Population dynamics and spatial distribution of Spartocera dentiventris (Berg) (Hemiptera: Coreidae) adults on nicotiana tabacum L. (Solanaceae)

Abstract

Spartocera dentiventris (Berg), the gray-tobacco-bug, feeds on the sap of the plant, inducing leaf wilting and twisting, thus causing economic losses to the tobacco crop. The knowledge on its population dynamics is crucial for the development of efficient techniques for monitoring and managing this species. An experimental tobacco (Nicotiana tabacum) crop was established in Porto Alegre County, South Brazil, aiming to study the colonization, establishment, growth and spatial distribution of the adult S. dentiventris population using the mark-release-recapture method. All plants were inspected at least three times a week. From August 1999 to April 2000, 217 individuals were marked. Only one generation completed development up to the adult phase. Population size estimated by the Fisher-Ford method peaked at ca. 160 individuals. Average recruitment was 5.0 ± 2.67 females per day and 6.6 ± 1.73 males per day (z = 0.71; df = 118; P = 0.477). Most individuals concentrated in the upper part of the plant and on the abaxial face of leaves. Analysis performed in groups of six plants revealed an aggregated pattern of distribution in 78.4% of sampling occasions. Individuals concentrated in certain areas of the crop and the population size seemed to be highly susceptible to weather variations and predation. These observations should be taken into account on designing measures for monitoring and control of the species.