Frequency and distribution of Antestiopsis orbitalis Westwood (Hem., Pentatomidae) in coffee plantations in Burundi: implications for sampling techniques
1998
Cilas, Christian | Bouyjou, Bernard | Decazy, Bernard
The bug, #Antestiopsis orbitalis# Westwood (Hem., Pentatomidae), causes major damage in Burundi coffee plantations. Efficient management against this insect needs to have a reliable sampling procedure to estimate, with good precision, the level of the populations in coffee fields. Studies of the distribution and spatial dispersal of this bug are therefore required. To this purpose, an inventory of #A. orbitalis# in eight plots, of around 100 coffee trees each, was undertaken. The number of bugs per tree fitted well to a negative binomial law, suggesting an aggregative behaviour of this insect. However, the aggregative coefficient was not constant on the different plots and adults were distributed in a more aggregative way than larvae. Study of the spatial dispersal of this bug generally indicated no particular structure (focus or gradient); only adults tended to be distributed according to gradients. Confidence intervals on the average number of bugs per tree were calculated following the robust method of bootstrap using different sized samples. Recommendations concerning sampling procedures are proposed. (Résumé d'auteur)
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