Abstract

Groundnut (Arachis hypogaea L.) is an important cash crop in the lowland areas of Ethiopia. However, prevalence of Aspergillus invasions and subsequent aflatoxin contamination compromises the quality of groundnut kernels. This study was conducted to evaluate the effect of farm yard manure (FYM) and seed treatments against Aspergillus species pod colonization and aflatoxin accumulation under field conditions. The inhibitory efficacy of Trichoderma species as biocontrol agents was also assessed. A total of 20 treatment combinations including pre-planting applications of FYM at 0, 2.5, 5, and 7.5 tons/ha and seed treatments with carbendazim at 2 g/kg and mancozeb at 3 g kg^-1, and Trichoderma harzianum and Trichoderma viride each at 5 g/kg as well as untreated seed as control were used. Treatments were laid out in a randomized complete block design (RCBD) in three replications. The experiment was conducted in two consecutive seasons (2014 and 2015) at Babile Haramaya University sub-Research Station. The highest pod and seed yields (1901.5 and 1281.5 kg/ha, respectively) were recovered from plots treated with T. harzianum at 5 g/kg seed. A. flavus was abundantly recorded in control plots, which could be responsible for the high aflatoxin B₁ (5704.4 µg/kg) and B₂ (2219.0 µg/kg) contamination. However, plots treated with T. harzianum at 5 g/kg seed and FYM at 5 tons/ha + T. harzianum at 5 g/kg were free from aflatoxin. Integrations of T. harzianum as biocontrol seed treatment and soil amendment with FYM were effective in the pre-harvest management of Aspergillus spp. and aflatoxins contamination.

Key words: Aflatoxin, Aspergillus, carbendazim, farm yard manure, groundnut, mancozeb, Trichoderma species.