Manejo de dos plagas clave para forrajes de las sabanas neotropicales.

English. Rotations and relay-cropping systems of rice and pastures have demonstrated potential for improving soil fertility, maintaining soil structure and increasing rice yields in the lowland neotropical savannas. The major components of these cropping systems, rice and forage grasses, share susceptibility to two major insect pests: species of Cercopidae known as spittlebugs, and leaf-cutter ants (Atta and Acromyrmex spp.). This article describes work on the control of these pests through cultural practices and host plant resistance. Management strategies are proposed to minimize losses. Cercopids can be controlled to a limited extent through strategic grazing although the development of resistant hybrid Brachiaria cultivars offers the greatest potential for effective control. Resistance to leaf-cutters is also present in the genus Brachiaria. Methods to assess populations of leaf-cutter colonies are described as well as damage to susceptible grass cultivars. Estimation of colony density prior to planting is recommended in order to select the proper grass cultivar.

Spanish; Castilian. Aunque los cercopidos y las hormigas arrieras son plagas importantes y con potencial en las sabanas neotropicales, el uso de variedades resistentes de gramineas forrajeras y practicas culturales pueden minimizar los danos ocasionados por estos insectos en pasturas y en los sistemas arroz-pastos. El avance en las tecnicas que permiten la recombinacion genetica entre especies de Brachiaria ofrece, por primera vez, la posibilidad de combinar caracteristicas como la resistencia a cercopidos y hormigas arrieras, y la adaptacion a suelos infertiles, previamente encontradas en genotipos distintos. El papel de estas nuevas variedades de Brachiaria sera fundamental para futuros sistemas integrados y sostenibles de cultivos y ganaderia en las sabanas de zonas bajas de America tropical.