Format: ORAL

Noro F. H. Randrianarimanana1,2,Nantenaina H. Rakotomalala1,Jean-Augustin Randriamampianina4,Mijoro Rakotoarinivo2, Helene Ralimanana1, Lorna MacKinnon3,Rafael F. de Almeida3,Philippa Ryan3,Maria S. Vorontsova3

1 Royal Botanic Gardens Kew, Antananarivo, Madagascar 2 Biology and Plant Ecology Mention, University of Antananarivo, Madagascar 3 Royal Botanic Gardens Kew, Richmond, United Kingdom 4 National Center for Applied Research on Rural Development (FOFIFA), Antananarivo, Madagascar

Plants and agricultural practices are an integral part of human food systems and well-being. In Madagascar, agricultural products are both self-consumed but also constitute the local economy basis. Beside climate change, weeds are one of the main problems that hinder production, and most of them are grasses belonging to the Poaceae family. Conversely, some Poaceae considered bad for crops are used for food, medicine, and ornamentation purposes. Digitaria species, commonly known as finger grasses, are typically found in Malagasy crop fields, interacting with cultivation. This work aims to identify the best-known Poaceae weeds and understand their roles in agricultural systems. To increase our understanding of the relationship between these plants and farming activities, information on their recognition and the farmers perception of the Poaceae weed status in cropping systems was analysed. Our approach was based on field surveys and farmer interviews with plant voucher specimens and photographs in three areas of Madagascar central highlands. Additionally, we present detailed data on Digitaria species. 51 Poaceae, including 11 Digitaria species were mentioned. Farmers classify Poaceae weeds in three ways: their impacts on agricultural activities, use category, and vegetative growth patterns, the latter especially significant for Digitaria. Locally common grasses are perceived as weeds when they are abundant and cause yield loss. Overall, 67% of the species mentioned are judged useful. More than 40% of the farmers use Poaceae weeds in composting, more than 20% as fodder, and more than 8% as medicine. The diversity of useful species and the associated indigenous knowledge is important to the local communities, but weeds are still perceived as overall negative. The Poaceae are overall neglected in Malagasy ethnobotany. The data obtained will be useful for weed control as well as the conservation of agrobiodiversity, especially endemic species that are not widely known.