Effects of seeding density and spatial distribution of oat plants on colonization and development of Oscinella frit (Diptera: Chloropidae).
Field and laboratory trials were conducted in southern England to study the effects of seeding density and row spacing of oats on colonisation of seedlings by Oscinella frit (L.) and on subsequent population development. Consistently more flies were caught in water traps over dense plantings than over sparse ones. At the same density of plants per unit area, significantly more flies were caught in plots with closely spaced than with widely spaced rows. Similar results were obtained in the laboratory with 'artificial' oat plants of different densities and row spacings. Most eggs were laid per plant in the sparsest plantings and least in the densest plantings although, per unit area of crop, most eggs were laid in the densest and least in the sparsest plantings. More eggs were laid on plants in closely spaced rows in field plots and in seed trays in the laboratory than on plants of equivalent densities in more widely spaced rows. When soil moisture was limiting, larval penetration into plants in the field and in the laboratory was more successful where plants were crowded within the row than where they were more isolated. Most larvae died and the lightest pupae were produced in the sparsest plantings, and least mortality and heaviest pupae occurred in the densest plantings, probably due to greater competition for insufficient food in the former.