Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/11/2007
Publication Date: 11/7/2007
Citation: Williams, R.D., Bartholomew, P.W. 2007. Insect seed predation as a factor in Italian ryegrass persistence[abstract]. American Society of Agronomy Abstracts. 271-19. Interpretive Summary: Abstract only.
Technical Abstract: Italian ryegrass can be a productive and high-quality cool-season forage. However, as an annual, it does not form a persistent seed bank and needs to be managed to produce sufficient seed for effective re-establishment. Before the re-seeding dynamics of Italian ryegrass can be modeled, an understanding of seed production, dispersal and predation are necessary. Here we examine insect predation of ryegrass seed over a 12-month period from May 2006 to June 2007. Seed cards (5 by 10 cm) were constructed from coarse sand paper, lightly sprayed with adhesive and 30 ryegrass seed set on their surface firmly enough to transport the seed cards to and from the field, but loose enough to allow insect removal of the seed. Forty cards were distributed in a warm-season grass pasture that had been seeded to Italian ryegrass three years prior to the present study. The grass was maintained by frequent cutting to a height of 10 cm. Cards were held in place on the soil surface with wire pegs and covered wire mesh cages (to exclude rodents). Seed cards were collected weekly and replaced with fresh cards. Seed predation was both temporally and spatially variable. Most predators noticed in the field were harvester ants, but other predators (eg. crickets) were also observed. Weekly mean seed predation ranged from 6 to 86 % over the 12-month period. Although greater predation was expected during the summer, predation was the greatest during the winter. Mean predation over the winter months was 53% as compared to 34% in the summer and 26% in the fall. This information coupled with general seed survival data will provide a clearer understanding of the transient soil-seed population.