Emergence and early establishment of Chondrilla juncea L. (skeleton weed) in the Western Australian wheatbelt

When sown over consecutive years at two sites in the Western Australian wheatbelt, a maximum of 34.5% of viable Chondrilla juncea seeds gave rise to emerged seedlings. During the early winter months at one site, waterlogging on a duplex soil type led to an almost complete failure of emergence. Very low levels of seed persistence (maximum 3.1%) between years were noted. The protection provided by stubble enhanced the survival of C. juncea seedlings which emerged during May, but for seedlings which emerged later, the effects of stubble upon seedling survival were strongly dependent upon the abundance of the red-legged earth mite (Halotydeus destructor) At the observed densities of winter annuals, the presence of seedlings and young plants appeared to reduce seedling mortality in C. juncea. Young plants of C. juncea were highly susceptible to simulated cultivation practices until 12 weeks following emergence. It is argued that seedling establishment of C. juncea is most likely to occur during the pasture phase of crop/pasture rotations in the Western Australian wheatbelt and that pastures immediately following cropping years are most prone to invasion.