Postdispersal Predation of Velvetleaf (Abutilon theophrasti) Seeds

Abstract

Studies were conducted from 1989 to 1993 in continuous no-tillage and moldboard plow corn fields to describe rates of velvetleaf seed predation with time and with seed density, and to identify principal seed predators. Rates of seed loss from the soil surface averaged 1 to 57% day−1and were equivalent in the two tillage systems. Predator populations were the same in no-tillage and moldboard plow fields. The predation rate was generally low in winter months, increased in mid-summer, and declined in late summer. In 2 of the 4 yr, predation increased in October and November. The predation rate was described by an exponential decay function of seed density, with high rates of seed loss at low densities and leveling off to a nearly constant level at densities above 600 seeds m−2. Predation was highest where seed access was not restricted, and exclosures of 6.5 and 1.6 cm2reduced predation up to 15 and 52%, respectively. Mice were important predators in the field. In laboratory feeding studies, the carabid beetleAmara cupreolata, the slugsArion subfuscusandDeroceras reticulatum, and cutworms (Agrotis ipsilon) consumed imbibed velvetleaf seeds.Amara cupreolataand A.subfuscuswere the only predators to damage unimbibed velvetleaf seeds.