Trichoderma Harzianum and the Management of Nursery Diseases of Theobroma Cacao and Anacardium Occidentale

Cocoa (Theobroma cacao L.) and cashew (Anacardium occidentale L.) are important export crops in the tropics, with significant contributions to the livelihood of smallholder farmers and national economy. Fungal pathogens severely constrain production in these crops and of effect were the pathogens causing disease at seedling stage. These invariably result into high mortality and poor field establishment. Dependence on synthetic fungicides for disease management has raised global concerns on risks, therefore a sustainable, eco-friendly biological alternatives is critical for crop, soil and human health. Five major pathogenic fungi; Aspergillus fumigatus, Fusarium pallidoroseum, Lasiodiplodia theobromae, Colletotrichum gloeosporioides, and Botryodiplodia theobromae were routinely cultured from diseased cocoa and cashew seedlings and characterized morphologically. The biocontrol potential of Trichoderma harzianum was evaluated against isolated pathogens in-vitro using a dual culture technique. Efficacy of T. harzianum was compared with carbendazim, and Percentage Inhibition of Radial Growth (PIRG) and Colony Interaction Index (CII) were determined. Colletotrichum gloeosporioides recorded least growth (32.7%) inhibition and highest (60.98%) inhibition of B. theobromae by T. harzianum. Carbendazim however inhibited growth of C. gloeosporioides and B. theobromae by 63.90% and 87.5% respectively. Other pathogens have shown varied degree of inhibition by T. harzianum and Carbendazim. The CII scores (1–2) indicated strong mycoparasitic and competitive interactions between T. harzianum and pathogens. Trichoderma harzianum has significantly shown its bio-efficacy as a sustainable biocontrol agent for managing the tested pathogens. Its eco-friendly mode of action and broad-spectrum efficacy support its inclusion in integrated disease management programs