Las malezas y su control en el cultivo de la yuca en Colombia

A survey was made of weed species, weed densities and common weeding practices on 3 visits during the growing season to some 300 farms in 5 cassava-growing regions of Colombia. Broadleaf weeds were the commonest in all regions (62-65 percent of the species); there was a shift to slightly more grasses and sedges as the cassava grew older. Surprisingly, Pteridium aquilinum was the commonest weed; other serious problems were Bidens pilosa and Cyperus rotundus. Significant variations existed from one region to another; however, several of the weeds were common to many regions. Weeds with the highest populations did not coincide very closely with the most frequently encountered species. Most of the annual grasses, sedges and broadleaf weeds found are susceptible to the currently recommended herbicides, but further research is needed on several perennial grasses (P. aquilinum and Sida spp.). Nearly all weeding is performed manually; chemical control was used by only 3 percent of the farmers sampled. Av no. of weedings/crop was 3.3. Weeding accounted for 50 percent of the total labor requirements in cassava production and greater than 1/3 total costs. Farmers do not apply herbicides due to relative costs of herbicides and labor, lack of information, lack of capital, unavailability of the right type of herbicides, and limited availability of herbicides in reasonally small containers. The usefulness of an agro-economic survey to identify problems in the field is pointed out. (AS)