Bruchine-Predated Seeds of Ipomoea nil (L.) Roth., A Cotton Crop Weed in Santiago Del Estero, Argentina

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