Tesis Maestría en Ciencias en Recursos Naturales y Desarrollo Rural El Colegio de la Frontera Sur 2000

Bibliografía: hojas 14-16

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The "chacuatete" Idiarthron subquadratum (Orthoptera: Tettigoniidae) is a sporadic pest of coftee in parts of Mesoamerica. Information is particularly sparse of the ecology, behavior and pest status of this insect. Mark-recapture techniques were employed to determine the adult population size in coffee plantations in the municipality of Siltepec, Chiapas, Mexico where the insect has caused crop losses of around 50% over the past decade. Eight experimental blocks 50 x 50 m were defined in an area of 2,500 m2. Half of the experimental blocks contained banana plants and half of the experimental blocks did not. A trap was designed consisting of a bamboo tube 30 cm in length and closed at one end. Trials indicated that insect trapping efficiency was not improved by the presence of baits. Traps placed above the ground in coffee bushes or as banana leaves placed on the side of an experimental gauze cage captured significantly more I. subquadratum individuals than traps placed on the ground. Tests with different types of paint combinations revealed that nitrocellulose paint was durable, water-resistant and non-toxic to I. subquadratum. Mark-recapture experiments were performed at 48 h intervals over the period of 1 month. In parallel, direct nocturnal observations of I. subquadratum individuals feeding on coffee leaves and berries were made on four occasions during the study period. The prevalence of I. subquadratum feeding damage was also quantified at three sample dates during the study. Mark-recapture data were pooled for blocks with and without banana due to a low prevalence of recaptures. Most of the models tested gave statistically similar mean population estimates (±S.E.) ranging from 1167±293 for Jackson's negative index, 1300±326 for Jackson's positive index, 1880±578 for Fisher-Ford, 2006±361 for the Lincoln-Petersen index and 2759±601 for Jolly-Seber's stochastic model. All of these models were also statistically similar to estimates generated by direct nocturnal counts of insects observed feeding on coffee bushes. In contrast, Bailey's triple capture model gave a population estimate of 502±226, significantly lower than the other models (F=4.82, d.f.=6,42, P<0.008). I. subquadratum feeding damage to coffee berries varied between 15 and 45% and was significantly greater in blocks interplanted with banana. We conclude that mark-recapture methods combined with analysis using the Lincoln-Petersen model are simpler and less time consuming than direct nocturnal observations but give quantitatively similar population estimates. Personal safety of the experimenter during nocturnal insect counts was also an issue of relevance in this study. Inglés

Entomología Tropical