Abstract
ABSTRACT: The insects of the family Bruchidae (Coleoptera) are important predators; their larvae feed upon and live in the seeds of a wide variety of plants. In Argentina, there not exists background information concerning the levels of predation of Ipomoea nil (Convolvulaceae) seeds caused by these insects. Thus, the aim of this work was to record the incidence of the species of the genus Megacerus as predators of I. nil seeds, an important weed affecting cotton growing in the irrigation area of Santiago del Estero. Megacerus maculiventris was the only bruchine species identified as predator of this weed. The predation percentage ranged from 0.84 to 15.66% in the agricultural years 2004-2008. It was attested that the number of predated seeds per capsule is independent from the number of seeds per fruit. However, it was proved that the insect predates just one seed per capsule and the highest predation frequency occurs in fruits containing more than three seeds. The levels of predation of I. nil by M. maculiventris are low in relation to those registered in other hosts by bruchines of the genus Megacerus.
Highlights
The cultivation of cotton, Gossypium hirsutum L. (Malvaceae), has a remarkable importance in the provinces of northern Argentina as a development agent of the region’s economy in the primary sector, in the industrial sector, in related services and in the commercial sector of the area of influence, which together represent a large occupation of direct and indirect labor (Bonacic et al, 2006)
In Argentina, there are no records of predation levels of I. nil seeds caused by bruchids, the aim of this study was to determine the species of bruchids that predate seeds of this weed in the cotton agro-ecosystem and evaluate their incidence on the propagule bank
Individuals from I. nil seeds, harvested between the years of 2005 and 2008, were extracted from commercial cotton production lots located in the field of the Estación Experimental Agropecuaria La María- INTA Santiago del Estero, Argentina (28o03’S 64o15’W, elevation 182 above sea level)
Summary
BRUCHINE-PREDATED SEEDS OF Ipomoea nil (L.) ROTH., A COTTON CROP WEED IN SANTIAGO DEL ESTERO, ARGENTINA. The aim of this work was to record the incidence of the species of the genus Megacerus as predators of I. nil seeds, an important weed affecting cotton growing in the irrigation area of Santiago del Estero. Na Argentina, não há registros dos níveis de depredação de sementes de Ipomoea nil (Convolvulaceae) causada por esses insetos. O objetivo deste trabalho foi registrar a incidência das espécies do gênero Megacerus como depredadores de sementes de I. nil, importante planta daninha da cultura de algodoeiro em área de irrigação de Santiago del Estero. Megacerus maculiventris foi a única espécie de bruquídeo identificada como depredadora de sementes dessa planta daninha, tendo a porcentagem de depredação variado de 0,84% a 15,66% nos anos agrícolas de 2004 a 2008. Bruchine-predated seeds of Ipomoea nil (L.) Roth., a cotton crop weed in
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