Determination of Density of the Amaranthus retroflexus L. in Cotton Fields of Siirt Province and Investigation of Trifluralin Resistance in Some Biotypes

Abstract

The aim of this study was to determine the distribution of pigweed (Amaranthus retroflexus L.) and trifluralinresistant biotypes of this weed in the cotton production area of the Siirt provience. The density and frequency of A. retroflexus was determined based the two seasons, May-June season reflected 0.37 plants m-2 – 32.05% and September- October season reflected 1.20 plants m-2 – 51.80%. Suspicious A. retroflexus seed samples were collected from 11 different cotton fields for determination of resistance in 2008. First, a rapid petri dish seed bioassay test was applied to A. retroflexus seeds in order to find the proportions of resistant (R) and susceptible (S) populations. The experiment was arranged as a randomized complete block design with four replications. The seeds were treated with trifluralin at 10 ml which corresponds to 200 ml da-1 the recommended dosage to treat the fields and put into a growing chamber at 25 oC for ten days. Three populations were found as susceptible and the dose ranges of trifluralin which applied to these populations were 0, 50, 100, 200, 400, 800, 1600, and 3200 ml da-1. The data obtained from these experiments was analyzed by using the logistic dose response model and 2 populations resistant or susceptible were determined.

Keywords

• Amaranthus retroflexus
• cotton
• trifluralin
• resistance
• pigweed