Ecologia do bicudo-do-algodoeiro Anthonomus grandis Boheman, 1843 (Coleoptera:Curculionidae) no Cerrado do Brasil Central

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The boll weevil Anthonomus grandis Boheman, 1843 (Coleoptera: Curculionidae), one of the main pests of cotton, was introduced in Brazil in 1983. It causes the most serious damage to the crop, such as the falling of the flower buds, destruction of bolls and reduced linter production. The serious pest status of the boll weevil is mainly due to its high reproductive capacity, highly efficient rate of colonization and spread, serious damage caused to commercially valued plant parts, and low efficiency of natural biological control agents in regulating boll weevil population. Furthermore, the endophagous feeding habit of larvae protect them from insecticidal sprays and only adults are affected by chemical control tactics. A better understanding of the biology and ecology of this insect could help in the development of more effective control strategies. The objectives of this work were: (1) to describe the patterns of boll weevil movement from cotton fields to neighboring natural areas (Cerrado and Gallery Forest), the distribution and abundance of the boll weevil inside cotton fields, and the possible locations used as refuge outside cotton fields; (2) to investigate the boll weevil feeding behavior by identifying the plant species fed by adult boll weevil outside the cotton fields through the analysis of the pollen grains found in the insects digestive system; and (3) to study the patterns and dynamics of the boll weevil infestation. The study was conducted in two experimental sites. The first site consisted of two cotton fields and two areas of natural vegetation bordering the fields, one covered by Cerrado vegetation and the other one by a Gallery Forest. Pheromone traps were placed in each experimental area, distributed in a grid consisting of four transects and five lines of traps. The lines represented the distance from the cotton fields and were distant 70m from each other. The pheromone traps were placed one meter above the ground in the intersections between transects and lines. Adults collected in the traps throughout the year were submitted to an acetolyse process for the identification of the pollen grains ingested by the insects. The second study consisted of eight experimental plots, four treated with chemical insecticides and four controls (not treated). Samples were collected every week throughout the cropping season by walking in zigzag inside each plot, collecting flower buds and bolls from the above one third of five plants and from the soil immediately bellow each plant. The results showed that the boll weevil migrated from the Cerrado to the cotton field with no defined pattern of colonization from the borders to the center of the field. Movement of the boll weevil from the Gallery Forest to the cotton field was not observed. The movement from the cotton fields to the natural vegetation areas was predominantly observed just after harvesting. In the cotton field close to the Cerrado the insect abundance was higher in the center, and in the field close to the Gallery Forest abundance was higher in the border. Insects were captured in the Cerrado during the whole year. The classification of the pollen grains ingested by the insects showed that the boll weevil fed on 19 different plant families during and between cropping seasons. The Smilacaceae family was the most frequently used as food resource, followed by the families Proteaceae, Melastomataceae-Combretaceae and Myrtaceae. This is the first record of Smilacaceae as food plant of the boll weevil. Furthermore, the results show that this pest has the capacity to colonize and cause damage above control level early in new areas cropped with cotton for the first time. During the fallow period in the dry season in the Cerrado, part of the adult population does not leave the old bolls and stay in the area, possibly as a survival strategy.

ASSUNTO(S)

flutuação populacional bicudo-do-algodoeiro ecologia dispersão

ACESSO AO ARTIGO

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