In tropical pastures, weeds are a significant threat and their control is an important issue depending in their ecological and economic impacts. Weed management requires information on their identification, their biology, their behavior at different scales (from field to region). Part of this knowledge is present in the stakeholder's heads (farmers, extension people, researchers, trainers), but its compilation and its diffusion present constraints of a regulatory, human and technological order. Management of information is now facilitated by digital infrastructures, but requires knowledge to be shared, updated, and disseminated. The WIKTROP collaborative portal (http://portal.wiktrop.org) allows all users in the tropical agricultural world, including grazing land, to share, capitalize and disseminate their knowledge and questioning about tropical weeds and their management for more than 700 species. The portal includes also a species identification tool and an observtion module. This bilingual (English/French) tool is available to multisystem applications (PC on- and offline, mobile for Android and iOS). Plants that appear spontaneously in pastures can be native or exotic, can be harmful or/and beneficial depending on the point of view (agricultural, medicinal, food...) and its abundance. How much information can or should be disseminated to help farmers manage weeds as best as possible? Is it necessary to eradicate or reduce the population of a particular species? Is it important that farmers take their decision with as much knowledge as possible about the disadvantages and benefits of each species? That is why WIKTROP is based on a free access to information. Sharing data, information or knowledge for the benefit of all is still poorly perceived but is fortunately developing rapidly, even in research. This becomes a recommendation or even an obligation in many national and international calls for projects and is becoming a new strategic issue. Wiktrop contributes