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Button grass (Dactyloctenium radulans) is a native, widely spread summer grass weed species in Australia. However, limited information is available on the seed germination biology of this species. Experiments were conducted to evaluate the effect of environmental factors on the germination and emergence of two populations of D. radulans. The seeds of these populations were collected separately from Dalby, Queensland and Coleambally, NSW. Seeds were germinated at a range of constant and alternating temperatures (25/15, 30/20, 35/25 and 40/30°C day/night). The greatest seed germination was at a constant temperature of 30°C. Seed germination was reduced at the lowest alternating temperature (25/15°C). Germination of both populations was strongly stimulated by light, suggesting a great amount of emergence of D. radulans on bare ground, such as crop seedbeds. Germination of the D. radulans population collected from a northern cotton farming system (Dalby) was more tolerant to a greater range of salt stress than the population sourced from the south (Coleambally). Seeds of both populations germinated over a wide range of pH, between 4 and 10. However, germination was the greatest in a high pH buffer solution, indicating that the species prefers to germinate in alkaline soil. These results showed that D. radulans seeds possess a wide range of tolerance mechanisms to different environmental stresses. Information obtained in this study will help in developing more sustainable and effective integrated weed management strategies for the control of this weed and weeds with similar responses in summer cropping systems, such as cotton. [ABSTRACT FROM AUTHOR]

An understanding of phenology and reproductive plasticity of a weed species can provide valuable information to manage it precisely. This study evaluated the phenotypic plasticity of feathertop Rhodes grass (Chloris virgata Sw.) where cohorts of four different populations (two from cropping and two from roadside situations) were initiated in early spring (4 September), late spring (4 November), mid-summer (4 January), and early autumn (4 March) in southern New South Wales (NSW), Australia. The team grew individual plants in the absence of competition under natural conditions. Life-history and fitness-related traits of both phenology and morphology were measured, and dry biomass of vegetative and reproductive parts were determined at physiological maturity. Among the four sowing times, the late-spring sowing treatment took the longest time from emergence to the first seed head emergence (70–110 days), while it had the shortest seed maturity period (8–16 days). Length of reproductive and total life period of the four populations differed across the four sowing-time treatments. The plants that emerged in mid-summer had the longest reproductive period (30 days) whereas the early-autumn emerging plants died before the reproductive stage because of the cold temperatures during winter. The mid-summer cohort required slightly longer time (63–85 days) to achieve seed head formation and less time (19–24 days) for seed maturity than those plants that emerged in early or late spring. All the reproductive features were varied by sowing times and population. The number of seed heads (12–15 per plant) and spikelets (12–13 per seed head), as well as the seed head biomass, re-productive biomass allocation pattern, and seed production, generally increased in the mid-summer-emerged cohort. Seed production in the mid-summer (9942 seeds/plant) cohort was 10% and 70% higher than the late spring (8000 seeds/plant) and early spring (3240 seeds/plant) cohorts, respectively. The ratio of reproductive biomass to vegetative biomass increased in the mid-summer sowing times in all populations, and this species displayed true plasticity in reproductive allocation. Additionally, the four populations of feathertop Rhodes grass differed significantly in phenological, vegetative, and reproductive traits, depending on the sowing time. The reproductive fitness of the four populations varied, with the two roadside populations (FELT 04/20 and STURT/16–17) appearing to be better adapted than the two cropping populations (PARK 01/20 and GLEN 03/18). The results from our study could help construct a basic framework for a variety of weed-management tactics to achieve successful control. [ABSTRACT FROM AUTHOR]

Prickly lettuce (Lactuca serriola L.) has become an increasing problem in cereals and lucerne pastures in southern New South Wales, Australia. A better understanding of the biology is needed for improved control. Laboratory and field experiments were conducted to determine dormancy status among L. serriola populations, to evaluate environmental factors affecting seed germination and to determine field emergence patterns. Among 76 L. serriola seed samples collected between 2015 and 2018, more than 59% of the samples had little or no innate dormancy, with germination greater than 80%. However, a further tetrazolium test showed that 42 samples collected in the summer season of 2015-16 differed in their dormancy status, with high levels of initial dormancy up to 75.6% in some populations. Lactuca serriola germinated from 10 C to more than 35 C, with the optimum temperatures being 15–25 C. Light stimulated the germination of L. serriola , while the germination was completely suppressed at 80–110 mM of NaCl. Lactuca serriola germinated well under a range of acidic and alkaline conditions. L. serriola predominately emerged (40–52%) from the soil surface, however, limited emergence also occurred from beyond 5-cm burial depth (up to 1.5%). Emergence in a standing crop was 10 times less than that in a bare soil. L. serriola populations from high and low rainfall zones had similar seasonal emergence patterns in the field, with 69% emergence in late autumn and early winter, 22–26.8% in late winter, 1.4–2.4% in spring in the first year after sowing, little or limited emergence in the second and third year. These results suggest that L. serriola can colonise wide geographical areas. Controlling the autumn and winter cohorts is important to stop seed set. If the seed set is completely prevented, L. serriola can be managed over a minimum of two years due to the relatively short-lived seed life. • Some populations of L. serriola exhibit strong seed dormancy after collection. • It adapts well to a range of temperature, saline, acidic and alkaline conditions. • It is a surface-germinator, but it can emerge (up to 1.5%) from deeper burial depths. • Most field emergence occurs in late autumn and early winter. • Crop competition reduced its emergence tenfold compared to bare soil. [ABSTRACT FROM AUTHOR]