height, diameter, leaf count and tiller count. At 70 days were also analyzed the total leaf count, main and secondary stems' leaf area, dry mass of roots and aerial part. The herbicide Indaziflam was selective for the RB966928 variety when applied post planting with the lower dose, Indaziflam + Metribuzin was selective for the RB966928 variety when applied post planting with doses as high as 75+960 g i.a. ha-1. The application pre planting of both herbicides resulted on death for both varieties. (AU)

• FAPESP's process: 14/24460-3 - Periods of interference itchgrass in sugarcane and its management with herbicide indaziflam
• Grantee: Neriane Hijano
• Support Opportunities: Scholarships in Brazil - Master