Economic damage caused by spittlebugs (Homoptera: Cercopidae) in Colombia: a first approximation of impact on animal production in Brachiaria decumbens pastures

摘要

Using a simulation model as an analysis tool, the economic impact of spittlebugs in pastures of Colombia was quantified in terms of animal production. Three levels of abundance (10, 25, 50 adults/m~2) and farm area affected (25, 50, 100 percent) were evaluated using data obtained in Brazil for Notozulia entreriana (Berg) on Brachiaria decumbens Stapf. The model considered dual-purpose production systems in two contrasting ecosystems: (1) the dry tropics, characterized by a well defined, 6-month rainy season and (2) the humid tropics, characterized by uniform rainfall distribution throughout the year. Compared to healthy pastures, stocking rate, milk and meat productivity decreased 1-8, 8-34 and 38-54 percent, respectively, at low, intermediate andhigh abundance levels, depending on farm area infested. The cost of producing milk and meat increased 0-4,3-16 and 18-30 percent at the same infestation levels, causing net income to decrease 3-16, 17-69 and 67-100 percent. At the regional level, economic damage in the 1,140,000 ha sown to grasses susceptible to spittlebugs in the humid tropics of Colombia ranged from US7-25, 28-36 and 39-47 million dollar/yr. In the 4,720,000 ha of susceptible grasses in the dry tropics, economic damage was US33-118,132-175 and 228-273 million dollar/yr. The investment required to develop grass varieties resistant to spittlebugs and adapted to soils with low to intermediate fertility (US6 million dollar over 12 yr) is low compared with the economic damage caused byspittlebugs in Colombia, and therefore presents a major economic incentive for support of research on varietal improvement and spittlebug management.