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The potential impact of postdispersal seed predation by the field cricket, Teleogryllus emma (Ohmachi et Matsuura), on the seedling emergence of Italian ryegrass ( Lolium multiflorum Lam.), a non-native grass weed in Japan, was determined. The relationship between cricket density and the proportion of seedling emergence was investigated by conducting manipulative experiments in duplicate, using enclosures. One-thousand seeds of Italian ryegrass were exposed to adult crickets at different densities (zero, one, two, four and eight individuals per 2.25 m2 enclosure) for 2 weeks. The proportion of seedling emergence decreased with increasing cricket density. The proportion of seedling emergence in the enclosures without the crickets was 90.9-97.2%, whereas the seedling emergence in the enclosures with eight crickets greatly decreased, to 0.5-2.5%. These results suggest that postdispersal seed predation by T. emma can substantially decrease the abundance of Italian ryegrass at an early life stage and reduce its population in environments with a high density of crickets. [ABSTRACT FROM AUTHOR]

Italian ryegrass ( Lolium multiflorum Lam.) is an exotic winter annual weed that recently has seriously infested wheat fields in central Japan. To understand the influence of tillage systems on the germination ecology and seedbank dynamics of naturalized Italian ryegrass, we compared the fate of the seeds that were after-ripened in the soil with that of the seeds on the soil surface, and then examined the germination characteristics of the seeds retrieved from both treatments by germination tests in both a light/dark (12 h photoperiod) condition and in constant darkness. The seedling emergence was greater initially for the seeds after-ripened on the soil surface than for the seeds in the soil. The component of emergent seeds after-ripened on the soil surface increased as time passed during the summer, whereas that of emergent seeds in the soil scarcely increased. This contrasting emergence was, in part, attributable to the ability of the seeds to germinate at higher temperatures in the light/dark condition than in constant darkness. These results suggest that untilled systems, which leave many seeds on the soil surface, might promote the rapid depletion of Italian ryegrass seeds through germination before wheat sowing in early winter. In contrast, seed burial by tillage might inhibit the germination of the seeds and form a large transient seed bank available to germinate during the wheat-growing season. [ABSTRACT FROM AUTHOR]