Uso de isolados de alternaria spp. para o controle biológico do caruru amaranthus hybridus e A. retroflexus

Abstract

Weeds are among the primary factors limiting agricultural productivity, as they compete with crops for water, light, nutrients, and space. Among the most significant species are Amaranthus hybridus and Amaranthus retroflexus, which are widely distributed in agricultural areas and are recognized for their high infestation potential and competitiveness. Management of these species relies primarily on the application of chemical herbicides. However, the continuous use of these products has led to the selection of herbicide-resistant weed populations and raised concerns regarding environmental impacts, highlighting the need for more sustainable alternatives. In this context, this study aimed to evaluate the potential of different Alternaria spp. isolates for the biological control of A. hybridus and A. retroflexus. The experiment was conducted at the Microbiology and Phytopathology Laboratory of the Federal University of Uberlândia, Monte Carmelo Campus. Four Alternaria spp. isolates (BANI001, BA031, BANI032, and BANI045) were individually applied to post-emergence plants of the target species. Evaluations were conducted seven days after inoculation by observing symptoms of chlorosis, necrosis, and plant mortality, as well as by quantifying the plant population before and after treatment. The percentage of weed control was estimated using the rating scale established by the Brazilian Society of Weed Science, accounting for both symptom severity and population reduction. Results indicated differences in the aggressiveness of the isolates toward the target species. Isolate BANI001 achieved the highest level of control (52%) and was classified as providing moderate control. Isolate BANI045 provided 43% control of A. hybridus, also categorized as moderate. In contrast, isolate BANI032 achieved 15% control of A. retroflexus, while BA031 reached 25%; both were classified as providing low or ineffective control. It is concluded that Alternaria spp. isolates show potential for the biological control of A. hybridus and A. retroflexus, with BANI001 and BANI045 standing out for providing moderate control under the evaluated conditions. These findings underscore the potential for further studies aimed at developing sustainable weed management strategies.