Weed seed predation in a phenologically late crop

Seed predation of weed seeds in crops depends on the seasonal overlap between seed availability and the activity period of the predators. Published data show that the activity period of seed predators is directly related to canopy cover. In phenologically early crops, such as cereals, maturation of leaves results in a decreasing cover prior to weed seed shed, resulting in lower seed losses than maximally possible. We hypothesised that there would be better temporal overlap in sugar beet, a phenologically late crop. The pattern of predation of Chenopodium album L. seeds was consistent over fields and years, low in July and August and gradually increasing until harvest in September/November. The patterns of seed production and shed, measured using seed traps, differed among weed species. The proportion of annual seed losses by predators calculated from these measurements ranged from 0.26 to 0.83, depending on the duration of seed exposure on the soil surface. As expected, sugar beet had better temporal overlap between predator activity and weed seed production, which may cause higher seed losses than previously reported for any other annual crop.