Abstract
Witchgrass (PanicumcapillareL.) is a summer growing grass weed species and is increasing its prevalence in southern Australia. A better understanding of the seed biology is needed to effectively manage this weed. A series of field and laboratory studies were conducted to determine seed germination factors, field emergence patterns, and soil seedbank longevity. Witchgrass germination was stimulated by light and it germinated better at temperature over 20°C, with 93–100% germination at the two constant temperatures of 20 and 30°C, and the two alternating day/night temperatures of 30/25 and 35/25°C. It is highly tolerant to moisture stress at germination, with 2–7% germination even at −0.48 Mpa. Witchgrass seed lost 47–68% viability after 12 months of burial in the soil, however the seed persisted for more than 4 years if buried at 10 cm in the soil. Witchgrass emergence in southern New South Wales (NSW) commenced in mid spring (early October), with peak emergence of 63–83% in November and then significantly reduced to 16–37% emergence in December. Little emergence (<1%) occurred in the summer months from January to February. These results provide useful information for designing effective management strategies and the optimum timing of control. Climate change could favor the phenological development and the further spread of this weed, which present new challenges for its effective management. Further study is needed to investigate the impact of climate change on the biology, spread, and management of witchgrass.
Highlights
The genus Panicum is one of the largest genera in the Poaceae, with more than 500 species worldwide, mostly occurring in the tropics (Crins, 1991; Aliscioni et al, 2003; Byng, 2014)
Witchgrass (Panicum capillare L.) is an annual grass belongs to the genus Panicum and it is indigenous to North America (Baskin and Baskin, 1986)
The highest germination was achieved at temperatures over 20◦C, with 93–100% germination at the two constant temperatures of 20 and 30◦C, and the two alternating temperatures of 30/25 and 35/25◦C in a 12-h light/dark cycle
Summary
The genus Panicum is one of the largest genera in the Poaceae, with more than 500 species worldwide, mostly occurring in the tropics (Crins, 1991; Aliscioni et al, 2003; Byng, 2014). Panicum species are widespread in Australia, with 24 indigenous and nine introduced species (CHAH (Council of Heads of Australasian Herbaria), 2021) These Panicum species are among the key summer weeds in Australia (Llewellyn et al, 2016). Witchgrass (Panicum capillare L.) is an annual grass belongs to the genus Panicum and it is indigenous to North America (Baskin and Baskin, 1986) It is a summer active growing C4 grass weed species and has invaded many non-native ranges throughout the world, from subtropical to temperate areas. These include Asia, South America (Argentina and Chile), New Zealand, Australia, Morocco, Russia, and many European countries (Clements et al, 2004). In Australia, it can be confused with a native perennial grass, Hairy Panic (Panicum effusum R.Br.) (Phillips, 2010)
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