Population fluctuation and dispersal of the banana weevil Cosmopolites sordidus (Germar)

Abstract

In order to know what happens in a plantain plantation attac­k, ed by Cosmopolites sordidus (Germar) when it is renewed by planting a healthy seed, and also what is the influence of de soil humidity and the oversaturation (water excess) in the soil on the number of the captured adult in two kinds of baits or traps, this work was realized in the "Naranjal" farm, in Chinchiná in a plan­tation of 288 plants of the variety Dominico-hartón. For every 18 plants two traps were used, one'made of rhi­zome and the other of pseu­dostem. The traps were placed or trap months after the re­planting and were changed every four weeks. A total of 53 weekly observations were made. The meteorological data were registered in a sta­tion nearby. In order to mea­sure the dispersión of the pest, an evaluation of the population was the destruction of the plantation and a second one 15 months after the replant. On the other hand, some of the captured adults were marked and release- within the traps and on the borders of the plantation. Some of the marked specimens were recaptured af­ter two weeks at 6 to 8 meters of dis­tance; a small number of those released within the traps were observed af­ter two days. Twenty-three months after recording the pest in the plan­tation, no specimen was found in ano­ther plantation 20 meters apart. The insect is not attracted by the descom­position of the material used for the traps. The traps made of rhi­zome were preferred by C. sordidus adults over those made from pseudostem. The accumulated weekly rainfall, as well as the rainfall, occurred 24 hours before the observations, did not have any relation with the number of captured adults. The over-saturation calculated in the base of the weekly rainfall and evaporation before the observation neither had a relation with the population observed each weed. The plantain black weevil is dispersed in the seed transported by the man, and it is an insect with subterranean habits that are not affected by the environmental conditions.