Effects of water and nutrient on the growth of Digitaria nuda obtained from areas without reported herbicide resistance

Abstract

The occurrence of control failure after herbicide application suggests the emergence of tolerant D. nuda in sugarcane crops. However, the presence of species within the herbicide-resistant weed community before the selection process can be partially attributed to ecological adaptability. Biological studies of Digitaria spp. in areas without resistance reports are essential to understand the initial characteristics of populations before resistance events. In the present study, the predominance of Digitaria species was evaluated in ten areas of sugarcane cultivation without records of populations resistant to photosystem II-inhibiting herbicides belonging to four mills. First, we determined the sensitivity of Digitaria populations to herbicides. In addition, interspecific competitiveness and growth under nutrient and water availability conditions were determined for each identified species of Digitaria. The survey revealed a predominance of D. horizontalis and D. nuda in populations composed of D. bicornis and D. ciliaris, and all them were susceptible to herbicides. The combinations of competition between species showed no significant differences. D. nuda has a greater increase of aboveground biomass under water availability, which may favor its adaptation in areas with sugarcane straw left on the soil. The predominance of susceptible D. nuda in some populations is primarily due to its biological characteristics and its adaptation to cultivation practices. However, D. nuda plants obtained from the two susceptible populations showed differential responses to diuron, indicating diversity in populations in terms of herbicide response.