SURVIVAL AND DORMANCY OF PURPLE NUTSEDGE (CYPERUS-ROTUNDUS) TUBERS

Survival and dormancy of purple nutsedge tubers has not been studied q uantitatively. Yet this is fundamental to our understanding of the pop ulation dynamics of this highly noxious weed. Field studies were condu cted to determine the effect of age on tuber survival and dormancy. A modified exponential decay function accurately described the age-depen dent decline in tuber survival. This model is biologically meaningful, has good statistical properties, and can describe a wide range of res ponses. Tuber population half-life was 16 mo, and the predicted longev ity (99% mortality) was 42 mo. Burial depth at 8 and 23 cm had no sign ificant effect on survival or dormancy. Tuber dormancy increased with age. After 18 mo, the proportion of dormant tubers in the surviving po pulation was two-and-one-half times higher than in the 3-mo-old popula tion. We report for the first time that tubers were able to enter a st ate of secondary dormancy after sprouting. The finding that tubers per sist after sprouting has important implications for population dynamic s of this species. This is also the first report of tuber predation by the larvae of a billbug.