Durante la decada pasada, varias enfermedades de plantas forrajeras tropicales ocasionan perdidas considerables en America del Sur. Casi todas lasenfermedades han ocurrido en praderas de leguminosas nativas promisorias, en regiones de produccion de pastos, mientras que las gramineas introducidas de Africa han tenido pocos problemas de enfermedades. El significado de esta diferencia es discutible. El posible manejo de enfermedades en praderas tropicales incluye control quimico y biologico, control natural a traves de saneamiento, asociacion estrategica, manejo de praderas y resistencia.

The management of cassava intercropping and its evaluation are described. Multiple cropping systems are defined: consecutive cropping and intercropping (mixed intercropping, row intercropping, strip intercropping, and relay intercropping). Basic biological and nutritional aspects of multiple cropping are analyzed and cassava intercropping systems practiced throughout the world (Latin America, Africa, and Asia) are described.

Due to the increasing extension of areas planted to cassava in tropical countries, the maintenance of biological equilibrium through adequate integrated control techniques becomes imperative as well as the collection of data on var. resistance, biological control, and cultural practices. Basic information for integrated pest control is given. Arthropods attacking cassava are described regarding yield losses, biology, morphology, and ecology. Criteria for the establishment of a control program on var.

A guideline for carrying out regional trials in cassava is given, including necessary steps (identification of collaborators, selection of sites, identification of person in charge, planting and harvesting season, exptl. design, plot size, and border rows); the technology used (selection and treatment of cuttings, plant density, land preparation, planting position, application of herbicides and fertilizers, pest and disease control); necessary visits (a min. of 7); and final agronomic trials to determine optimum density and age of var. at harvest.

In May 1980 the soil section of CIAT's cassava program established a fertilization trial with 3 cassava var. [Barranquena (regional), M Col 113, and CMC 921 to measure its effect on yield and establish optimum levels from an economical point of view. The trial took place in Mondomito and Agua Blanca, municipality of Santander de Quilichao, Cauca (Colombia). Twelve levels of NPK (0-0- 0; 0-100-100; 50-100-100; 100-100-100; 200-100-100; 100-0-100; 100- 50-100; 100-200-100; 100-100-0; 100-100-50; 100-100-200; 200-200- 200) were applied. Partial budgeting was used for the economic analysis.